Chlorine dioxide （OC10） is an important indicator for Cl-activation. The monitoring of OC10 appears to be crucial for understanding the chemistry of Cl-initialed oxidation and its impact on air quality in polluted c...Chlorine dioxide （OC10） is an important indicator for Cl-activation. The monitoring of OC10 appears to be crucial for understanding the chemistry of Cl-initialed oxidation and its impact on air quality in polluted coastal regions and industrialized areas. We report the development of a Xe arc lamp based near-ultraviolet （335-375 nm） incoherent broad- band cavity enhanced absorption spectroscopy （IBBCEAS） spectrometer for quantitative assessment of OC10 in an atmospheric simulation chamber. The important intermediate compound CH20, and other key atmospheric trace species （NO2） were also simultaneously measured. The instrumental performance shows a strong potential of this kind of IBBCEAS instrument for field and laboratory studies of atmospheric halogen chemistry.展开更多
Infrared(IR)spectroscopy,a technique within the realm of molecular vibrational spectroscopy,furnishes distinctive chemical signatures pivotal for both structural analysis and compound identification.A notable challeng...Infrared(IR)spectroscopy,a technique within the realm of molecular vibrational spectroscopy,furnishes distinctive chemical signatures pivotal for both structural analysis and compound identification.A notable challenge emerges from the misalignment between the mid-IR light wavelength range and molecular dimensions,culminating in a constrained absorption cross-section and diminished vibrational absorption coefficients(Supplementary data).展开更多
Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency （RF） ma...Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency （RF） magnetron sputtering. The boron nitride thin films are characterized by Fourier transform infrared spectra. The average particle diameters of silver nanoparticle thin films are 126.6, 78.4, and 178.8 nm. The results show that the sizes of the silver nanoparticles have effects on the intensities of infrared spectra of boron nitride thin films. An enhanced infrared absorption is detected for boron nitride thin film grown on silver nanoparticle thin film. This result is helpful to study the growth mechanism of boron nitride thin film.展开更多
In order to study the effects of nanoparticles on the CO_2 absorption in ammonia,nanofluids with different ammonia concentration and different nanoparticle solid loading were prepared by a two-step method.The nanoflui...In order to study the effects of nanoparticles on the CO_2 absorption in ammonia,nanofluids with different ammonia concentration and different nanoparticle solid loading were prepared by a two-step method.The nanofluids-enhanced gas absorption test devices were also established. The CO_2 absorption in TiO_2,CuO,SiO_2 nanofluids,which nanoparticles solid loading were 1. 0-8. 0 g/L,was tested respectively. In comparison with the blank absorption experiment,the effects of nanoparticle solid loading,nanoparticle types,ammonia concentration on the removal efficiency and removal rate were obtained. Experimental results show that adding nanoparticles can enhance the removal efficiency and removal rate,which increase first and then decrease with the increase of nanoparticle solid loading,and there exists an optimum solid loading of TiO_2 nanoparticles. The effect of SiO_2 nanofluid is inhibitory on the reaction. The enhancement factor of CuO nanofluid is always hovering around 1,which does not show the obvious enhancement or inhibition on the reaction. The optimum solid loading decreases gradually with the increase of ammonia concentration. In addition,according to the experimental results,the mechanism of enhanced absorption was analyzed theoretically.展开更多
Direct-comb spectroscopy techniques uses optical frequency combs(OFCs)as spectroscopic light source.They deliver high sensitivity,high frequency resolution and precision in a broad spectral range.Due to these features...Direct-comb spectroscopy techniques uses optical frequency combs(OFCs)as spectroscopic light source.They deliver high sensitivity,high frequency resolution and precision in a broad spectral range.Due to these features,the field has burgeoned in recent years.In this work we constructed an OFC-based cavity-enhanced Fourier-transform spectrometer in the nearinfrared region and used it for a line-shape study of rovibrational transitions of CO perturbed by Ar.The highly sensitive measurements spanned the wavenumber range from 6270 cm^-1 to 6410 cm^-1,which covered both P and R branch of the second overtone band of CO.The spectrometer delivers high-resolution surpassing the Fourier-transform resolution limit determined by interferogram length,successfully removing ringing and broadening effects caused by instrumental line shape function.The instrumental-line-shape-free method and high signal-to-noise ratio in the measurement allowed us to observe collisional effects beyond those described by the Voigt profile.We retrieved collisional line-shape parameters by fitting the speed-dependent Voigt profile and found good agreement with the values given by precise cavity ring-down spectroscopy measurements that used a continuous-wave laser referenced to a stabilized OFC.The results demonstrate that OFC-based cavity-enhanced Fouriertransform spectroscopy is a strong tool for accurate line-shape studies that will be crucial for future spectral databases.展开更多
The influence of nano-particles on CO2 absorption was studied experimentally in a stirred thermostatic reactor. Nano-A1203 and carbon nanotube （CNT） particles which showed different hydrophobic properties were chose...The influence of nano-particles on CO2 absorption was studied experimentally in a stirred thermostatic reactor. Nano-A1203 and carbon nanotube （CNT） particles which showed different hydrophobic properties were chosen for the investigation. The experimental results were compared with that of micron-size activated carbon （AC） and Al2O3 particles. From the results, no enhancement by micron-size A1203 was found, and with the increase of A1203 concentration, the enhancement factor decreased. However, nano-Al203 showed a weak enlaancement tor me COz absorption. AC and CNT particles all intensified the gas-liquid mass transfer effectively, yet the trend of the enhancement factor with stirring speed for the two particles was different. With increasing stirring speed, the enhancement factor of AC particles was decreased, wl＇iereas in CNT suspensions it was increased. The experimental phenomena demonstrated a difference in enhancement mechanism for different size particles. For nano-particles, besides the influence of adsorbability and hydrophobicity, the micro-convection caused by Brownian motion should be also taken into account. Considering the micro-convection effect, a theoretical model was developed to shed light on the absorption enhancement bv nano-oarticles.展开更多
Two methods of the modification of zeolite were employed： framework element modification and surface coating, and the influence of the zeolites before and after modification on the CO2 absorption was investigated. It...Two methods of the modification of zeolite were employed： framework element modification and surface coating, and the influence of the zeolites before and after modification on the CO2 absorption was investigated. It was found that although hydrophobicity of zeolite could be obtained by means of the surficial organic coating in the method of surface coating _mod!fication, partial channel of zeolite would be plugged, as a result, leading to the surface area reducing greatly. Distinctively, the framework element modification method could maintain not only complete lattice structure and adsorption capability of zeolite, but would also obtain a good hydrophobic property. Consequently, significant enhancement on gas absorption by this modified zeolite was achieved and up to a maximum enhancement factor of 2.62. This shows that the solid particles with good enhancement role to gas absorption need not only good adsorptive capability but also certain hydrophobicity. An unsteady heterogeneous model was employed to predict enhancement factor and the calculated results agree well with the experimental data.展开更多
This study investigates seasonal variations of mass absorption efficiency of elemental carbon(MAE_(EC))and possible influencing factors in urban Guangzhou of South China.Mass concentrations of elemental carbon(EC)and ...This study investigates seasonal variations of mass absorption efficiency of elemental carbon(MAE_(EC))and possible influencing factors in urban Guangzhou of South China.Mass concentrations of elemental carbon(EC)and organic carbon(OC)in PM_(2.5) and aerosol absorption coefficient(b_(ap))at multi-wavelengths were simultaneously measured in four seasons of 2018-2019 at hourly resolution by a semi-continuous carbon analyzer and an aethalometer.Seasonal average mass concentrations of EC were in the range of 1.36-1.70μgC/m^(3) with a lower value in summer than in the other seasons,while those of OC were in the range of 4.70–6.49μgC/m^(3) with the lowest value in summer and the highest in autumn.Vehicle exhaust from local traffic was identified to be the predominant source of carbonaceous aerosols.The average aerosol absorption Angstrom exponents(AAE)were lower than 1.2 in four seasons,indicating EC and b_(ap) were closely related with vehicle exhaust.Seasonal MAE EC at 550 nm was 11.0,8.5,10.4 and 11.3 m^(2)/g in spring,summer,autumn,and winter,respectively.High MAE EC was related with the high mass ratio of non-carbonaceous aerosols to EC and high ambient relative humidity.展开更多
To increase the absorption in a thin layer of absorbing material （amorphous silicon, a-Si）, a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enha...To increase the absorption in a thin layer of absorbing material （amorphous silicon, a-Si）, a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic （TM）-polarized light, but also for transverse electric （TE）-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.展开更多
We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter sca...We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter scale meso-slit matrix. Theoretical and numerical results reveal that this exotic phenomenon is attributed to the noticeable velocity and temperature gradients induced at the junctures of the micro- and meso-slits, which cause significant loss of sound energy as a result of viscous and thermal effects. It is demonstrated that the proposed thin multi-slit hybrid structure with micro-scale configuration is capable of controling low frequency noise with large wavelength, which is attractive for applications where the size and weight of a sound absorber are restricted.展开更多
Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole...Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole approximation （DDA）,we study the absorption and scattering properties of two-dimensional square silver nanodisks （2D SSN） arrays on the single crystal silicon solar cell.Based on the effective reflective index model of the single crystal silicon solar cell,we investigate the optical enhancement absorption of light energy by varying the light incident direction,particle size,aspect ratio,and interparticle spacing of the silver nanodisks.The peak values and position of the optical extinction spectra of the 2D square arrays of noble metal nanodisks are obtained with the different array structures.展开更多
An insulin-loaded emulsion system （IES） was developed as a hypoglycaemic drug for transmucosal delivery. The selected formulation was a stable oil/water emulsion system. The particles in the emulsion system were dis...An insulin-loaded emulsion system （IES） was developed as a hypoglycaemic drug for transmucosal delivery. The selected formulation was a stable oil/water emulsion system. The particles in the emulsion system were distributed evenly, and the particle size ranged from 20 to 260 nm（ average size ： 67.5 nm ）. Soybean lecithin played an important role in the emulsion system due to its abilities of acting as both absorption enhancer for insulin uptake through sublingual mucosa and oily phase for the emulsion system. The laser confocal scanning microscopic（LCSM） study showed that FITC-labelled insulin could penetrate the sublingual mucosa of rabbits, and the phase diagrams of the emulsion system suggested that soybean lecithin could take the place of oily phase to construct a stable emulsion system even if the traditional oil was absent. The applications of soybean lecithin as pharmaceutical biomaterial were extended for the further usage by present studies.展开更多
The broadband absorption enhancement effect in ultrathin molybdenum disulfide(Mo S2)films is investigated.It is achieved by inserting the Mo S2 film between a dielectric film and a one-dimensional silver grating backe...The broadband absorption enhancement effect in ultrathin molybdenum disulfide(Mo S2)films is investigated.It is achieved by inserting the Mo S2 film between a dielectric film and a one-dimensional silver grating backed with a silver mirror.The broadband absorption enhancement in the visible region is achieved,which exhibits large integrated absorption and short-circuit current density for solar energy under normal incidence.The optical properties of the proposed absorber are found to be superior to those of a reference planar structure,which makes the proposed structure advantageous for practical photovoltaic application.Moreover,the integrated absorption and short-circuit current density can be maintained high for a wide range of incident angles.A qualitative understanding of such broadband absorption enhancement effect is examined by illustrating the electromagnetic field distribution at some selected wavelengths.The results pave the way for developing high-performance optoelectronic devices,such as solar cells,photodetectors,and modulators.展开更多
We extend the third perturbation theory to study the polarization control behavior of the intermediate state absorption in Nd^（3＋）ions. The results show that coherent interference can occur between the single-photo...We extend the third perturbation theory to study the polarization control behavior of the intermediate state absorption in Nd^（3＋）ions. The results show that coherent interference can occur between the single-photon and three-photon excitation pathways, and depends on the central frequency of the femtosecond laser field. Moreover,single-photon and three-photon absorptions have different polarization control efficiencies, and the relative weight of three-photon absorption in the whole excitation processes can increase with increasing the laser intensity.Therefore, the enhancement or suppression of the intermediate state absorption can be realized and manipulated by properly designing the intensity and central frequency of the polarization modulated femtosecond laser field.This research can not only enrich theoretical research methods for the up-conversion luminescence manipulation of rare-earth ions, but also can provide a clear physical picture for understanding and controlling multi-photon absorption in a multiple energy level system.展开更多
The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control...The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited （TL）-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.展开更多
Titanium-doped sapphire is an excellent laser crystal which has a bright future.But the residual infrared absorption in laser operation region of the crystal hindered the enhancement of the laser gain.Reducing the res...Titanium-doped sapphire is an excellent laser crystal which has a bright future.But the residual infrared absorption in laser operation region of the crystal hindered the enhancement of the laser gain.Reducing the residual infrared absorption is the key to that the crystal goes from experimental prototypesto commercially available products.展开更多
Different kinds of hetero-structured ZnO/nanoporous carbon(NPC)composites with enhanced microwave absorption properties have been designed through a self-templated route by using zeolitic imidazolate framework(ZIF-8)a...Different kinds of hetero-structured ZnO/nanoporous carbon(NPC)composites with enhanced microwave absorption properties have been designed through a self-templated route by using zeolitic imidazolate framework(ZIF-8)as raw material.Thus,a series of samples with different dielectric features were obtained via calcination processes.Interestingly,the annealing temperatures during the carbonization procedures play a key role in the impedance matching and the dielectric relaxations for the final products composed of ZnO,NPC and nanopores.The heating temperatures could influence the degree of graphitization and the dielectric features.As a result,a maximum reflection loss of−25 dB with 1.55 mm can be achieved.In a word,this study confirms that the heating temperatures have important influences on dielectric as well as impedance matching for metal–organic frameworks,which is expected to be expanded to the design of many other efficient microwave absorbing materials.展开更多
In this work,we design oxygen vacancy-rich BiOBr:Yb^(3+)/Er^(3+)(BYE-OV)ultrathin nanosheets,which can effectively enhance UC luminescence by oxygen vacancy engineering.Density functional theory calculations and UV-Vi...In this work,we design oxygen vacancy-rich BiOBr:Yb^(3+)/Er^(3+)(BYE-OV)ultrathin nanosheets,which can effectively enhance UC luminescence by oxygen vacancy engineering.Density functional theory calculations and UV-Vis-NIR absorption spectra reveal that the existence of oxygen vacancies leads to the formation of an intermediate band(IB)in the bandgap,which can enhance the light absorption ability and promote electron excitation and bandgap transitions(VB→CB,VB→IB and IB→CB),thereby providing the transfer of abundant electrons from the host to Er^(3+)ions.As a result,the emission intensity of green and red is exceptionally enhanced by 6.5 and 12 times respectively via introduced oxygen vacancies.Meanwhile,BYE-OV exhibits superior photocatalytic activity for the degradation of RhB under visible-NIR light irradiation.The enhanced activity can be mainly ascribed to enhanced photoabsorption in the visible-NIR region and improved UC luminescence.This work offers a new strategy for a rational design for enhancing UC luminescence,which has potential for applications in visible-NIR light photocatalysis.展开更多
Magnetic carbon-based composites are the most attractive candidates for electromagnetic(EM)absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magne...Magnetic carbon-based composites are the most attractive candidates for electromagnetic(EM)absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magnetic branches.Metal-organic frameworks(MOFs)have demonstrated their great potential as sacrificing precursors of magnetic metals/carbon composites,because they provide a good platform to achieve high dispersion of magnetic nanoparticles in carbon matrix.Nevertheless,the chemical composition and microstructure of these composites are always highly dependent on their precursors and cannot promise an optimal EM state favorable for EM absorption,which more or less discount the superiority of MOFs-derived strategy.It is hence of great importance to develop some accompanied methods that can regulate EM properties of MOFs-derived magnetic carbon-based composites e ectively.This review comprehensively introduces recent advancements on EM absorption enhancement in MOFs-derived magnetic carbon-based composites and some available strategies therein.In addition,some challenges and prospects are also proposed to indicate the pending issues on performance breakthrough and mechanism exploration in the related field.展开更多
Efficient oral delivery of drugs treating brain diseases has long been a challenging topic faced by the drug delivery community. Fortunately, polyester nanoparticles offer certain solutions to this problem. This revie...Efficient oral delivery of drugs treating brain diseases has long been a challenging topic faced by the drug delivery community. Fortunately, polyester nanoparticles offer certain solutions to this problem. This review article firstly describes the main obstacles faced by oral administered brain targeting, including:(1)instability in the gastrointestinal tract;(2) poor penetration of the intestinal mucosa and epithelium;(3)blood clearance;and(4) restriction by the BBB. Then the key factors influencing brain-targeting efficiency of orally administered polyester nanoparticles are also discussed, such as size, shape and surface properties. Finally, recent brain-targeting delivery strategies using oral polyester nanoparticles as carriers and their effects on brain drugs transport are reviewed, and the delivery ‘as a whole’ strategy of polyester nanoparticles will provide new insight for oral brain-targeting delivery. And by combination of multiple strategies, both the stability and permeability of polyester nanoparticles can be greatly improved for oral brain drug delivery.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.41005017）, the Instrument Developing Project of the Chinese Academy of Sciences （No.YZ201121）, Jiangsu Provincial Natural Science Foundation of China （No.BK2011829）, and the Open Research Fund of Key Laboratory of Atmospheric Composition and Optical Radiation. The support of the Groupement de Recherche International SAMIA between CNRS （National Center for Scientific Research, France）, RFBR （Russian Foundation for Basic Research, Russia）, and CAS （Chinese Academy of Sciences, China） is acknowledged. We thank Dr. Albert A. Ruth at university college cork for the helpful discussion on the Xe lamp source based IBBCEAS.
文摘Chlorine dioxide （OC10） is an important indicator for Cl-activation. The monitoring of OC10 appears to be crucial for understanding the chemistry of Cl-initialed oxidation and its impact on air quality in polluted coastal regions and industrialized areas. We report the development of a Xe arc lamp based near-ultraviolet （335-375 nm） incoherent broad- band cavity enhanced absorption spectroscopy （IBBCEAS） spectrometer for quantitative assessment of OC10 in an atmospheric simulation chamber. The important intermediate compound CH20, and other key atmospheric trace species （NO2） were also simultaneously measured. The instrumental performance shows a strong potential of this kind of IBBCEAS instrument for field and laboratory studies of atmospheric halogen chemistry.
基金supported by National Natural Science Foundation of China(Grant No.:32301161)the Natural Scientific Foundation of Hunan Province,China(Grant No.:2023JJ60052)+3 种基金the Scientific Research Project of Hunan Provincial Health Commission,China(Grant No.:202112062218,20190161)the Scientific Research Project of Hunan Provincial Department of Education,China(Grant No.:22B0455)the Clinical“4310”Project of the University of South China,China(Grant No.:20224310NHYCG02)the Doctoral Scientific Research Foundation of University of South China,China(Grant No.:200XQD042).
文摘Infrared(IR)spectroscopy,a technique within the realm of molecular vibrational spectroscopy,furnishes distinctive chemical signatures pivotal for both structural analysis and compound identification.A notable challenge emerges from the misalignment between the mid-IR light wavelength range and molecular dimensions,culminating in a constrained absorption cross-section and diminished vibrational absorption coefficients(Supplementary data).
基金Project supported by the Natural Science Foundation of Beijing,China(Grant No.4072007)the National Natural Science Foundation of China(Grant Nos.60876006 and 60376007)
文摘Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency （RF） magnetron sputtering. The boron nitride thin films are characterized by Fourier transform infrared spectra. The average particle diameters of silver nanoparticle thin films are 126.6, 78.4, and 178.8 nm. The results show that the sizes of the silver nanoparticles have effects on the intensities of infrared spectra of boron nitride thin films. An enhanced infrared absorption is detected for boron nitride thin film grown on silver nanoparticle thin film. This result is helpful to study the growth mechanism of boron nitride thin film.
基金Sponsored by the Hebei Natural Science Foundation of Hebei Province of China(Grant No.B2014502056)
文摘In order to study the effects of nanoparticles on the CO_2 absorption in ammonia,nanofluids with different ammonia concentration and different nanoparticle solid loading were prepared by a two-step method.The nanofluids-enhanced gas absorption test devices were also established. The CO_2 absorption in TiO_2,CuO,SiO_2 nanofluids,which nanoparticles solid loading were 1. 0-8. 0 g/L,was tested respectively. In comparison with the blank absorption experiment,the effects of nanoparticle solid loading,nanoparticle types,ammonia concentration on the removal efficiency and removal rate were obtained. Experimental results show that adding nanoparticles can enhance the removal efficiency and removal rate,which increase first and then decrease with the increase of nanoparticle solid loading,and there exists an optimum solid loading of TiO_2 nanoparticles. The effect of SiO_2 nanofluid is inhibitory on the reaction. The enhancement factor of CuO nanofluid is always hovering around 1,which does not show the obvious enhancement or inhibition on the reaction. The optimum solid loading decreases gradually with the increase of ammonia concentration. In addition,according to the experimental results,the mechanism of enhanced absorption was analyzed theoretically.
文摘Direct-comb spectroscopy techniques uses optical frequency combs(OFCs)as spectroscopic light source.They deliver high sensitivity,high frequency resolution and precision in a broad spectral range.Due to these features,the field has burgeoned in recent years.In this work we constructed an OFC-based cavity-enhanced Fourier-transform spectrometer in the nearinfrared region and used it for a line-shape study of rovibrational transitions of CO perturbed by Ar.The highly sensitive measurements spanned the wavenumber range from 6270 cm^-1 to 6410 cm^-1,which covered both P and R branch of the second overtone band of CO.The spectrometer delivers high-resolution surpassing the Fourier-transform resolution limit determined by interferogram length,successfully removing ringing and broadening effects caused by instrumental line shape function.The instrumental-line-shape-free method and high signal-to-noise ratio in the measurement allowed us to observe collisional effects beyond those described by the Voigt profile.We retrieved collisional line-shape parameters by fitting the speed-dependent Voigt profile and found good agreement with the values given by precise cavity ring-down spectroscopy measurements that used a continuous-wave laser referenced to a stabilized OFC.The results demonstrate that OFC-based cavity-enhanced Fouriertransform spectroscopy is a strong tool for accurate line-shape studies that will be crucial for future spectral databases.
文摘The influence of nano-particles on CO2 absorption was studied experimentally in a stirred thermostatic reactor. Nano-A1203 and carbon nanotube （CNT） particles which showed different hydrophobic properties were chosen for the investigation. The experimental results were compared with that of micron-size activated carbon （AC） and Al2O3 particles. From the results, no enhancement by micron-size A1203 was found, and with the increase of A1203 concentration, the enhancement factor decreased. However, nano-Al203 showed a weak enlaancement tor me COz absorption. AC and CNT particles all intensified the gas-liquid mass transfer effectively, yet the trend of the enhancement factor with stirring speed for the two particles was different. With increasing stirring speed, the enhancement factor of AC particles was decreased, wl＇iereas in CNT suspensions it was increased. The experimental phenomena demonstrated a difference in enhancement mechanism for different size particles. For nano-particles, besides the influence of adsorbability and hydrophobicity, the micro-convection caused by Brownian motion should be also taken into account. Considering the micro-convection effect, a theoretical model was developed to shed light on the absorption enhancement bv nano-oarticles.
基金Supported by the National Natural Science Foundation of China （20176036）.
文摘Two methods of the modification of zeolite were employed： framework element modification and surface coating, and the influence of the zeolites before and after modification on the CO2 absorption was investigated. It was found that although hydrophobicity of zeolite could be obtained by means of the surficial organic coating in the method of surface coating _mod!fication, partial channel of zeolite would be plugged, as a result, leading to the surface area reducing greatly. Distinctively, the framework element modification method could maintain not only complete lattice structure and adsorption capability of zeolite, but would also obtain a good hydrophobic property. Consequently, significant enhancement on gas absorption by this modified zeolite was achieved and up to a maximum enhancement factor of 2.62. This shows that the solid particles with good enhancement role to gas absorption need not only good adsorptive capability but also certain hydrophobicity. An unsteady heterogeneous model was employed to predict enhancement factor and the calculated results agree well with the experimental data.
基金supported by the National Natural Science Foundation of China(Nos.41775155,41875160 and 41475119).
文摘This study investigates seasonal variations of mass absorption efficiency of elemental carbon(MAE_(EC))and possible influencing factors in urban Guangzhou of South China.Mass concentrations of elemental carbon(EC)and organic carbon(OC)in PM_(2.5) and aerosol absorption coefficient(b_(ap))at multi-wavelengths were simultaneously measured in four seasons of 2018-2019 at hourly resolution by a semi-continuous carbon analyzer and an aethalometer.Seasonal average mass concentrations of EC were in the range of 1.36-1.70μgC/m^(3) with a lower value in summer than in the other seasons,while those of OC were in the range of 4.70–6.49μgC/m^(3) with the lowest value in summer and the highest in autumn.Vehicle exhaust from local traffic was identified to be the predominant source of carbonaceous aerosols.The average aerosol absorption Angstrom exponents(AAE)were lower than 1.2 in four seasons,indicating EC and b_(ap) were closely related with vehicle exhaust.Seasonal MAE EC at 550 nm was 11.0,8.5,10.4 and 11.3 m^(2)/g in spring,summer,autumn,and winter,respectively.High MAE EC was related with the high mass ratio of non-carbonaceous aerosols to EC and high ambient relative humidity.
基金Project supported by the Postgraduate Innovation Foundation of Jiangsu Province,China (Grant No.CX09B 090Z)the Key Postgraduate Plan of Nanjing University of Science and Technology,China
文摘To increase the absorption in a thin layer of absorbing material （amorphous silicon, a-Si）, a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic （TM）-polarized light, but also for transverse electric （TE）-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.
基金Supported by the National Basic Research Program of China under Grant No 2011CB610300the National Natural Science Foundation of China under Grant Nos 11102148 and 11321062the Fundamental Research Funds for Central Universities of China
文摘We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter scale meso-slit matrix. Theoretical and numerical results reveal that this exotic phenomenon is attributed to the noticeable velocity and temperature gradients induced at the junctures of the micro- and meso-slits, which cause significant loss of sound energy as a result of viscous and thermal effects. It is demonstrated that the proposed thin multi-slit hybrid structure with micro-scale configuration is capable of controling low frequency noise with large wavelength, which is attractive for applications where the size and weight of a sound absorber are restricted.
基金supported by the National Natural Science Foundation of China under Grant No. G050104011004024the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. A0901040110018512026
文摘Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole approximation （DDA）,we study the absorption and scattering properties of two-dimensional square silver nanodisks （2D SSN） arrays on the single crystal silicon solar cell.Based on the effective reflective index model of the single crystal silicon solar cell,we investigate the optical enhancement absorption of light energy by varying the light incident direction,particle size,aspect ratio,and interparticle spacing of the silver nanodisks.The peak values and position of the optical extinction spectra of the 2D square arrays of noble metal nanodisks are obtained with the different array structures.
文摘An insulin-loaded emulsion system （IES） was developed as a hypoglycaemic drug for transmucosal delivery. The selected formulation was a stable oil/water emulsion system. The particles in the emulsion system were distributed evenly, and the particle size ranged from 20 to 260 nm（ average size ： 67.5 nm ）. Soybean lecithin played an important role in the emulsion system due to its abilities of acting as both absorption enhancer for insulin uptake through sublingual mucosa and oily phase for the emulsion system. The laser confocal scanning microscopic（LCSM） study showed that FITC-labelled insulin could penetrate the sublingual mucosa of rabbits, and the phase diagrams of the emulsion system suggested that soybean lecithin could take the place of oily phase to construct a stable emulsion system even if the traditional oil was absent. The applications of soybean lecithin as pharmaceutical biomaterial were extended for the further usage by present studies.
基金Project supported by the National Natural Science Foundation of China(Grant No.61405217)the Zhejiang Provincial Natural Science Foundation,China(Grant No.LY20F050001)+1 种基金the Anhui Polytechnic University Research Startup Foundation,China(Grant No.2020YQQ042)the Pre-research Project of Natural Science Foundation of Anhui Polytechnic University,China(Grant No.Xjky2020021)。
文摘The broadband absorption enhancement effect in ultrathin molybdenum disulfide(Mo S2)films is investigated.It is achieved by inserting the Mo S2 film between a dielectric film and a one-dimensional silver grating backed with a silver mirror.The broadband absorption enhancement in the visible region is achieved,which exhibits large integrated absorption and short-circuit current density for solar energy under normal incidence.The optical properties of the proposed absorber are found to be superior to those of a reference planar structure,which makes the proposed structure advantageous for practical photovoltaic application.Moreover,the integrated absorption and short-circuit current density can be maintained high for a wide range of incident angles.A qualitative understanding of such broadband absorption enhancement effect is examined by illustrating the electromagnetic field distribution at some selected wavelengths.The results pave the way for developing high-performance optoelectronic devices,such as solar cells,photodetectors,and modulators.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51132004,11474096,11604199,U1704145 and 11747101the Science and Technology Commission of Shanghai Municipality under Grant No 14JC1401500+1 种基金the Henan Provincial Natural Science Foundation of China under Grant No 182102210117the Higher Education Key Program of He’nan Province of China under Grant Nos 17A140025 and 16A140030
文摘We extend the third perturbation theory to study the polarization control behavior of the intermediate state absorption in Nd^（3＋）ions. The results show that coherent interference can occur between the single-photon and three-photon excitation pathways, and depends on the central frequency of the femtosecond laser field. Moreover,single-photon and three-photon absorptions have different polarization control efficiencies, and the relative weight of three-photon absorption in the whole excitation processes can increase with increasing the laser intensity.Therefore, the enhancement or suppression of the intermediate state absorption can be realized and manipulated by properly designing the intensity and central frequency of the polarization modulated femtosecond laser field.This research can not only enrich theoretical research methods for the up-conversion luminescence manipulation of rare-earth ions, but also can provide a clear physical picture for understanding and controlling multi-photon absorption in a multiple energy level system.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51132004,11474096 and 11604199the Science and Technology Commission of Shanghai Municipality under Grant No 14JC1401500the Higher Education Key Program of He'nan Province under Grant Nos 17A140025 and 16A140030
文摘The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited （TL）-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.
文摘Titanium-doped sapphire is an excellent laser crystal which has a bright future.But the residual infrared absorption in laser operation region of the crystal hindered the enhancement of the laser gain.Reducing the residual infrared absorption is the key to that the crystal goes from experimental prototypesto commercially available products.
基金Financial support from the Aeronautics Science Foundation of China(2017ZF52066)the National Nature Science Foundation of China(no.11575085)+2 种基金the Chinese Government Scholarship funded by China Scholarship Council(201806830052)the Postgraduate Research&Practice Innovation of Jiangsu Province(KYCX18_0277)the Qing Lan Project,Six Talent Peaks Project in Jiangsu Province(no.XCL-035)。
文摘Different kinds of hetero-structured ZnO/nanoporous carbon(NPC)composites with enhanced microwave absorption properties have been designed through a self-templated route by using zeolitic imidazolate framework(ZIF-8)as raw material.Thus,a series of samples with different dielectric features were obtained via calcination processes.Interestingly,the annealing temperatures during the carbonization procedures play a key role in the impedance matching and the dielectric relaxations for the final products composed of ZnO,NPC and nanopores.The heating temperatures could influence the degree of graphitization and the dielectric features.As a result,a maximum reflection loss of−25 dB with 1.55 mm can be achieved.In a word,this study confirms that the heating temperatures have important influences on dielectric as well as impedance matching for metal–organic frameworks,which is expected to be expanded to the design of many other efficient microwave absorbing materials.
基金supported by the National Natural Science Foundation of China(No.61975245)the Science and Technology Planning Project of Guangdong Province(No.2017A010103035).
文摘In this work,we design oxygen vacancy-rich BiOBr:Yb^(3+)/Er^(3+)(BYE-OV)ultrathin nanosheets,which can effectively enhance UC luminescence by oxygen vacancy engineering.Density functional theory calculations and UV-Vis-NIR absorption spectra reveal that the existence of oxygen vacancies leads to the formation of an intermediate band(IB)in the bandgap,which can enhance the light absorption ability and promote electron excitation and bandgap transitions(VB→CB,VB→IB and IB→CB),thereby providing the transfer of abundant electrons from the host to Er^(3+)ions.As a result,the emission intensity of green and red is exceptionally enhanced by 6.5 and 12 times respectively via introduced oxygen vacancies.Meanwhile,BYE-OV exhibits superior photocatalytic activity for the degradation of RhB under visible-NIR light irradiation.The enhanced activity can be mainly ascribed to enhanced photoabsorption in the visible-NIR region and improved UC luminescence.This work offers a new strategy for a rational design for enhancing UC luminescence,which has potential for applications in visible-NIR light photocatalysis.
基金supported by the financial support from Natural Science Foundation of China(21776053 and 21676065)。
文摘Magnetic carbon-based composites are the most attractive candidates for electromagnetic(EM)absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magnetic branches.Metal-organic frameworks(MOFs)have demonstrated their great potential as sacrificing precursors of magnetic metals/carbon composites,because they provide a good platform to achieve high dispersion of magnetic nanoparticles in carbon matrix.Nevertheless,the chemical composition and microstructure of these composites are always highly dependent on their precursors and cannot promise an optimal EM state favorable for EM absorption,which more or less discount the superiority of MOFs-derived strategy.It is hence of great importance to develop some accompanied methods that can regulate EM properties of MOFs-derived magnetic carbon-based composites e ectively.This review comprehensively introduces recent advancements on EM absorption enhancement in MOFs-derived magnetic carbon-based composites and some available strategies therein.In addition,some challenges and prospects are also proposed to indicate the pending issues on performance breakthrough and mechanism exploration in the related field.
基金supported by the National Key R&D Program of China (No. 2020YFE0201700)the National Mega-project for Innovative Drugs (No. 2019ZX09721001)+3 种基金the National Natural Science Foundation of China (No. 81673378)the Liaoning Revitalization Talents Program (No. XLYC1908031)the Project of Liaoning Provincial Department of Education (No. 2019LQN07)the PhD Research Startup Foundation of Liaoning Province (No. 2020-BS-128)。
文摘Efficient oral delivery of drugs treating brain diseases has long been a challenging topic faced by the drug delivery community. Fortunately, polyester nanoparticles offer certain solutions to this problem. This review article firstly describes the main obstacles faced by oral administered brain targeting, including:(1)instability in the gastrointestinal tract;(2) poor penetration of the intestinal mucosa and epithelium;(3)blood clearance;and(4) restriction by the BBB. Then the key factors influencing brain-targeting efficiency of orally administered polyester nanoparticles are also discussed, such as size, shape and surface properties. Finally, recent brain-targeting delivery strategies using oral polyester nanoparticles as carriers and their effects on brain drugs transport are reviewed, and the delivery ‘as a whole’ strategy of polyester nanoparticles will provide new insight for oral brain-targeting delivery. And by combination of multiple strategies, both the stability and permeability of polyester nanoparticles can be greatly improved for oral brain drug delivery.
