The inevitable release of engineered silver nanoparticles（Ag NPs） into aquatic environments has drawn great concerns about its environmental toxicity and safety. Although aggregation and transformation play crucial ...The inevitable release of engineered silver nanoparticles（Ag NPs） into aquatic environments has drawn great concerns about its environmental toxicity and safety. Although aggregation and transformation play crucial roles in the transport and toxicity of Ag NPs, how the water chemistry of environmental waters influences the aggregation and transformation of engineered Ag NPs is still not well understood. In this study, the aggregation of polyvinylpyrrolidone（PVP） coated Ag NPs was investigated in eight typical environmental water samples（with different ionic strengths, hardness, and dissolved organic matter（DOM） concentrations） by using UV–visible spectroscopy and dynamic light scattering. Raman spectroscopy was applied to probe the interaction of DOM with the surface of Ag NPs. Further, the photo-transformation and morphology changes of Ag NPs in environmental waters were studied by UV–visible spectroscopy, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The results suggested that both electrolytes（especially Ca2＋and Mg2＋） and DOM in the surface waters are key parameters for Ag NP aggregation, and sunlight could accelerate the morphology change, aggregation, and further sedimentation of Ag NPs. This water chemistry controlled aggregation and photo-transformation should have significant environmental impacts on the transport and toxicity of Ag NPs in the aquatic environments.展开更多
More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation beha...More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and p H all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks.展开更多
Citrate-reduced silver nanoparticles (Ag-NPs) are used extensively for surface-enhanced Raman scattering (SERS) studies, but are typically found to aggregate using an aggregation agent. This study is aimed at developi...Citrate-reduced silver nanoparticles (Ag-NPs) are used extensively for surface-enhanced Raman scattering (SERS) studies, but are typically found to aggregate using an aggregation agent. This study is aimed at developing a simple, stable, and reproducible aggregated method for Ag-NPs without any aggregation agents in aqueous solutions. The aggregation is induced by the process of centrifugation, water washing and ultrasonication. A mechanism based on the nonuniform distribution of capping ligands is proposed to account for the aggregated structure formation. UV-Vis-NIR extinction spectra and TEM allowed us to identify the existence of Ag-NPs aggregation. Further, due to the polydisperse mixture of Ag-NPs (20~65 nm) used in the present work, Ag-NPs are aggregated closely, which contribute to the observation of low-concentration SERS from the residual citrate layer or even the single-molecule SERS of R6Gon aggregation. After the evaporation of droplet of Ag-NPs aggregation on the Si substrate, citrate or R6Gcould also be detected but with marked redor blue-shifts.展开更多
The nanotechnology industry advances rapidly,and at the vanguard are the promising silver nanoparticles（Ag NPs）,which have diverse applications.These nanometer-sized particles have been shown to inhibit the ability ...The nanotechnology industry advances rapidly,and at the vanguard are the promising silver nanoparticles（Ag NPs）,which have diverse applications.These nanometer-sized particles have been shown to inhibit the ability of bacteria to produce adenosine triphosphate（ATP）,a molecule necessary for chemical energy transport in cells.The antimicrobial properties of Ag NPs（and Ag＋）make them valued antibacterial展开更多
Dispersion and aggregation of nanoparticles in aqueous solutions are important factors for safe application of nanoparticles. In this study, dispersion and aggregation of nano-TiO2 in aqueous solutions containing vari...Dispersion and aggregation of nanoparticles in aqueous solutions are important factors for safe application of nanoparticles. In this study, dispersion and aggregation of nano-TiO2 in aqueous solutions containing various anions were investigated. The influences of anion concentration and valence on the aggregation size, zeta potential and aggregation kinetics were individually investigated. Results showed that the zeta potential decreased from 19.8 to-41.4 mV when PO4^（3-） concentration was increased from 0 to 50 mg/L, while the corresponding average size of nano-TiO2 particles decreased from 613.2 to 540.3 nm. Both SO4^（2-） and NO3^-enhanced aggregation of nano-TiO2in solution. As SO4^（2-） concentration was increased from 0 to 500 mg/L, the zeta potential decreased from 19.8 to 1.4 mV, and aggregate sizes increased from 613.2 to 961.3 nm.The trend for NO3^- fluctuation was similar to that for SO4^（2-） although the range of variation for NO3^- was relatively narrow. SO4^（2-） and NO3^-accelerated the aggregation rapidly, while PO4^（3-） did so slowly. These findings facilitate the understanding of aggregation and dispersion mechanisms of nano-TiO2 in aqueous solutions in the presence of anions of interest.展开更多
The application of selenium nanoparticles(SeNPs)as nanofertilizers may lead to the release of SeNPs into aquatic systems.However,the environmental behavior of SeNPs is rarely studied.In this study,using alginate-coate...The application of selenium nanoparticles(SeNPs)as nanofertilizers may lead to the release of SeNPs into aquatic systems.However,the environmental behavior of SeNPs is rarely studied.In this study,using alginate-coated SeNPs(Alg-SeNPs)and polyvinyl alcohol-coated SeNPs(PVA-SeNPs)as models,we systematically investigated the aggregation and stability of SeNPs under various water conditions.PVA-SeNPs were highly stable in mono-and polyvalent electrolytes,probably due to the strong steric hindrance of the capping agent.Alg-SeNPs only suffered from a limited increase in size,even at 2500 mmol/L NaCl and 200 mmol/L MgCl_(2),while they underwent apparent aggregation in CaCl_(2) and LaCl_(3) solutions.The binding of Ca^(2+) and La^(3+) with the guluronic acid part in alginate induced the formation of cross-linking aggregates.Natural organic matter enhanced the stability of Alg-SeNPs in monovalent electrolytes,while accelerated the attachment of Alg-SeNPs in polyvalent electrolytes,due to the cation bridge effects.The long-term stability of SeNPs in natural water showed that the aggregation sizes of Alg-SeNPs and PVA-SeNPs increased to several hundreds of nanometers or above 10μm after 30 days,implying that SeNPs may be suspended in the water column or further settle down,depending on the surrounding water chemistry.The study may contribute to the deep insight into the fate and mobility of SeNPs in the aquatic environment.The varying fate of SeNPs in different natural waters also suggests that the risks of SeNPs to organisms living in diverse depths in the aquatic compartment should be concerned.展开更多
Deposition of β-amyloid protein(Aβ) is the main hallmark of Alzheimer's disease(AD), and it has been well recognized that Cu^(2+)-mediated Aβ aggregation plays a crucial role in AD pathological processes.Cu^(2+...Deposition of β-amyloid protein(Aβ) is the main hallmark of Alzheimer's disease(AD), and it has been well recognized that Cu^(2+)-mediated Aβ aggregation plays a crucial role in AD pathological processes.Cu^(2+)binding to Aβ can promote the production of reactive oxygen species(ROS) through Fenton-like reactions and produce more toxic Aβ-Cu^(2+)species under Cu^(2+)stimulation. Thus, the development of nanomaterials that can inhibit Cu^(2+)-mediated Aβ aggregation and degrade Aβ-Cu^(2+)complexes is considered an effective strategy for the prevention and treatment of AD. In this study, polydopamine nanoparticles(PDA NPs) were prepared and the results reveal that PDA NPs potently inhibit Cu^(2+)-mediated Aβaggregation and effectively reduce the formation of Aβ-Cu^(2+)complexes. In vitro experiments show that PDA NPs efficiently eliminate ROS generation catalyzed by Cu^(2+)or Aβ-Cu^(2+)complexes, thus rescuing cultured cells by reducing intracellular ROS levels. More importantly, PDA NPs can depolymerize Aβ-Cu^(2+)complexes, and the degradation of Aβ-Cu^(2+)complexes is promoted by near-infrared light irradiation due to their high photothermal conversion ability. In vivo studies reveal that PDA NPs significantly reduce the deposition of Aβ plaques in the presence of Cu^(2+)and extend the lifespan of AD nematodes from 11 to 14 d. Thus, the PDA NPs developed herein are multifunctional against Cu^(2+)-mediated Aβ aggregation for the potential prevention and treatment of AD.展开更多
TiO2 nanoparticles（NPs） could adversely impact aquatic ecosystems. However, the aggregation of these NPs could attenuate this effect. In this work, the biological effects of TiO2 NPs on a marine microalgae Isochrysi...TiO2 nanoparticles（NPs） could adversely impact aquatic ecosystems. However, the aggregation of these NPs could attenuate this effect. In this work, the biological effects of TiO2 NPs on a marine microalgae Isochrysis galbana were investigated. The aggregation kinetics of TiO2 NPs under different conditions was also investigated to determine and understand these effects. Results showed that, though TiO2 NPs had no obvious impact on the size and reproducibility of algal cells under testing conditions, they caused a negative effect on algal chlorophyll, which led to a reduction in photosynthesis. Furthermore, fast aggregation of TiO2 NPs occurred under all conditions, especially at the pH close to the p Hzpc. Increasing ionic strength and NP concentration also enhanced the aggregation rate.The aggregation and the following sedimentation of TiO2 NPs reduced their adverse effects on I. galbana.展开更多
A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles（Au NPs） is presented. 4-Mercaptophenylboronic acid（MPBA） induces the aggregation of Au NPs, leading ...A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles（Au NPs） is presented. 4-Mercaptophenylboronic acid（MPBA） induces the aggregation of Au NPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on Au NPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio（A（519）/A（640）） was linear with fructose concentration in the range of 0.032–0.96 μmol/L（R^2= 0.996）, with a low detection limit of 0.01 μmol/L（S/N = 3）. Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide（glucose, mannose, galactose,lactose and saccharose）. With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose.展开更多
Photodynamic therapy(PDT) employs accumulation of photosensitizers(PSs) in malignant tumor tissue followed by the light-induced generation of cytotoxic reactive oxygen species to kill the tumor cells. The success of P...Photodynamic therapy(PDT) employs accumulation of photosensitizers(PSs) in malignant tumor tissue followed by the light-induced generation of cytotoxic reactive oxygen species to kill the tumor cells. The success of PDT depends on optimal PS dosage that is matched with the ideal power of light. This in turn depends on PS accumulation in target tissue and light administration time and period.As theranostic nanomedicine is driven by multifunctional therapeutics that aim to achieve targeted tissue delivery and image-guided therapy, fluorescent PS nanoparticle(NP)accumulation in target tissues can be ascertained through fluorescence imaging to optimize the light dose and administration parameters. In this regard, zebrafish larvae provide a unique transparent in vivo platform to monitor fluorescent PS bio-distribution and their therapeutic efficiency. Using fluorescent PS NPs with unique aggregation-induced emission characteristics, we demonstrate for the first time the real-time visualization of polymeric NP accumulation in tumor tissue and, more importantly, the best time to conduct PDT using transgenic zebrafish larvae with inducible liver hyperplasia as an example.展开更多
A sensitivity analysis is performed to analyze the effects of the nanoparticle(NP)aggregation and thermal radiation on heat transport of the nanoliquids(titania based on ethylene glycol)over a vertical cylinder.The op...A sensitivity analysis is performed to analyze the effects of the nanoparticle(NP)aggregation and thermal radiation on heat transport of the nanoliquids(titania based on ethylene glycol)over a vertical cylinder.The optimization of heat transfer rate and friction factor is performed for NP volume fraction(1%≤φ≤3%),radiation parameter(1≤R_(t)≤3),and mixed convection parameter(1.5≤λ≤2.5)via the facecentered central composite design(CCD)and the response surface methodology(RSM).The modified Krieger and Dougherty model(MKDM)for dynamic viscosity and the Bruggeman model(BM)for thermal conductivity are utilized to simulate nanoliquids with the NP aggregation aspect.The complicated nonlinear problem is treated numerically.It is found that the temperature of nanoliquid is enhanced due to the aggregation of NPs.The friction factor is more sensitive to the volume fraction of NPs than the thermal radiation and the mixed convection parameter.Furthermore,the heat transport rate is more sensitive to the effect of radiative heat compared with the NP volume fraction and mixed convection parameter.展开更多
1 Introduction Nanoparticles are widely found in the ductile shear zone and it is considered to have a close relation with faulting.The sizes of these nanoparticles are generallyless than 100 nm.They have a variety of...1 Introduction Nanoparticles are widely found in the ductile shear zone and it is considered to have a close relation with faulting.The sizes of these nanoparticles are generallyless than 100 nm.They have a variety of morphologies like globular structure rod-like and tubular,by the order aggregating of these nanoparticles various aggregations展开更多
We present the results of molecular dynamics simulations of net positively charged fullerene nanoparticles in salt- free and salt-added solution. The aggregation of fullerene （C60）-like nanoparticle and counterion a...We present the results of molecular dynamics simulations of net positively charged fullerene nanoparticles in salt- free and salt-added solution. The aggregation of fullerene （C60）-like nanoparticle and counterion are studied in detail as a function of temperatures and a finite salt concentration. Our simulations show that the strong conformation changes as temperature changes. The net positively-charged nanoparticles do not repel each other but are condensed under proper temperatures. If salts are added, the aggregated nanoparticles will be disaggregated due to the Debye screening effect.展开更多
The current exploration focuses on the ethylene glycol(EG)based nanoliquid flow in a microchannel.The effectiveness of the internal heat source and linear radiation is reflected in the present investigation.The estima...The current exploration focuses on the ethylene glycol(EG)based nanoliquid flow in a microchannel.The effectiveness of the internal heat source and linear radiation is reflected in the present investigation.The estimation of suitable thermal conductivity model has affirmative impact on the convective heat transfer phenomenon.The examination is conceded with the nanoparticle aggregation demonstrated by the Maxwell-Bruggeman and Krieger-Dougherty models which tackle the formation of nanolayer.These models effectively describe the thermal conductivity and viscosity correspondingly.The dimensionless mathematical expressions are solved numerically by the Runge Kutta Fehlberg approach.A higher thermal field is attained for the Bruggeman model due to the formation of thermal bridge.A second law analysis is carried out to predict the sources of irreversibility associated with the thermal system.It is remarked that lesser entropy generation is obtained for the aggregation model.The entropy generation rate declines with the slip flow and the thermal heat flux.A notable enhancement in the Bejan number is attained by increasing the Biot number.It is established that the nanoparticle aggragation model exhibits a higher Bejan number in comparision with the usual flow model.展开更多
Melanin, the main photoreceptor in living organics, is largely abundant in pigmented hair tissues. Its promising properties have been widely studied in order to fully explore the corresponding applications. However, t...Melanin, the main photoreceptor in living organics, is largely abundant in pigmented hair tissues. Its promising properties have been widely studied in order to fully explore the corresponding applications. However, the photodegradating and aggregating natures of melanin, to some extent, restrict the development of this eco-friendly biomaterial. This study is conducted to overcome both disadvantages by a mature method that coating the original melanin nanoparticles with silica as shells. The results revealed that the aggregation of the melanin/silica nanoparticles (MSNP) was decreased obviously by a 5 h coating and appeared a uniformly mono-dispersed solution. The MSNP that coated for 20 h provided an efficient protection on the photodegradation of the melanin with a 50% maintenance of the melanin content compared with 16% of original melanin and 2% of MSNP-5 h.展开更多
The heat transfer between two corresponding plates,disks,and concentric pipes has many applications,including water cleansing and lubrication.Furthermore,TiO_(2)-water-based nanofluids are used widely because it is us...The heat transfer between two corresponding plates,disks,and concentric pipes has many applications,including water cleansing and lubrication.Furthermore,TiO_(2)-water-based nanofluids are used widely because it is useful for operating and controlling the temperature,especially in photovoltaic technology and solar panels.Motivated by these applications,the current study is based on the nanoparticle aggregation effect on magnetohydrodynamics(MHD)flow via rotating parallel plates with the chemical reaction.To achieve maximum heat transportation,the Bruggeman model is used to adapt the Maxwell model.Also,melting and thermal radiation effects are considered in the modeling to discuss heat transport.The Runge-Kutta-Fehlberg 4th−5th order method is used to attain numerical solutions.The main focus of this study is to see the thermodynamic behavior considering several aspects of nanoparticle aggregation.The heat transfer rate between the parallel plates is enhanced by improving the thermophoresis,radiation,and Brownian motion parameters.The rise in Schmidt number and chemical reaction rate parameter decreases the concentration distribution.This study will be helpful in enhancing the thermal efficiency of photovoltaic technology in solar plates,water purifying,thermal management of electronic devices,designing effective cooling systems,and other sustainable technologies.展开更多
Using gas-liquid segmented micromixers to prepare nanoparticles that have a homogeneous particle size, controllable shape, and monodispersity advantages. Although nanoparticle aggregation within a microfluid has been ...Using gas-liquid segmented micromixers to prepare nanoparticles that have a homogeneous particle size, controllable shape, and monodispersity advantages. Although nanoparticle aggregation within a microfluid has been shown to be affected by the shear effect, the shear effect triggering conditions in gasliquid two-phase flow is unclear and the aggregation behavior of nanoparticles under the shear effect is difficult to predict, resulting in uncontrollable physical and chemical properties of nanoparticle aggregates. In this study, a numerical simulation of nanoparticle aggregation in gas-liquid two-phase flow under the shear effect is performed using the CFD-DEM method. Then, the effects of total flow rate,gas-liquid two-phase flow ratio, and particle volume fraction on particle aggregation were analyzed to achieve control of particle aggregation shape and size. Meanwhile, the triggering mechanism of the shear effect and the mechanism of the shear effect on the aggregation of nanoparticles were clarified. The results show that increasing the total flow rate or decreasing the gas-liquid two-phase flow rate ratio can induce the shear effect, which reduces the particle aggregation size and makes the morphology tend to be spherical. Moreover, increasing the particle volume fraction, and total flow rate or decreasing the gas-liquid two-phase flow rate ratio also increases the number of particle collisions and induce interparticle adhesion. Hence, particle adhesion and the shear effect compete with each other and together affect particle aggregation.展开更多
The present work aims to ascertain the mechanisms of surfactant（dodecylbenzene sulfonate; DBS） effects on the aggregation behaviors of TiO2 nanoparticles（TiO2-NPs） in natural water samples. Aggregation experiments...The present work aims to ascertain the mechanisms of surfactant（dodecylbenzene sulfonate; DBS） effects on the aggregation behaviors of TiO2 nanoparticles（TiO2-NPs） in natural water samples. Aggregation experiments were conducted at a TiO2-NPs concentration of 10 mg/L in deionized water and in natural water samples via dynamic light scattering and Zeta potential determination. Average attachment efficiency was calculated to compare the aggregation behaviors of nanoparticles in the two aqueous media. Results showed that the effects of DBS on aggregation could be interpreted by both Derjaguin–Landau–Verwey–Overbeek（DLVO） and non-DLVO mechanisms. In natural water samples,aggregation did not occur rapidly and was able to develop slowly under all conditions, and the roles of DBS were obvious at high DBS concentration owing to the impacts of inherent components of natural water samples, such as colloids and natural organic compounds.Future aggregation studies should concentrate on multi-factor, multi-colloidal and dynamic aspects under similar environmental conditions.展开更多
In aqueous environment,organic matters may exert impacts on the aggregation behaviors of titanium dioxide nanoparticles( TiO2-NPs). Owing to the deficiency of studies on the aggregation of TiO2-NPs in the presence of ...In aqueous environment,organic matters may exert impacts on the aggregation behaviors of titanium dioxide nanoparticles( TiO2-NPs). Owing to the deficiency of studies on the aggregation of TiO2-NPs in the presence of synthetic organic compound,this study used linear alkylbenzene sulfonate( LAS) as a representative to evaluate the effects of TiO2-NPs concentration( 1-10 mg / L),LAS concentration( 0- 1 mg / L),pH( 4- 8)and ionic strength( NaCl,CaCl2; 5- 20 mM) during aggregation of TiO2-NPs suspensions based on the detection of hydrodynamic diameters and electrophoretic mobilities and the calculation of interaction energies.The results showed that the TiO2-NPs in the presence of LAS are more stable than that in the absence of LAS.With the increase of ionic strength,the hydrodynamic diameter of NPs decreases,and the existence of LAS changes the point of zero charge from 5. 4 to a lower value and thus alteres the aggregation behaviors of TiO2-NPs. The present study suggests that the LAS has a significant impact to the transportation and transformation of nanoparticles in aqueous environment.展开更多
This work aims to analyze the flow of electrically conducting MWCNTs-nanofluid over a stretching cylinder with the aggregation and non-aggregation effects of nanoparticles. The working fluid comprised a combination of...This work aims to analyze the flow of electrically conducting MWCNTs-nanofluid over a stretching cylinder with the aggregation and non-aggregation effects of nanoparticles. The working fluid comprised a combination of water and ethylene glycol, with volumetric proportions of (50:50) considered. Convective boundary constraints and modified Fourier law are implemented in heat transmission assessment. The mathematical flow model is formulated in the form of PDEs and is transformed into ODEs via similarity transformation. Numerical outcomes will be obtained with the use of the bvp4c technique and will be displayed with the help of graphs and tables. The results show that the surface drag coefficient is enhanced in the case of aggregation of nanoparticles whereas heat transfer rate is enhanced in the non-aggregation effect of nanoparticles. Furthermore, the temperature distribution enhances the increasing values of particle volume fraction in the case of aggregation effects of nanoparticles whereas temperature distribution lowers in the case of non-aggregation effect of nanoparticles. .展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB14020101)the External Cooperation Program of Chinese Academy of Sciences (No.GJHZ1206)+1 种基金the National Natural Science Foundation of China (No.21337004)the Young Scientists Fund of RCEES (No.RCEES-QN-20130028F)
文摘The inevitable release of engineered silver nanoparticles（Ag NPs） into aquatic environments has drawn great concerns about its environmental toxicity and safety. Although aggregation and transformation play crucial roles in the transport and toxicity of Ag NPs, how the water chemistry of environmental waters influences the aggregation and transformation of engineered Ag NPs is still not well understood. In this study, the aggregation of polyvinylpyrrolidone（PVP） coated Ag NPs was investigated in eight typical environmental water samples（with different ionic strengths, hardness, and dissolved organic matter（DOM） concentrations） by using UV–visible spectroscopy and dynamic light scattering. Raman spectroscopy was applied to probe the interaction of DOM with the surface of Ag NPs. Further, the photo-transformation and morphology changes of Ag NPs in environmental waters were studied by UV–visible spectroscopy, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The results suggested that both electrolytes（especially Ca2＋and Mg2＋） and DOM in the surface waters are key parameters for Ag NP aggregation, and sunlight could accelerate the morphology change, aggregation, and further sedimentation of Ag NPs. This water chemistry controlled aggregation and photo-transformation should have significant environmental impacts on the transport and toxicity of Ag NPs in the aquatic environments.
基金supported by the National Natural Science Foundation of China(Nos.51808530 and 51778604)。
文摘More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and p H all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks.
文摘Citrate-reduced silver nanoparticles (Ag-NPs) are used extensively for surface-enhanced Raman scattering (SERS) studies, but are typically found to aggregate using an aggregation agent. This study is aimed at developing a simple, stable, and reproducible aggregated method for Ag-NPs without any aggregation agents in aqueous solutions. The aggregation is induced by the process of centrifugation, water washing and ultrasonication. A mechanism based on the nonuniform distribution of capping ligands is proposed to account for the aggregated structure formation. UV-Vis-NIR extinction spectra and TEM allowed us to identify the existence of Ag-NPs aggregation. Further, due to the polydisperse mixture of Ag-NPs (20~65 nm) used in the present work, Ag-NPs are aggregated closely, which contribute to the observation of low-concentration SERS from the residual citrate layer or even the single-molecule SERS of R6Gon aggregation. After the evaporation of droplet of Ag-NPs aggregation on the Si substrate, citrate or R6Gcould also be detected but with marked redor blue-shifts.
文摘The nanotechnology industry advances rapidly,and at the vanguard are the promising silver nanoparticles（Ag NPs）,which have diverse applications.These nanometer-sized particles have been shown to inhibit the ability of bacteria to produce adenosine triphosphate（ATP）,a molecule necessary for chemical energy transport in cells.The antimicrobial properties of Ag NPs（and Ag＋）make them valued antibacterial
基金supported by the International S&T Cooperation Program of China(No.2015DFG92750)the National Natural Science Foundation of China(No.51478172)the Department of Science and Technology of Hunan Province(No.2014GK1012)
文摘Dispersion and aggregation of nanoparticles in aqueous solutions are important factors for safe application of nanoparticles. In this study, dispersion and aggregation of nano-TiO2 in aqueous solutions containing various anions were investigated. The influences of anion concentration and valence on the aggregation size, zeta potential and aggregation kinetics were individually investigated. Results showed that the zeta potential decreased from 19.8 to-41.4 mV when PO4^（3-） concentration was increased from 0 to 50 mg/L, while the corresponding average size of nano-TiO2 particles decreased from 613.2 to 540.3 nm. Both SO4^（2-） and NO3^-enhanced aggregation of nano-TiO2in solution. As SO4^（2-） concentration was increased from 0 to 500 mg/L, the zeta potential decreased from 19.8 to 1.4 mV, and aggregate sizes increased from 613.2 to 961.3 nm.The trend for NO3^- fluctuation was similar to that for SO4^（2-） although the range of variation for NO3^- was relatively narrow. SO4^（2-） and NO3^-accelerated the aggregation rapidly, while PO4^（3-） did so slowly. These findings facilitate the understanding of aggregation and dispersion mechanisms of nano-TiO2 in aqueous solutions in the presence of anions of interest.
基金supported by the National Natural Science Foundation of China(Nos.22076198,42192571,and 21827815).
文摘The application of selenium nanoparticles(SeNPs)as nanofertilizers may lead to the release of SeNPs into aquatic systems.However,the environmental behavior of SeNPs is rarely studied.In this study,using alginate-coated SeNPs(Alg-SeNPs)and polyvinyl alcohol-coated SeNPs(PVA-SeNPs)as models,we systematically investigated the aggregation and stability of SeNPs under various water conditions.PVA-SeNPs were highly stable in mono-and polyvalent electrolytes,probably due to the strong steric hindrance of the capping agent.Alg-SeNPs only suffered from a limited increase in size,even at 2500 mmol/L NaCl and 200 mmol/L MgCl_(2),while they underwent apparent aggregation in CaCl_(2) and LaCl_(3) solutions.The binding of Ca^(2+) and La^(3+) with the guluronic acid part in alginate induced the formation of cross-linking aggregates.Natural organic matter enhanced the stability of Alg-SeNPs in monovalent electrolytes,while accelerated the attachment of Alg-SeNPs in polyvalent electrolytes,due to the cation bridge effects.The long-term stability of SeNPs in natural water showed that the aggregation sizes of Alg-SeNPs and PVA-SeNPs increased to several hundreds of nanometers or above 10μm after 30 days,implying that SeNPs may be suspended in the water column or further settle down,depending on the surrounding water chemistry.The study may contribute to the deep insight into the fate and mobility of SeNPs in the aquatic environment.The varying fate of SeNPs in different natural waters also suggests that the risks of SeNPs to organisms living in diverse depths in the aquatic compartment should be concerned.
基金funded by the National Natural Science Foundation of China (21978207 and 21621004)the Natural Science Foundation of Tianjin from Tianjin Municipal Science and Technology Commission (19JCZDJC36800)。
文摘Deposition of β-amyloid protein(Aβ) is the main hallmark of Alzheimer's disease(AD), and it has been well recognized that Cu^(2+)-mediated Aβ aggregation plays a crucial role in AD pathological processes.Cu^(2+)binding to Aβ can promote the production of reactive oxygen species(ROS) through Fenton-like reactions and produce more toxic Aβ-Cu^(2+)species under Cu^(2+)stimulation. Thus, the development of nanomaterials that can inhibit Cu^(2+)-mediated Aβ aggregation and degrade Aβ-Cu^(2+)complexes is considered an effective strategy for the prevention and treatment of AD. In this study, polydopamine nanoparticles(PDA NPs) were prepared and the results reveal that PDA NPs potently inhibit Cu^(2+)-mediated Aβaggregation and effectively reduce the formation of Aβ-Cu^(2+)complexes. In vitro experiments show that PDA NPs efficiently eliminate ROS generation catalyzed by Cu^(2+)or Aβ-Cu^(2+)complexes, thus rescuing cultured cells by reducing intracellular ROS levels. More importantly, PDA NPs can depolymerize Aβ-Cu^(2+)complexes, and the degradation of Aβ-Cu^(2+)complexes is promoted by near-infrared light irradiation due to their high photothermal conversion ability. In vivo studies reveal that PDA NPs significantly reduce the deposition of Aβ plaques in the presence of Cu^(2+)and extend the lifespan of AD nematodes from 11 to 14 d. Thus, the PDA NPs developed herein are multifunctional against Cu^(2+)-mediated Aβ aggregation for the potential prevention and treatment of AD.
基金supported by the China Scholarship Council through a State-Sponsored Scholarship Program, NSF of China (No. 21307019)the Public Science and Technology Research Fund Projects of Ocean (No. 201505034)+2 种基金the Zhejiang Provincial Natural Science Foundation (Nos. LY14D060007 and LQ16D060006)National Key Research and Development Program (No. 2016YFC1402405)support from the Environment Research Center (ERC) at the Missouri University of Science and Technology, Rolla, Missouri, USA
文摘TiO2 nanoparticles（NPs） could adversely impact aquatic ecosystems. However, the aggregation of these NPs could attenuate this effect. In this work, the biological effects of TiO2 NPs on a marine microalgae Isochrysis galbana were investigated. The aggregation kinetics of TiO2 NPs under different conditions was also investigated to determine and understand these effects. Results showed that, though TiO2 NPs had no obvious impact on the size and reproducibility of algal cells under testing conditions, they caused a negative effect on algal chlorophyll, which led to a reduction in photosynthesis. Furthermore, fast aggregation of TiO2 NPs occurred under all conditions, especially at the pH close to the p Hzpc. Increasing ionic strength and NP concentration also enhanced the aggregation rate.The aggregation and the following sedimentation of TiO2 NPs reduced their adverse effects on I. galbana.
文摘A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles（Au NPs） is presented. 4-Mercaptophenylboronic acid（MPBA） induces the aggregation of Au NPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on Au NPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio（A（519）/A（640）） was linear with fructose concentration in the range of 0.032–0.96 μmol/L（R^2= 0.996）, with a low detection limit of 0.01 μmol/L（S/N = 3）. Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide（glucose, mannose, galactose,lactose and saccharose）. With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose.
基金financial support from National Research Foundation Investigatorship (R279-000-444-281)National University of Singapore (R279-000-482-133)
文摘Photodynamic therapy(PDT) employs accumulation of photosensitizers(PSs) in malignant tumor tissue followed by the light-induced generation of cytotoxic reactive oxygen species to kill the tumor cells. The success of PDT depends on optimal PS dosage that is matched with the ideal power of light. This in turn depends on PS accumulation in target tissue and light administration time and period.As theranostic nanomedicine is driven by multifunctional therapeutics that aim to achieve targeted tissue delivery and image-guided therapy, fluorescent PS nanoparticle(NP)accumulation in target tissues can be ascertained through fluorescence imaging to optimize the light dose and administration parameters. In this regard, zebrafish larvae provide a unique transparent in vivo platform to monitor fluorescent PS bio-distribution and their therapeutic efficiency. Using fluorescent PS NPs with unique aggregation-induced emission characteristics, we demonstrate for the first time the real-time visualization of polymeric NP accumulation in tumor tissue and, more importantly, the best time to conduct PDT using transgenic zebrafish larvae with inducible liver hyperplasia as an example.
文摘A sensitivity analysis is performed to analyze the effects of the nanoparticle(NP)aggregation and thermal radiation on heat transport of the nanoliquids(titania based on ethylene glycol)over a vertical cylinder.The optimization of heat transfer rate and friction factor is performed for NP volume fraction(1%≤φ≤3%),radiation parameter(1≤R_(t)≤3),and mixed convection parameter(1.5≤λ≤2.5)via the facecentered central composite design(CCD)and the response surface methodology(RSM).The modified Krieger and Dougherty model(MKDM)for dynamic viscosity and the Bruggeman model(BM)for thermal conductivity are utilized to simulate nanoliquids with the NP aggregation aspect.The complicated nonlinear problem is treated numerically.It is found that the temperature of nanoliquid is enhanced due to the aggregation of NPs.The friction factor is more sensitive to the volume fraction of NPs than the thermal radiation and the mixed convection parameter.Furthermore,the heat transport rate is more sensitive to the effect of radiative heat compared with the NP volume fraction and mixed convection parameter.
基金supported by Natural Science Foundation of China(Project No.41206035,41602231)The National Nature Science Foundation of Guangdong Province(Project No.2015A030313157)
文摘1 Introduction Nanoparticles are widely found in the ductile shear zone and it is considered to have a close relation with faulting.The sizes of these nanoparticles are generallyless than 100 nm.They have a variety of morphologies like globular structure rod-like and tubular,by the order aggregating of these nanoparticles various aggregations
基金Project supported by the Natural Science Foundation of Fujian Province of China(Grant No.2012J05008)
文摘We present the results of molecular dynamics simulations of net positively charged fullerene nanoparticles in salt- free and salt-added solution. The aggregation of fullerene （C60）-like nanoparticle and counterion are studied in detail as a function of temperatures and a finite salt concentration. Our simulations show that the strong conformation changes as temperature changes. The net positively-charged nanoparticles do not repel each other but are condensed under proper temperatures. If salts are added, the aggregated nanoparticles will be disaggregated due to the Debye screening effect.
文摘The current exploration focuses on the ethylene glycol(EG)based nanoliquid flow in a microchannel.The effectiveness of the internal heat source and linear radiation is reflected in the present investigation.The estimation of suitable thermal conductivity model has affirmative impact on the convective heat transfer phenomenon.The examination is conceded with the nanoparticle aggregation demonstrated by the Maxwell-Bruggeman and Krieger-Dougherty models which tackle the formation of nanolayer.These models effectively describe the thermal conductivity and viscosity correspondingly.The dimensionless mathematical expressions are solved numerically by the Runge Kutta Fehlberg approach.A higher thermal field is attained for the Bruggeman model due to the formation of thermal bridge.A second law analysis is carried out to predict the sources of irreversibility associated with the thermal system.It is remarked that lesser entropy generation is obtained for the aggregation model.The entropy generation rate declines with the slip flow and the thermal heat flux.A notable enhancement in the Bejan number is attained by increasing the Biot number.It is established that the nanoparticle aggragation model exhibits a higher Bejan number in comparision with the usual flow model.
文摘Melanin, the main photoreceptor in living organics, is largely abundant in pigmented hair tissues. Its promising properties have been widely studied in order to fully explore the corresponding applications. However, the photodegradating and aggregating natures of melanin, to some extent, restrict the development of this eco-friendly biomaterial. This study is conducted to overcome both disadvantages by a mature method that coating the original melanin nanoparticles with silica as shells. The results revealed that the aggregation of the melanin/silica nanoparticles (MSNP) was decreased obviously by a 5 h coating and appeared a uniformly mono-dispersed solution. The MSNP that coated for 20 h provided an efficient protection on the photodegradation of the melanin with a 50% maintenance of the melanin content compared with 16% of original melanin and 2% of MSNP-5 h.
基金Large research project(RGP2/159/45)supported by the Deanship of Research and Graduate Studies at King Khalid University,Saudi Arabia。
文摘The heat transfer between two corresponding plates,disks,and concentric pipes has many applications,including water cleansing and lubrication.Furthermore,TiO_(2)-water-based nanofluids are used widely because it is useful for operating and controlling the temperature,especially in photovoltaic technology and solar panels.Motivated by these applications,the current study is based on the nanoparticle aggregation effect on magnetohydrodynamics(MHD)flow via rotating parallel plates with the chemical reaction.To achieve maximum heat transportation,the Bruggeman model is used to adapt the Maxwell model.Also,melting and thermal radiation effects are considered in the modeling to discuss heat transport.The Runge-Kutta-Fehlberg 4th−5th order method is used to attain numerical solutions.The main focus of this study is to see the thermodynamic behavior considering several aspects of nanoparticle aggregation.The heat transfer rate between the parallel plates is enhanced by improving the thermophoresis,radiation,and Brownian motion parameters.The rise in Schmidt number and chemical reaction rate parameter decreases the concentration distribution.This study will be helpful in enhancing the thermal efficiency of photovoltaic technology in solar plates,water purifying,thermal management of electronic devices,designing effective cooling systems,and other sustainable technologies.
基金supported by the Shanghai Beyond Limits Manufacturing Projectthe National Natural Science Foundation of China(Nos.11502044, U1906233)+2 种基金the Fundamental Research Funds for the Central Universities (No.DUT22JC08)Dalian city supports innovation and entrepreneurship projects for high-level talents (No.2021RD16)Liaoning Province’s Xing Liao Talents Program (No.XLYC2002108)。
文摘Using gas-liquid segmented micromixers to prepare nanoparticles that have a homogeneous particle size, controllable shape, and monodispersity advantages. Although nanoparticle aggregation within a microfluid has been shown to be affected by the shear effect, the shear effect triggering conditions in gasliquid two-phase flow is unclear and the aggregation behavior of nanoparticles under the shear effect is difficult to predict, resulting in uncontrollable physical and chemical properties of nanoparticle aggregates. In this study, a numerical simulation of nanoparticle aggregation in gas-liquid two-phase flow under the shear effect is performed using the CFD-DEM method. Then, the effects of total flow rate,gas-liquid two-phase flow ratio, and particle volume fraction on particle aggregation were analyzed to achieve control of particle aggregation shape and size. Meanwhile, the triggering mechanism of the shear effect and the mechanism of the shear effect on the aggregation of nanoparticles were clarified. The results show that increasing the total flow rate or decreasing the gas-liquid two-phase flow rate ratio can induce the shear effect, which reduces the particle aggregation size and makes the morphology tend to be spherical. Moreover, increasing the particle volume fraction, and total flow rate or decreasing the gas-liquid two-phase flow rate ratio also increases the number of particle collisions and induce interparticle adhesion. Hence, particle adhesion and the shear effect compete with each other and together affect particle aggregation.
基金supported by the State Key Laboratory of Urban Water Resource and Environment(No.2014DX06)the National Natural Science Foundation of China(No.51208142)
文摘The present work aims to ascertain the mechanisms of surfactant（dodecylbenzene sulfonate; DBS） effects on the aggregation behaviors of TiO2 nanoparticles（TiO2-NPs） in natural water samples. Aggregation experiments were conducted at a TiO2-NPs concentration of 10 mg/L in deionized water and in natural water samples via dynamic light scattering and Zeta potential determination. Average attachment efficiency was calculated to compare the aggregation behaviors of nanoparticles in the two aqueous media. Results showed that the effects of DBS on aggregation could be interpreted by both Derjaguin–Landau–Verwey–Overbeek（DLVO） and non-DLVO mechanisms. In natural water samples,aggregation did not occur rapidly and was able to develop slowly under all conditions, and the roles of DBS were obvious at high DBS concentration owing to the impacts of inherent components of natural water samples, such as colloids and natural organic compounds.Future aggregation studies should concentrate on multi-factor, multi-colloidal and dynamic aspects under similar environmental conditions.
基金Sponsered by the State Key Laboratory of Urban Water Resource and Environment(Grant No.2014DX06)the Natural Science Foundation of Heilongjiang Province of China(Grant No.E201154)the Natural Science Foundation of China(Grant No.51208142)
文摘In aqueous environment,organic matters may exert impacts on the aggregation behaviors of titanium dioxide nanoparticles( TiO2-NPs). Owing to the deficiency of studies on the aggregation of TiO2-NPs in the presence of synthetic organic compound,this study used linear alkylbenzene sulfonate( LAS) as a representative to evaluate the effects of TiO2-NPs concentration( 1-10 mg / L),LAS concentration( 0- 1 mg / L),pH( 4- 8)and ionic strength( NaCl,CaCl2; 5- 20 mM) during aggregation of TiO2-NPs suspensions based on the detection of hydrodynamic diameters and electrophoretic mobilities and the calculation of interaction energies.The results showed that the TiO2-NPs in the presence of LAS are more stable than that in the absence of LAS.With the increase of ionic strength,the hydrodynamic diameter of NPs decreases,and the existence of LAS changes the point of zero charge from 5. 4 to a lower value and thus alteres the aggregation behaviors of TiO2-NPs. The present study suggests that the LAS has a significant impact to the transportation and transformation of nanoparticles in aqueous environment.
文摘This work aims to analyze the flow of electrically conducting MWCNTs-nanofluid over a stretching cylinder with the aggregation and non-aggregation effects of nanoparticles. The working fluid comprised a combination of water and ethylene glycol, with volumetric proportions of (50:50) considered. Convective boundary constraints and modified Fourier law are implemented in heat transmission assessment. The mathematical flow model is formulated in the form of PDEs and is transformed into ODEs via similarity transformation. Numerical outcomes will be obtained with the use of the bvp4c technique and will be displayed with the help of graphs and tables. The results show that the surface drag coefficient is enhanced in the case of aggregation of nanoparticles whereas heat transfer rate is enhanced in the non-aggregation effect of nanoparticles. Furthermore, the temperature distribution enhances the increasing values of particle volume fraction in the case of aggregation effects of nanoparticles whereas temperature distribution lowers in the case of non-aggregation effect of nanoparticles. .
