Ionic Liquid Electrospray Thrusters(ILETs)are well suited for micro-nano satellite applications due to their small size,low power consumption,and high specific impulse.However,the limited thrust of a single-emitter IL...Ionic Liquid Electrospray Thrusters(ILETs)are well suited for micro-nano satellite applications due to their small size,low power consumption,and high specific impulse.However,the limited thrust of a single-emitter ILET restricts its use in space missions.To optimize the performance of ILETs and make them suitable for a wider range of space missions,we designed a Circular-emitter ILET(CILET)to convert a one-dimensional(point)emission into a twodimensional(line)emission.The CILET can self-organize multiple Taylor cones simultaneously.The cones were photographed and the axial emission currents were measured under different voltage and pressure difference conditions with a CILET experimental system.The emission can be divided into two stable states and one unstable state based on the flow and current characteristics.The current in Stable state Ⅰ increases non-linearly with the voltage,while that in Stable state Ⅱ is nearly linear with respect to the voltage.The number of cones increases with the voltage in stable states,while the cones become short and crowded under high-voltage conditions.The variation law of the number of cones can be explained with the self-organization theory.The variation in the current exhibits a good correlation with the number of cones.This study demonstrates the feasibility of circular emitters and experimentally indicates that the emission current is improved by approximately two orders of magnitude compared to that of a single capillary.展开更多
Exploring electrode materials with larger capacity,higher power density and longer cycle life was critical for developing advanced flexible lithium-ion batteries(LIBs).Herein,we used a controlled two-step method inclu...Exploring electrode materials with larger capacity,higher power density and longer cycle life was critical for developing advanced flexible lithium-ion batteries(LIBs).Herein,we used a controlled two-step method including electrospraying followed with calcination treatment by CVD furnace to design novel electrodes of Si/Si_(x)/C and Sn/C microrods array consisting of nanospheres on flexible carbon cloth substrate(denoted as Si/Si_(x)/C@CC,Sn/C@CC).Microrods composed of cumulated nanospheres(the diameter was approximately 120 nm)had a mean diameter of approximately 1.5μm and a length of around 4.0μm,distributing uniformly along the entire woven carbon fibers.Both of Si/Si/Si_(x)/C@CC and Sn/C@CC products were synthesized as binder-free anodes for Li-ion battery with the features of high reversible capacity and excellent cycling.Especially Si/Six/C electrode exhibited high specific capacity of about 1750 mA∙h∙g^(−1)at 0.5 A∙g^(−1)and excellent cycling ability even after 1050 cycles with a capacity of 1388 mA∙h∙g^(−1).Highly flexible Si/Si_(x)/C@CC//LiCoO_(2)batteries based on liquid and solid electrolytes were also fabricated,exhibiting high flexibility,excellent electrical stability and potential applications in flexible wearable electronics.展开更多
The investigation of reaction kinetics is the key to understanding the nature of reaction processes.However,monitoring fast photochemical reactions by mass spectrometry remains challenging.Herein,we developed an optic...The investigation of reaction kinetics is the key to understanding the nature of reaction processes.However,monitoring fast photochemical reactions by mass spectrometry remains challenging.Herein,we developed an optical focusing inductive electrospray(OF-iESI)mass spectrometry platform for real-time and in-situ photoreaction monitoring.Coaxial irradiation from back of nanoelectrospray emitter with a taper section was utilized,so the emitter could act as optical lens to help achieving much larger optical power density at emitter tip compared to other sections,which allowed for in-situ reaction monitoring of photoreactions.Through theoretical calculations,the highest optical power density region volume was ca.45 nL.We also integrated a controller for the laser source(450 nm),enabling the modulation of pulse duration(>1 ms).This facilitates the study of photochemical reaction kinetics.The in-situ capability of this device was proved by capturing the short-lived photogenerated intermediates during the dehydrogenation of tetrahydroquinoline.This device was further used to investigate the kinetics of triplet energy transfer based Paternò-Büchi reaction.The reaction order has hitherto remained undetermined while the result of OF-iESI suggested it followed pseudo-second-order reaction kinetics.The short-lived donor-acceptor collision complex intermediate was also successfully identified by tandem mass spectrometry.展开更多
The electrospray thruster supplied by ionic liquid is a promising micro-propulsion thruster with small size and precise thrust, which can emit both cations and anions to achieve self-neutralization. In order to furthe...The electrospray thruster supplied by ionic liquid is a promising micro-propulsion thruster with small size and precise thrust, which can emit both cations and anions to achieve self-neutralization. In order to further investigate the effect of ion solvation energy on the evaporation of cations and anions from ionic liquid under the action of a uniform electric field, this paper establishes a transient Electrohydrodynamic (EHD) model for free ionic liquid droplets undergoing ion evaporation. The dynamic processes of droplet deformation and ion evaporation are simulated. And the study further focuses on the influence of different ion solvation energies for cations on the droplet morphology and the ion evaporation characteristics at the positively charged end and negatively charged end of the droplet. The results indicate that, when the ion solvation energy for cations is higher than that of anions, it will cause the ion evaporation at the positively charged end of the droplet to lag behind the ion evaporation at the negatively charged end. And the higher the ion solvation energy for the cations, the longer the evaporation lag time at the positively charged end of the droplet, which will lead to a higher peak of surface charge density that can be reached, resulting in a larger evaporation current and sharper droplet stretching deformation. Additionally, the peak surface charge density of the positively charged end of the droplet is linearly related to the ion solvation energy for cations, while the peak surface charge density of the negatively charged end remains almost unchanged and is not significantly affected by the ion solvation energy for cations.展开更多
Accurate determination of lung cancer margins at the molecular level is of great significance to determine the optimal extent of resection during surgical operation and reduce the risk of postoperative recurrence.In t...Accurate determination of lung cancer margins at the molecular level is of great significance to determine the optimal extent of resection during surgical operation and reduce the risk of postoperative recurrence.In this study,internal extractive electrospray ionization mass spectrometry(i EESI-MS)was used to trace potential molecular tumor margins in lung cancer tissue.Molecular differential model for the determination of lung cancer tumor margin was established via partial least-squares discriminant analysis(PLS-DA)of iEESI-MS data collected from lung tissue pieces within cancer tumor area and iEESI-MS data collected from lung tissue pieces outside cancer tumor area.Proof-of-concept data demonstrate that the developed molecular differential model yields ca.1-2 mm wider potential molecular tumor margin of a lung cancer compared to the conventional histological analysis,showing promising potential of iEESI-MS to increase the accuracy of tumor margins determination and lower risk of lung cancer postoperative recurrence.Furthermore,our results revealed that creatine and taurine showed positive correlations with lung cancer.展开更多
Traditional electrospray ionization tandem mass spectrometry(ESI-MS^(n))has been a powerful tool in diverse research areas,however,it faces great limitations in the study of protein-small molecule interactions.In this...Traditional electrospray ionization tandem mass spectrometry(ESI-MS^(n))has been a powerful tool in diverse research areas,however,it faces great limitations in the study of protein-small molecule interactions.In this article,the state-of-the-art temperature-controlled electrospray ionization tandem mass spectrometry(TC-ESI-MS^(n))is applied to investigate interactions between ubiquitin and two flavonol molecules,respectively.The combination of collision-induced dissociation(CID)and MS solution-melting experiments facilitates the understanding of flavonol-protein interactions in a new dimension across varying temperature ranges.While structural changes of proteins disturbed by small molecules are unseen in ESI-MS^(n),TC-ESI-MS^(n)allows a simultaneous assessment of the stability of the complex in both gas and liquid phases under various temperature conditions,meanwhile investigating the impact on the protein’s structure and tracking changes in thermodynamic data,and the characteristics of structural intermediates.展开更多
Selenium is one of the important trace elements in the human body.Its deficiency will directly affect human health.With people's attention to health,the content of selenium in food has gradually attracted attentio...Selenium is one of the important trace elements in the human body.Its deficiency will directly affect human health.With people's attention to health,the content of selenium in food has gradually attracted attention.However,detecting selenium compounds in complex samples remains a challenge.In this work,we built an online heating-reaction device.This device combines the electrospray extraction ionization mass spectrometry(EESI-MS)with the heating reaction device,which can simultaneously detect various selenium compounds in complex liquid samples.Under acidic conditions,the sample was heated and catalyzed by a heating reaction device,so that the SeO~(2-)_(3)and O-phenylenediamine(OPD)could generate 1,3-dihydro-2,1,3-benzoselenadiazole.Based on the above reactions,we can detect organic selenium,inorganic selenium and other compounds in liquid samples by organic mass spectrometry.In this experiment,we determined the content of three forms of selenium:selenomethionine(SeMet),l-selenocystine(SeCys(2)),and sodium selenite.The calibration curves for SeMet,SeCys(2),and sodium selenite showed strong linearity within a range of 0.50-50.00μg/L.The limits of detection(LOD)for the three compounds were 0.22,0.27,and 0.41μg/L,respectively.The limits of quantification(LOQ)were 0.68,0.81,and 1.23μg/L,respectively.Spiked recoveries at three levels ranged from 98.8%to 106.1%.In addition,this method can simultaneously detect three selenium compounds and three other specific chemical components in tea infusion samples,providing a rapid and efficient method for identifying tea quality.展开更多
To explore the feasibility of electrospray-based additive manufacturing for thin-film fabrication in zero-or microgravity environments,we conducted numerical simulations of charged droplet behavior under zero-gravity ...To explore the feasibility of electrospray-based additive manufacturing for thin-film fabrication in zero-or microgravity environments,we conducted numerical simulations of charged droplet behavior under zero-gravity conditions,followed by ground-based experimental validation using an anti-gravity electrospray(AG-ES)strategy.First,simulations of charged droplet deposition during the electrospray process showed that the presence or absence of gravity did not significantly affect deposition behavior.Second,simulations of droplet-substrate collisions indicated that the presence of an electric field could reduce the risk of droplet splashing.Third,simulations of droplet coalescence under zero-gravity conditions demonstrated that an electric field could promote the coalescence of charged droplets.An AG-ES experimental platform featuring an inverted nozzle-substrate configuration was constructed on the ground.Comparative experiments using Rhodamine B solution and TiO_(2)nanoparticle dispersions were performed in both AG-ES and conventional electrospray(ES)modes.The results indicated that the spray cone angle,deposition area,and film morphology were comparable between the two modes.Finally,multilayer alternating-current electroluminescent(ACEL)devices were fabricated via AG-ES using ZnS:Cu/poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP),BaTiO_(3)/polyvinylpyrrolidone(PVP),and silver nanowire(AgNW)inks,achieving a maximum luminance of 66.2 cd/m^(2).This study demonstrates the potential of the electrospray process for functional thin-film fabrication under microgravity conditions.展开更多
The ionic liquid electrospray thruster is a microminiature thruster that can be applied on a micro or nano-satellite,and its highly energy-efficient,compact,modular system can be used for both main propulsion and alti...The ionic liquid electrospray thruster is a microminiature thruster that can be applied on a micro or nano-satellite,and its highly energy-efficient,compact,modular system can be used for both main propulsion and altitude control.In this study,an ionic liquid electrospray thruster with a 100-tip emitter configuration is tested primarily to examine the difference in performance of the thruster at different angles with time-of-flight(TOF)mass spectrometry tests.In the experiment,it was measured that the half-angle of the thruster plume angle emission was in the range of−60 degrees to+65 degrees.Accordingly,the measurement range was set from−50 degrees to+50 degrees,with an interval of 10 degrees.Relative to the results of the 0 degree current curve,the positive mode is relatively homogeneous at all angles of the operating mode.In the negative mode,for n 2 ions,the negative angle region accounts for a larger proportion and the positive angle region accounts for a smaller proportion,which makes a significant difference to the specific impulse of the two regions.The range of the specific impulse at different angles is 3776-4401 s under the typical working condition of+2.5 kV.Under−2.5 kV,the range of the specific impulse at different angles is 3309-4654 s.This research quantifies the angular performance variations of the ionic liquid electrospray thruster,offering valuable data to improve its design and operational reliability for precise propulsion and altitude control in satellite applications.展开更多
The ginkgo terpenoids including bilobalide and ginkgolides are the main pharmaceutical components in the leaves or extracts of Ginkgo biloba L. In this paper, the analysis of bilobalide and ginkgolides in leaves of Gi...The ginkgo terpenoids including bilobalide and ginkgolides are the main pharmaceutical components in the leaves or extracts of Ginkgo biloba L. In this paper, the analysis of bilobalide and ginkgolides in leaves of Ginkgo biloba L. by high performance liquid chromatography (HPLC)-electrospray ionization (ESI)-mass spectrometry (MS) was carried out. The separation was performed on Inertsil ODS3 column with methanol-water (36:64) as mobile phase, with 1 mL·min -1 of flow rate at 35℃. Then the mass spectrum analysis was conducted by ZMD micromass electrospray ionization (ESI)-mass spectrometer (MS). The HPLC total ion chromatogram and selected ion chromatogram (with 325, 407, 423, 439 of m/z) of the sample and ESI-/MS mass spectra of the peaks in the chromatograms were obtained. So bilobalide, ginkgolide A, B, C and J in Ginkgo biloba L. leaves were identified. The method is easy and rapid, with a good accuracy.展开更多
An ionic liquid(IL)electrospray thruster was developed for application in micro-nano satellites or gravitational wave detectors.The thruster employed a porous ceramic emitter with seven emitter strips located on its e...An ionic liquid(IL)electrospray thruster was developed for application in micro-nano satellites or gravitational wave detectors.The thruster employed a porous ceramic emitter with seven emitter strips located on its emission surface.Without any liquid-supply device,IL was delivered through porous media to emitter strips via capillary effect.Multiple emission sites then formed at the tip of each strip.A charged beam of up to 350μA(with a current density of 540μA cm^(-2))was stably produced in the negative mode.However,in the positive mode,a corona was observed which could prevent the thruster from emitting larger current.A time-of-flight mass spectrometer with significantly improved signal-to-noise ratio was built,which was used to obtain the mass distribution of the beam of the thruster.A retarding potential analysis was also performed.The test results showed that the thruster worked in the pure-ion regime,and delivered a maximum thrust of 67.1μN with specific impulses of 3952 s and 3117 s in the positive and negative modes,respectively.展开更多
In order to meet the demand of CubeSats for low power and high-performance micro-propulsion system,a porous ionic liquid electrospray thruster prototype is developed in this study.1010 conical emitter arrays are fabri...In order to meet the demand of CubeSats for low power and high-performance micro-propulsion system,a porous ionic liquid electrospray thruster prototype is developed in this study.1010 conical emitter arrays are fabricated on an area of 3.24 cm^(2) by computer numerical control machining technology.The propellant is 1-ethyl-3-methylimidazolium tetrafluoroborate.The over-all dimension of the assembled prototype is 3 cm×3 cm×1 cm,with a total weight of about 15 g(with propellant).The performance of this prototype is tested under vacuum.The results show that it can work in the voltage range of±2.0 kV to±3.0 kV,and the maximum emission current and input power are about 355 lA and 1.12 W.Time of Flight(TOF)mass spectrometry results show that cationic monomers and dimers dominate the beam in positive mode,while a higher proportion of higher-order solvated ion clusters in negative mode.The maximum specific impulse is 2992 s in positive mode and 849 s in negative mode.The thrust is measured in two methods:one is calculated by TOF results and the other is directly measured by high-precision torsional thrust stand.The thrust(T)obtained by these two methods conforms to a certain scaling law with respect to the emis-sion current(I_(em))and the applied voltage(V_(app)),following the scale of T-Iem_(Vapp)^(0.5),and the thrust range is from 2.1 lN to 42.6 lN.Many thruster performance parameters are significantly different in positive and negative modes.We speculate that due to the higher solvation energy of the anion,more solvated ion clusters are formed rather than pure ions under the same electric field.It may help to improve thruster performance if porous materials with smaller pore sizes are used as reservoirs.Although there are still many problems,most of the performance parameters of ILET-3 are good,which can theoretically meet the requirements of CubeSats for micro-propulsion system.展开更多
As a novel micro-propulsion system for small satellites(from micro to nano),the ionic liquid electro spray propulsion system is a promising candidate.However,performance measurement and evaluation of the Ionic Liquid ...As a novel micro-propulsion system for small satellites(from micro to nano),the ionic liquid electro spray propulsion system is a promising candidate.However,performance measurement and evaluation of the Ionic Liquid Electrospray Thruster(ILET)is one of the most challenging issues for practical application,due to the difficulties in the development of a prototype and direct measurements of micro-thrust and small flow rate.To address this issue,a Modular Ionic Liquid Electrospray Thruster(MILET)prototype is constructed,and a diagnostic system for thrust and mass flow rate is specially developed based on an analytical balance method.With the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as the propellant,a series of experiments is carried out on the MILET prototype under a wide operating condition through changing the applied voltage to control the thrust.Under different applied voltages,the thrust and the mass flow rate of the propellant are directly measured.The propulsive performance parameters of the thruster,such as thrust,specific impulse,thrust-to-power ratio,thruster efficiency,etc.,are comprehensively analyzed.Then,a performance comparison is made between the MILET and other representative ILETs.With a relatively low applied voltage ranging from 1550 V to 2000 V,the MILET achieves a quasi-constant specific impulse of 1263 s with the averaged thrust-to-power ratio of 65.2μN/W and thruster efficiency of 40.7%.The performance of ILET is also compared with other typical electric propulsions.The results demonstrate that the ILET exhibits an excellent ability of minimalization with high specific impulse and thruster efficiency,which guarantees a great superiority in micro propulsions.Finally,the ways to further improve the performance of ILET are discussed,which further confirms the potential prospect of ILET.The present result helps to advance the development and application of ILET.展开更多
Mass spectrometry imaging (MSI) technology can simultaneously obtain the spatial distribution of thousands of chemical compounds and has unique advantages compared to other techniques that allow mapping the surface of...Mass spectrometry imaging (MSI) technology can simultaneously obtain the spatial distribution of thousands of chemical compounds and has unique advantages compared to other techniques that allow mapping the surface of bio-tissue. Here, we combined an air flow-assisted desorption electrospray ionization (AFADESI) MSI device with a high-resolution mass spectrometer to optimize the system parameters and achieve more accurate spatial distribution characteristics for compounds of interest while investigating bio-tissue sections. The platform set-up, required instrumentation, sample pretreatment, parameter optimization and bio-tissue characterization are described and discussed.Finally, the parameter conditions that can provide optimal ionic intensity and enhanced resolution were confirmed. The reasonable resolution and sensitivity improvements of AFADESI-MSI have been achieved through tandem a high-resolution mass spectrometer system, therefore, it would be a promising technique for the bio-tissue imaging analysis.展开更多
In present study, a simultaneous electrospinning and electrospraying（SEE） process was employed to produce microclusters of TiO2 nanoparticles and interlock them in nanofibrous network. The photocatalytic composite m...In present study, a simultaneous electrospinning and electrospraying（SEE） process was employed to produce microclusters of TiO2 nanoparticles and interlock them in nanofibrous network. The photocatalytic composite membranes（PCMs） were fabricated by electrospraying TiO2 nanoparticle suspension into microcluster form that dispersed and entrapped within nylon-6 electrospun fiber membrane. Three PCMs membrane with TiO2 content of 52.0, 83.6,and 91.7 wt.% were successfully fabricated. The membrane consisted of TiO2 microclusters,ranging in sizes from around 0.3 to 10 μm, distributed uniformly within the nylon-6 nanofibrous network. PCMs photocatalytic activity against Methylene Blue（MB） in aqueous solution showed more than 98% MB removal efficiency after 120 min of photocatalytic oxidation（PCO） for all PCMs. For PCM with the highest TiO2 content tested for 5 PCO cycles, it was found that most of their TiO2 content remained incorporated within the nanofibrous structure. The concept of nanoparticles clusters entrapment with SEE fabrication employed here provide a simple and effective method for reducing detachment of nanostructure phase from nanocomposite membrane.展开更多
Electrospray ionization mass spectrometry（ESI-MS） was applied simultaneously in determining norditerpenoid alkaloids from the roots of Aconitum sinomantanum Nakai （RAS） based on molecular mass information. The tan...Electrospray ionization mass spectrometry（ESI-MS） was applied simultaneously in determining norditerpenoid alkaloids from the roots of Aconitum sinomantanum Nakai （RAS） based on molecular mass information. The tandem mass spectra（ ESI-MS^n） provided the alkaloidal structural information, through which the existence of these alkaloids was further confirmed. Accordingly, six known norditerpenoid alkaloids were simultaneously determined on the basis of their ESI-MS^n spectra. Furthermore, based on the diagnostic fragmentation pathways of alkaloidal MS^n, a rapid method for direct detection and characterization of alkaloids from an ethanolic extract of RAS was described.展开更多
The high-efficiency fabrication of high-quality microcapsules containing epoxy is crucial to the further development of the potential practical self-healing epoxy systems based on microencapsulated two-part epoxy-amin...The high-efficiency fabrication of high-quality microcapsules containing epoxy is crucial to the further development of the potential practical self-healing epoxy systems based on microencapsulated two-part epoxy-amine chemistry.Herein,a novel microencapsulation technique based on non-equilibrium droplets via integrating electrospraying and interfacial polymerization(ES-IP)was established to efficiently microencapsulate epoxy monomers.The ES-IP technique,consisting of three continuous steps,i.e.electrospraying to massively generate droplets,enwrapping every single droplet through instant interfacial polymerization,and thickening shell at an elevated temperature,has great flexibility to regulate the microencapsulation process and the microcapsule quality.The fabricated core-shell structured epoxy microcapsules(Ep-MCs)were comprehensively characterized for their properties,showing that they have high cleanness with rare impurities,controllable and tunable size,good thermal stability and tightness,and high effective core fraction.The high-quality Ep-MCs were adopted to formulate a self-healing epoxy based on the microencapsulated epoxy-amine chemistry.The highest healing efficiency,in terms of the recovered mode I fracture toughness,of 110±17%was achieved after being healed at room temperature(~25℃)for 48 h.While the developed ES-IP technique facilitates the microencapsulation technique based on non-equilibrium droplets,the fabricated high-quality Ep-MCs greatly promote the further developments of the practical self-healing materials.展开更多
The electrospray thruster is becoming popular in space propulsion due to its low power and high specific impulse.Before this work,an electrospray thruster based on a porous emitter was developed.In order to achieve la...The electrospray thruster is becoming popular in space propulsion due to its low power and high specific impulse.Before this work,an electrospray thruster based on a porous emitter was developed.In order to achieve larger and more stable thrust,the thruster was redesigned,and the influence of the space between strips on thrust was studied.Four types of emitter were tested,and they had 1,3,4 and 14 emitter-strips on the emission surface of the same size respectively.According to the experimental results,the maximum extraction voltage and emission current of the four thrusters are different under stable operational conditions.The measured stable emission currents and extraction voltages were-500μA/-5000 V,-1570μA/-3800 V,-1200μA/-3800 V,and-650μA/-4500 V,respectively.Increasing the number of strips may not result in the emission current increasing,but changing the stable operational range of the emission current per strip and the extraction voltage.The maximum stable operational extraction voltages of 3 and 4 emitter-strips are lower than those of 1 and 14 emitter-strips,but the emission currents are higher than those of 1 and 14 emitter-strips.Time-of-flight mass spectrometry was used to analyze the mass distribution and obtain the performance of the thruster in the case of thrusters with 1 and 3 emitter-strips.Both of their plumes were composed of very small ion cluster(the pure-ion regime),and their thrusts were 80.1μN,219.2μN with specific impulses of 5774 s,5047 s,respectively.展开更多
A study was conducted regarding the effect of concentration of poly (vinylidene fluoride) (PVDF)/N,N-dimethylformamide (DMF) and PVDF/DMF/acetone solutions on the transition between electrospray and electrospinning an...A study was conducted regarding the effect of concentration of poly (vinylidene fluoride) (PVDF)/N,N-dimethylformamide (DMF) and PVDF/DMF/acetone solutions on the transition between electrospray and electrospinning and on the formation of the ? and ? crystalline phases of PVDF. The crystalline phases present in the samples, crystallinity and morphology were determined by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. Low concentration solutions resulted in films consisting of small droplets (electrospray) containing predominantly the ? phase. High concentration solutions resulted in a non-woven mesh of nano-to-micron diameter fibers (electrospinning) containing exclusively the ? phase. These results showed that, the formation of this phase in the electrospinning is related mainly to the solvent evaporation rate, and not to drawing experienced by the polymer during the process. Solvent type affected the amount of crystalline phase present, the boundary concentration between the two processes and the average diameter of fibers. Meshes processed by electrospinning display a degree of crystallinity higher than the films obtained by electrospray.展开更多
Hypromellose acetate succinate(HPMCAS) microparticles containing the poorly-water soluble drug celecoxib(CEL) were prepared by electrospraying intended for oral drug delivery. Various solvent mixtures with different s...Hypromellose acetate succinate(HPMCAS) microparticles containing the poorly-water soluble drug celecoxib(CEL) were prepared by electrospraying intended for oral drug delivery. Various solvent mixtures with different solubility for CEL and HPMCAS were used to induce changes in the polymer structural conformation of the microparticles. The performance of the prepared microparticles was evaluated by studying the solid state from, particle size and morphology, radial drug distribution and drug release. CEL was amorphous in all electrosprayed HPMCAS microparticles. The particle size and morphology was dependent on the solubility of HPMCAS in the solvent mixture used with poorer solvents resulting in smaller microparticles with rougher appearance. The CEL distribution on the particles surface was relatively homogeneous and similar for all microparticles. Drug release from the microparticles was observed at a higher rate depending on the solubility of HPMCAS in the solvent used for electrospraying, and in all cases an at least 4-fold higher rate was observed compared with the crystalline drug. Drug precipitation from the supersaturated solution was inhibited by HPMCAS for all microparticles based on its parachute effect while crystalline CEL did not reach supersaturation. This study demonstrated that electrospraying can be used to produce microparticles with tailored properties for pharmaceutical application by adjusting solvent selection.展开更多
基金co-supported by the National Key R&D Program of China(No.2020YFC2201001)the Shenzhen Science and Technology Program,China(No.20210623091808026)。
文摘Ionic Liquid Electrospray Thrusters(ILETs)are well suited for micro-nano satellite applications due to their small size,low power consumption,and high specific impulse.However,the limited thrust of a single-emitter ILET restricts its use in space missions.To optimize the performance of ILETs and make them suitable for a wider range of space missions,we designed a Circular-emitter ILET(CILET)to convert a one-dimensional(point)emission into a twodimensional(line)emission.The CILET can self-organize multiple Taylor cones simultaneously.The cones were photographed and the axial emission currents were measured under different voltage and pressure difference conditions with a CILET experimental system.The emission can be divided into two stable states and one unstable state based on the flow and current characteristics.The current in Stable state Ⅰ increases non-linearly with the voltage,while that in Stable state Ⅱ is nearly linear with respect to the voltage.The number of cones increases with the voltage in stable states,while the cones become short and crowded under high-voltage conditions.The variation law of the number of cones can be explained with the self-organization theory.The variation in the current exhibits a good correlation with the number of cones.This study demonstrates the feasibility of circular emitters and experimentally indicates that the emission current is improved by approximately two orders of magnitude compared to that of a single capillary.
基金support from the National Nature Science Foundation of China(Grant No.52273256).
文摘Exploring electrode materials with larger capacity,higher power density and longer cycle life was critical for developing advanced flexible lithium-ion batteries(LIBs).Herein,we used a controlled two-step method including electrospraying followed with calcination treatment by CVD furnace to design novel electrodes of Si/Si_(x)/C and Sn/C microrods array consisting of nanospheres on flexible carbon cloth substrate(denoted as Si/Si_(x)/C@CC,Sn/C@CC).Microrods composed of cumulated nanospheres(the diameter was approximately 120 nm)had a mean diameter of approximately 1.5μm and a length of around 4.0μm,distributing uniformly along the entire woven carbon fibers.Both of Si/Si/Si_(x)/C@CC and Sn/C@CC products were synthesized as binder-free anodes for Li-ion battery with the features of high reversible capacity and excellent cycling.Especially Si/Six/C electrode exhibited high specific capacity of about 1750 mA∙h∙g^(−1)at 0.5 A∙g^(−1)and excellent cycling ability even after 1050 cycles with a capacity of 1388 mA∙h∙g^(−1).Highly flexible Si/Si_(x)/C@CC//LiCoO_(2)batteries based on liquid and solid electrolytes were also fabricated,exhibiting high flexibility,excellent electrical stability and potential applications in flexible wearable electronics.
基金financially supported by the National Natural Science Foundation of China(Nos.22104112 and 22374110)the Fundamental Research Funds for the Central Universities。
文摘The investigation of reaction kinetics is the key to understanding the nature of reaction processes.However,monitoring fast photochemical reactions by mass spectrometry remains challenging.Herein,we developed an optical focusing inductive electrospray(OF-iESI)mass spectrometry platform for real-time and in-situ photoreaction monitoring.Coaxial irradiation from back of nanoelectrospray emitter with a taper section was utilized,so the emitter could act as optical lens to help achieving much larger optical power density at emitter tip compared to other sections,which allowed for in-situ reaction monitoring of photoreactions.Through theoretical calculations,the highest optical power density region volume was ca.45 nL.We also integrated a controller for the laser source(450 nm),enabling the modulation of pulse duration(>1 ms).This facilitates the study of photochemical reaction kinetics.The in-situ capability of this device was proved by capturing the short-lived photogenerated intermediates during the dehydrogenation of tetrahydroquinoline.This device was further used to investigate the kinetics of triplet energy transfer based Paternò-Büchi reaction.The reaction order has hitherto remained undetermined while the result of OF-iESI suggested it followed pseudo-second-order reaction kinetics.The short-lived donor-acceptor collision complex intermediate was also successfully identified by tandem mass spectrometry.
基金supported by the National Key R&D Program of China(No.2020YFC2201100)the National Natural Science Foundation of China(Nos.12175032,12102082,12275044,12402327,12405290 and 12211530449)+4 种基金the Joint Program of the Science and Technology Program of Liaoning,China(No.2023JH2/101700285)the Fundamental Research Funds for the Central Universities of China(Nos.DUT22RC(3)078,DUT23RC(3)040 and DUT24ZD106)the S&T Program of Hebei,China(No.246Z2301G)the S&T Innovation Program of Hebei,China(Nos.SJMYF2022X18 and SJMYF2022X06)the Beijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology and Advanced Space Propulsion Laboratory of BICE,China(No.LabASP-2023-07).
文摘The electrospray thruster supplied by ionic liquid is a promising micro-propulsion thruster with small size and precise thrust, which can emit both cations and anions to achieve self-neutralization. In order to further investigate the effect of ion solvation energy on the evaporation of cations and anions from ionic liquid under the action of a uniform electric field, this paper establishes a transient Electrohydrodynamic (EHD) model for free ionic liquid droplets undergoing ion evaporation. The dynamic processes of droplet deformation and ion evaporation are simulated. And the study further focuses on the influence of different ion solvation energies for cations on the droplet morphology and the ion evaporation characteristics at the positively charged end and negatively charged end of the droplet. The results indicate that, when the ion solvation energy for cations is higher than that of anions, it will cause the ion evaporation at the positively charged end of the droplet to lag behind the ion evaporation at the negatively charged end. And the higher the ion solvation energy for the cations, the longer the evaporation lag time at the positively charged end of the droplet, which will lead to a higher peak of surface charge density that can be reached, resulting in a larger evaporation current and sharper droplet stretching deformation. Additionally, the peak surface charge density of the positively charged end of the droplet is linearly related to the ion solvation energy for cations, while the peak surface charge density of the negatively charged end remains almost unchanged and is not significantly affected by the ion solvation energy for cations.
基金supported by Jiangxi Provincial International Science and Technology Cooperation Project(Nos.20203BDH80W010 and 20232BBH80012)the National Natural Science Foundation of China(Nos.82160410 and 81860379)+1 种基金Foundation of Jiangxi Provincial Department of Science and Technology(No.20212ACB206018)Key Research and Development Program of Jiangxi Province(No.20223BBG71009)。
文摘Accurate determination of lung cancer margins at the molecular level is of great significance to determine the optimal extent of resection during surgical operation and reduce the risk of postoperative recurrence.In this study,internal extractive electrospray ionization mass spectrometry(i EESI-MS)was used to trace potential molecular tumor margins in lung cancer tissue.Molecular differential model for the determination of lung cancer tumor margin was established via partial least-squares discriminant analysis(PLS-DA)of iEESI-MS data collected from lung tissue pieces within cancer tumor area and iEESI-MS data collected from lung tissue pieces outside cancer tumor area.Proof-of-concept data demonstrate that the developed molecular differential model yields ca.1-2 mm wider potential molecular tumor margin of a lung cancer compared to the conventional histological analysis,showing promising potential of iEESI-MS to increase the accuracy of tumor margins determination and lower risk of lung cancer postoperative recurrence.Furthermore,our results revealed that creatine and taurine showed positive correlations with lung cancer.
基金supports by the National Natural Science Foundation of China(No.22174037)the Joint Funds of the Hunan Provincial Natural Science Foundation of China(No.2023JJ50255)+1 种基金Changsha Science and Technology Project(No.Z202269490128)National Key Research and Development Program of China(No.2023YFF0613400)are appreciated.
文摘Traditional electrospray ionization tandem mass spectrometry(ESI-MS^(n))has been a powerful tool in diverse research areas,however,it faces great limitations in the study of protein-small molecule interactions.In this article,the state-of-the-art temperature-controlled electrospray ionization tandem mass spectrometry(TC-ESI-MS^(n))is applied to investigate interactions between ubiquitin and two flavonol molecules,respectively.The combination of collision-induced dissociation(CID)and MS solution-melting experiments facilitates the understanding of flavonol-protein interactions in a new dimension across varying temperature ranges.While structural changes of proteins disturbed by small molecules are unseen in ESI-MS^(n),TC-ESI-MS^(n)allows a simultaneous assessment of the stability of the complex in both gas and liquid phases under various temperature conditions,meanwhile investigating the impact on the protein’s structure and tracking changes in thermodynamic data,and the characteristics of structural intermediates.
基金financially supported by Jiangxi University of Chinese Medicine School-level Science and Technology Innovation Team Development Program(No.CXTD22005)PhD research startup fund of Jiangxi University of Chinese Medicine(No.2023BSZR005)。
文摘Selenium is one of the important trace elements in the human body.Its deficiency will directly affect human health.With people's attention to health,the content of selenium in food has gradually attracted attention.However,detecting selenium compounds in complex samples remains a challenge.In this work,we built an online heating-reaction device.This device combines the electrospray extraction ionization mass spectrometry(EESI-MS)with the heating reaction device,which can simultaneously detect various selenium compounds in complex liquid samples.Under acidic conditions,the sample was heated and catalyzed by a heating reaction device,so that the SeO~(2-)_(3)and O-phenylenediamine(OPD)could generate 1,3-dihydro-2,1,3-benzoselenadiazole.Based on the above reactions,we can detect organic selenium,inorganic selenium and other compounds in liquid samples by organic mass spectrometry.In this experiment,we determined the content of three forms of selenium:selenomethionine(SeMet),l-selenocystine(SeCys(2)),and sodium selenite.The calibration curves for SeMet,SeCys(2),and sodium selenite showed strong linearity within a range of 0.50-50.00μg/L.The limits of detection(LOD)for the three compounds were 0.22,0.27,and 0.41μg/L,respectively.The limits of quantification(LOQ)were 0.68,0.81,and 1.23μg/L,respectively.Spiked recoveries at three levels ranged from 98.8%to 106.1%.In addition,this method can simultaneously detect three selenium compounds and three other specific chemical components in tea infusion samples,providing a rapid and efficient method for identifying tea quality.
基金supported by Research and Development Program of Shaanxi Province,China(Grant No.2021ZDLGY10-09)the High-End Foreign Expert Recruitment Program,China(Grant No.G2023170009L)the Science and Technology on Electromechanical Dynamic Control Laboratory,China(Grant No.6142601220111)。
文摘To explore the feasibility of electrospray-based additive manufacturing for thin-film fabrication in zero-or microgravity environments,we conducted numerical simulations of charged droplet behavior under zero-gravity conditions,followed by ground-based experimental validation using an anti-gravity electrospray(AG-ES)strategy.First,simulations of charged droplet deposition during the electrospray process showed that the presence or absence of gravity did not significantly affect deposition behavior.Second,simulations of droplet-substrate collisions indicated that the presence of an electric field could reduce the risk of droplet splashing.Third,simulations of droplet coalescence under zero-gravity conditions demonstrated that an electric field could promote the coalescence of charged droplets.An AG-ES experimental platform featuring an inverted nozzle-substrate configuration was constructed on the ground.Comparative experiments using Rhodamine B solution and TiO_(2)nanoparticle dispersions were performed in both AG-ES and conventional electrospray(ES)modes.The results indicated that the spray cone angle,deposition area,and film morphology were comparable between the two modes.Finally,multilayer alternating-current electroluminescent(ACEL)devices were fabricated via AG-ES using ZnS:Cu/poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP),BaTiO_(3)/polyvinylpyrrolidone(PVP),and silver nanowire(AgNW)inks,achieving a maximum luminance of 66.2 cd/m^(2).This study demonstrates the potential of the electrospray process for functional thin-film fabrication under microgravity conditions.
基金supported by the National Key R&D Program of China(Nos.2020YFC2201103 and 2022YFB4601300)National Natural Science Foundation of China(No.U22B20120)+1 种基金the Program of Beijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology(No.LabASP-2024-09)the Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘The ionic liquid electrospray thruster is a microminiature thruster that can be applied on a micro or nano-satellite,and its highly energy-efficient,compact,modular system can be used for both main propulsion and altitude control.In this study,an ionic liquid electrospray thruster with a 100-tip emitter configuration is tested primarily to examine the difference in performance of the thruster at different angles with time-of-flight(TOF)mass spectrometry tests.In the experiment,it was measured that the half-angle of the thruster plume angle emission was in the range of−60 degrees to+65 degrees.Accordingly,the measurement range was set from−50 degrees to+50 degrees,with an interval of 10 degrees.Relative to the results of the 0 degree current curve,the positive mode is relatively homogeneous at all angles of the operating mode.In the negative mode,for n 2 ions,the negative angle region accounts for a larger proportion and the positive angle region accounts for a smaller proportion,which makes a significant difference to the specific impulse of the two regions.The range of the specific impulse at different angles is 3776-4401 s under the typical working condition of+2.5 kV.Under−2.5 kV,the range of the specific impulse at different angles is 3309-4654 s.This research quantifies the angular performance variations of the ionic liquid electrospray thruster,offering valuable data to improve its design and operational reliability for precise propulsion and altitude control in satellite applications.
文摘The ginkgo terpenoids including bilobalide and ginkgolides are the main pharmaceutical components in the leaves or extracts of Ginkgo biloba L. In this paper, the analysis of bilobalide and ginkgolides in leaves of Ginkgo biloba L. by high performance liquid chromatography (HPLC)-electrospray ionization (ESI)-mass spectrometry (MS) was carried out. The separation was performed on Inertsil ODS3 column with methanol-water (36:64) as mobile phase, with 1 mL·min -1 of flow rate at 35℃. Then the mass spectrum analysis was conducted by ZMD micromass electrospray ionization (ESI)-mass spectrometer (MS). The HPLC total ion chromatogram and selected ion chromatogram (with 325, 407, 423, 439 of m/z) of the sample and ESI-/MS mass spectra of the peaks in the chromatograms were obtained. So bilobalide, ginkgolide A, B, C and J in Ginkgo biloba L. leaves were identified. The method is easy and rapid, with a good accuracy.
文摘An ionic liquid(IL)electrospray thruster was developed for application in micro-nano satellites or gravitational wave detectors.The thruster employed a porous ceramic emitter with seven emitter strips located on its emission surface.Without any liquid-supply device,IL was delivered through porous media to emitter strips via capillary effect.Multiple emission sites then formed at the tip of each strip.A charged beam of up to 350μA(with a current density of 540μA cm^(-2))was stably produced in the negative mode.However,in the positive mode,a corona was observed which could prevent the thruster from emitting larger current.A time-of-flight mass spectrometer with significantly improved signal-to-noise ratio was built,which was used to obtain the mass distribution of the beam of the thruster.A retarding potential analysis was also performed.The test results showed that the thruster worked in the pure-ion regime,and delivered a maximum thrust of 67.1μN with specific impulses of 3952 s and 3117 s in the positive and negative modes,respectively.
基金supported by the National Key R&D Program of China(No.2020YFC2201103).
文摘In order to meet the demand of CubeSats for low power and high-performance micro-propulsion system,a porous ionic liquid electrospray thruster prototype is developed in this study.1010 conical emitter arrays are fabricated on an area of 3.24 cm^(2) by computer numerical control machining technology.The propellant is 1-ethyl-3-methylimidazolium tetrafluoroborate.The over-all dimension of the assembled prototype is 3 cm×3 cm×1 cm,with a total weight of about 15 g(with propellant).The performance of this prototype is tested under vacuum.The results show that it can work in the voltage range of±2.0 kV to±3.0 kV,and the maximum emission current and input power are about 355 lA and 1.12 W.Time of Flight(TOF)mass spectrometry results show that cationic monomers and dimers dominate the beam in positive mode,while a higher proportion of higher-order solvated ion clusters in negative mode.The maximum specific impulse is 2992 s in positive mode and 849 s in negative mode.The thrust is measured in two methods:one is calculated by TOF results and the other is directly measured by high-precision torsional thrust stand.The thrust(T)obtained by these two methods conforms to a certain scaling law with respect to the emis-sion current(I_(em))and the applied voltage(V_(app)),following the scale of T-Iem_(Vapp)^(0.5),and the thrust range is from 2.1 lN to 42.6 lN.Many thruster performance parameters are significantly different in positive and negative modes.We speculate that due to the higher solvation energy of the anion,more solvated ion clusters are formed rather than pure ions under the same electric field.It may help to improve thruster performance if porous materials with smaller pore sizes are used as reservoirs.Although there are still many problems,most of the performance parameters of ILET-3 are good,which can theoretically meet the requirements of CubeSats for micro-propulsion system.
基金co-supported by NSAF,China(No.U1730134)the National Natural Science Foundation of China(No.11772310)+1 种基金the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX202034)the Innovation and Entrepreneurship Fund of the Student Affairs Department of Northwestern Polytechnical University,China(No.2021-CXCY-005)。
文摘As a novel micro-propulsion system for small satellites(from micro to nano),the ionic liquid electro spray propulsion system is a promising candidate.However,performance measurement and evaluation of the Ionic Liquid Electrospray Thruster(ILET)is one of the most challenging issues for practical application,due to the difficulties in the development of a prototype and direct measurements of micro-thrust and small flow rate.To address this issue,a Modular Ionic Liquid Electrospray Thruster(MILET)prototype is constructed,and a diagnostic system for thrust and mass flow rate is specially developed based on an analytical balance method.With the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as the propellant,a series of experiments is carried out on the MILET prototype under a wide operating condition through changing the applied voltage to control the thrust.Under different applied voltages,the thrust and the mass flow rate of the propellant are directly measured.The propulsive performance parameters of the thruster,such as thrust,specific impulse,thrust-to-power ratio,thruster efficiency,etc.,are comprehensively analyzed.Then,a performance comparison is made between the MILET and other representative ILETs.With a relatively low applied voltage ranging from 1550 V to 2000 V,the MILET achieves a quasi-constant specific impulse of 1263 s with the averaged thrust-to-power ratio of 65.2μN/W and thruster efficiency of 40.7%.The performance of ILET is also compared with other typical electric propulsions.The results demonstrate that the ILET exhibits an excellent ability of minimalization with high specific impulse and thruster efficiency,which guarantees a great superiority in micro propulsions.Finally,the ways to further improve the performance of ILET are discussed,which further confirms the potential prospect of ILET.The present result helps to advance the development and application of ILET.
基金supported by the National Instrumentation Program (No. 2016YFF0100304)the National Natural Science Foundation of China(Nos. 21335007, 81773678)+1 种基金the CAMS Innovation Fund for Medical Sciences(No. 2016-12 M-1-009)PUMC Youth Fund and the Fundamental Research Funds for the Central Universities(No. 3332015177)
文摘Mass spectrometry imaging (MSI) technology can simultaneously obtain the spatial distribution of thousands of chemical compounds and has unique advantages compared to other techniques that allow mapping the surface of bio-tissue. Here, we combined an air flow-assisted desorption electrospray ionization (AFADESI) MSI device with a high-resolution mass spectrometer to optimize the system parameters and achieve more accurate spatial distribution characteristics for compounds of interest while investigating bio-tissue sections. The platform set-up, required instrumentation, sample pretreatment, parameter optimization and bio-tissue characterization are described and discussed.Finally, the parameter conditions that can provide optimal ionic intensity and enhanced resolution were confirmed. The reasonable resolution and sensitivity improvements of AFADESI-MSI have been achieved through tandem a high-resolution mass spectrometer system, therefore, it would be a promising technique for the bio-tissue imaging analysis.
基金supported by the 90th Anniversary of Chulalongkorn University,Rachadapisek Sompote Fund,Chulalongkorn University,through the Nanotec–CU Center of Excellence on Food and AgricultureInternational Program in Hazardous Substance, and Environmental Management Center of Excellence on Hazardous Substance Management(HSM)Chulalongkorn University
文摘In present study, a simultaneous electrospinning and electrospraying（SEE） process was employed to produce microclusters of TiO2 nanoparticles and interlock them in nanofibrous network. The photocatalytic composite membranes（PCMs） were fabricated by electrospraying TiO2 nanoparticle suspension into microcluster form that dispersed and entrapped within nylon-6 electrospun fiber membrane. Three PCMs membrane with TiO2 content of 52.0, 83.6,and 91.7 wt.% were successfully fabricated. The membrane consisted of TiO2 microclusters,ranging in sizes from around 0.3 to 10 μm, distributed uniformly within the nylon-6 nanofibrous network. PCMs photocatalytic activity against Methylene Blue（MB） in aqueous solution showed more than 98% MB removal efficiency after 120 min of photocatalytic oxidation（PCO） for all PCMs. For PCM with the highest TiO2 content tested for 5 PCO cycles, it was found that most of their TiO2 content remained incorporated within the nanofibrous structure. The concept of nanoparticles clusters entrapment with SEE fabrication employed here provide a simple and effective method for reducing detachment of nanostructure phase from nanocomposite membrane.
文摘Electrospray ionization mass spectrometry（ESI-MS） was applied simultaneously in determining norditerpenoid alkaloids from the roots of Aconitum sinomantanum Nakai （RAS） based on molecular mass information. The tandem mass spectra（ ESI-MS^n） provided the alkaloidal structural information, through which the existence of these alkaloids was further confirmed. Accordingly, six known norditerpenoid alkaloids were simultaneously determined on the basis of their ESI-MS^n spectra. Furthermore, based on the diagnostic fragmentation pathways of alkaloidal MS^n, a rapid method for direct detection and characterization of alkaloids from an ethanolic extract of RAS was described.
基金financially supported by the National Natural Science Foundation of China(No.51903090)the Science and Technology Program of Guangzhou(No.202102020632)Fundamental Research Funds for the Central Universities(No.2020ZYGXZR046)。
文摘The high-efficiency fabrication of high-quality microcapsules containing epoxy is crucial to the further development of the potential practical self-healing epoxy systems based on microencapsulated two-part epoxy-amine chemistry.Herein,a novel microencapsulation technique based on non-equilibrium droplets via integrating electrospraying and interfacial polymerization(ES-IP)was established to efficiently microencapsulate epoxy monomers.The ES-IP technique,consisting of three continuous steps,i.e.electrospraying to massively generate droplets,enwrapping every single droplet through instant interfacial polymerization,and thickening shell at an elevated temperature,has great flexibility to regulate the microencapsulation process and the microcapsule quality.The fabricated core-shell structured epoxy microcapsules(Ep-MCs)were comprehensively characterized for their properties,showing that they have high cleanness with rare impurities,controllable and tunable size,good thermal stability and tightness,and high effective core fraction.The high-quality Ep-MCs were adopted to formulate a self-healing epoxy based on the microencapsulated epoxy-amine chemistry.The highest healing efficiency,in terms of the recovered mode I fracture toughness,of 110±17%was achieved after being healed at room temperature(~25℃)for 48 h.While the developed ES-IP technique facilitates the microencapsulation technique based on non-equilibrium droplets,the fabricated high-quality Ep-MCs greatly promote the further developments of the practical self-healing materials.
文摘The electrospray thruster is becoming popular in space propulsion due to its low power and high specific impulse.Before this work,an electrospray thruster based on a porous emitter was developed.In order to achieve larger and more stable thrust,the thruster was redesigned,and the influence of the space between strips on thrust was studied.Four types of emitter were tested,and they had 1,3,4 and 14 emitter-strips on the emission surface of the same size respectively.According to the experimental results,the maximum extraction voltage and emission current of the four thrusters are different under stable operational conditions.The measured stable emission currents and extraction voltages were-500μA/-5000 V,-1570μA/-3800 V,-1200μA/-3800 V,and-650μA/-4500 V,respectively.Increasing the number of strips may not result in the emission current increasing,but changing the stable operational range of the emission current per strip and the extraction voltage.The maximum stable operational extraction voltages of 3 and 4 emitter-strips are lower than those of 1 and 14 emitter-strips,but the emission currents are higher than those of 1 and 14 emitter-strips.Time-of-flight mass spectrometry was used to analyze the mass distribution and obtain the performance of the thruster in the case of thrusters with 1 and 3 emitter-strips.Both of their plumes were composed of very small ion cluster(the pure-ion regime),and their thrusts were 80.1μN,219.2μN with specific impulses of 5774 s,5047 s,respectively.
文摘A study was conducted regarding the effect of concentration of poly (vinylidene fluoride) (PVDF)/N,N-dimethylformamide (DMF) and PVDF/DMF/acetone solutions on the transition between electrospray and electrospinning and on the formation of the ? and ? crystalline phases of PVDF. The crystalline phases present in the samples, crystallinity and morphology were determined by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. Low concentration solutions resulted in films consisting of small droplets (electrospray) containing predominantly the ? phase. High concentration solutions resulted in a non-woven mesh of nano-to-micron diameter fibers (electrospinning) containing exclusively the ? phase. These results showed that, the formation of this phase in the electrospinning is related mainly to the solvent evaporation rate, and not to drawing experienced by the polymer during the process. Solvent type affected the amount of crystalline phase present, the boundary concentration between the two processes and the average diameter of fibers. Meshes processed by electrospinning display a degree of crystallinity higher than the films obtained by electrospray.
基金the Danish Council for Inde-pendent Research(Grant No.DFF-12-131927)for financial sup-port of this project
文摘Hypromellose acetate succinate(HPMCAS) microparticles containing the poorly-water soluble drug celecoxib(CEL) were prepared by electrospraying intended for oral drug delivery. Various solvent mixtures with different solubility for CEL and HPMCAS were used to induce changes in the polymer structural conformation of the microparticles. The performance of the prepared microparticles was evaluated by studying the solid state from, particle size and morphology, radial drug distribution and drug release. CEL was amorphous in all electrosprayed HPMCAS microparticles. The particle size and morphology was dependent on the solubility of HPMCAS in the solvent mixture used with poorer solvents resulting in smaller microparticles with rougher appearance. The CEL distribution on the particles surface was relatively homogeneous and similar for all microparticles. Drug release from the microparticles was observed at a higher rate depending on the solubility of HPMCAS in the solvent used for electrospraying, and in all cases an at least 4-fold higher rate was observed compared with the crystalline drug. Drug precipitation from the supersaturated solution was inhibited by HPMCAS for all microparticles based on its parachute effect while crystalline CEL did not reach supersaturation. This study demonstrated that electrospraying can be used to produce microparticles with tailored properties for pharmaceutical application by adjusting solvent selection.
