Guanglu Ge

Poly(N-vinyl-2-pyrrolidone) (PVP)-capped dendritic gold nanoparticles by a one-step hydrothermal route and their high SERS effect

Dendritic gold (Au) nanoparticles have been successfully synthesized by the one-step hydrothermal reduction of HAuCl4.4H2O using ammonium formate (AF) as a reducing agent in the presence of PVP. Effects of different reactant concentrations on the morphologies of obtained products have been systematically investigated. On the basis of the morphologies of the products observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), it has been found that an excessive number of AF molecules are the origin of the dendritic Au particles besides PVP as a stabilizer. AF molecules serve not only as a reductant but probably also as a capping reagent. The study implies that the use of two or more capping reagents with different adsorption abilities will be beneficial to the formation of hyperbranched Au nanoparticles. The new finding will have the potential to be extended to the construction of other highly branched noble metal nanoparticles only by one-step synthesis. In addition, as an example, application of the dendritic particles as an active material in surface-enhanced Raman scattering has been investigated by employing 4-aminothiophenol molecules as a probe.

Quantitative study of protein coronas on gold nanoparticles with different surface modifications

AbstractProtein coronas provide the biological identity of nanomaterials in vivo. Here we have used dynamic light scattering (DLS) and transmission electron microscopy (TEM) to investigate the adsorption of serum proteins, including bovine serum albumin (BSA), transferrin (TRF) and fibrinogen (FIB), on gold nanoparticles (AuNPs) with different surface modifications (citrate, thioglycolic acid, cysteine, polyethylene glycol (PEG, Mw = 2 k and 5 k)). AuNPs with PEG(5 k) surface modification showed no protein adsorption. AuNPs with non-PEG surface modifications showed aggregation with FIB. AuNPs with citrate and thioglycolic acid surface modifications showed 6–8 nm thick BSA and TRF coronas (corresponding to monolayer or bilayer proteins), in which the microscopic dissociation constants of BSA and TRF protein coronas are in the range of 10−8 to 10−6 M.

Strongly Coupled Nanorod Vertical Arrays for Plasmonic Sensing

Due to their unique optical properties and facile processability, nanorods of noble metals are promising for highly effective nanoscale optical devices. Specifically, the local electric field enhancement brought about by plasmon coupling between nanorods in an array configuration shows great potential for optical sensing. Recent results demonstrate that vertical arrays of noble metal nanorods, used as substrates for surface enhanced Raman scattering, can achieve the sensitivity levels required for presymptomatic detection. Meanwhile, advancements in controlled fabrication methods can provide nanorod arrays with well-defined structures and properties, which lays the foundation for highly sensitive and reliable sensing. This research news focuses on this rapidly developing field by introducing the mechanisms, characteristics, and preparation methods of nanorod arrays used in plasmonic sensing, along with a perspective for future development and technical requirements.

Aggregated single-walled carbon nanotubes attenuate the behavioural and neurochemical effects of methamphetamine in mice

Methamphetamine (METH) abuse is a serious social and health problem worldwide. At present, there are no effective medications to treat METH addiction. Here, we report that aggregated single-walled carbon nanotubes (aSWNTs) significantly inhibited METH self-administration, METH-induced conditioned place preference and METH- or cue-induced relapse to drug-seeking behaviour in mice. The use of aSWNTs alone did not significantly alter the mesolimbic dopamine system, whereas pretreatment with aSWNTs attenuated METH-induced increases in extracellular dopamine in the ventral striatum. Electrochemical assays suggest that aSWNTs facilitated dopamine oxidation. In addition, aSWNTs attenuated METH-induced increases in tyrosine hydroxylase or synaptic protein expression. These findings suggest that aSWNTs may have therapeutic effects for treatment of METH addiction by oxidation of METH-enhanced extracellular dopamine in the striatum.

Alloyed Crystalline Au-Ag Hollow Nanostructures with High Chemical Stability and Catalytic Performance.

For bimetallic nanoparticles (NPs), the degree of alloying is beginning to be recognized as a significant factor affecting the NP properties. Here, we report an alloyed crystalline Au-Ag hollow nanostructure that exhibits a high catalytic performance, as well as structural and chemical stability. The Au-Ag alloyed hollow and porous nanoshell structures (HPNSs) with different morphologies and subnanoscale crystalline structures were synthesized by adjusting the size of the sacrificial Ag NPs via a galvanic replacement reaction. The catalytic activities of the nanomaterials were evaluated by the model reaction of the catalytic reduction of p-nitrophenol by NaBH4 to p-aminophenol. The experimental results show that the subnanoscale crystalline structure of the Au-Ag bimetallic HPNSs has much greater significance than the apparent morphology does in determining the catalytic ability of the nanostructures. The Au-Ag alloyed HPNSs with better surface crystalline alloying microstructures and open morphologies were found to exhibit much higher catalytic reaction rates and better cyclic usage efficiencies, probably because of the better dispersion of active Au atoms within these materials. These galvanic replacement-synthesized alloyed Au-Ag HPNSs, fabricated by a facile method that avoids Ag degradation, have potential applications in catalysis, nanomedicine (especially in drug/gene delivery and cancer theranostics), and biosensing.

Structure‐Dependent Mitochondrial Dysfunction and Hypoxia Induced with Single‐Walled Carbon Nanotubes

Cytotoxicity of nanomaterials on living systems is known to be affected by their size, shape, surface chemistry, and other physicochemical properties. Exposure to a well-characterized subpopulation of specific nanomaterials is therefore desired to reveal more detailed mechanisms. This study develops scalable density gradient ultracentrifugation sorting of highly dispersed single-walled carbon nanotubes (SWNTs) into four distinct bands based on diameter, aggregation, and structural integrity, with greatly improved efficiency, yield, and reproducibility. With guarantee of high yield and stability of four SWNT fractions, it is possible for the first time, to investigate the structure-dependent bioeffects of four SWNT fractions. it is possible Among these, singly-dispersed integral SWNTs show no significant effects on the mitochondrial functions and hypoxia. The aggregated integral SWNTs show more significant effects on the mitochondrial dysfunction and hypoxia compared to the aggregated SWNTs with poor structure integrity. Then, it is found that the aggregated integral SWNTs induced the irregular mitochondria respiratory and pro-apoptotic proteins activation, while aggregated SWNTs with poor structure integrity greatly enhanced reactive oxygen species (ROS) levels. This work supports the view that control of the distinct structure characteristics of SWNTs helps establish clearer structure-bioeffect correlation and health risk assessment. It is also hoped that these results can help in the design of nanomaterials with higher efficiency and accuracy in subcellular translocation.

Experimental determination and analysis of gold nanorod settlement by differential centrifugal sedimentation

Direct measurement of the sedimentation coefficients of gold nanorods with a controlled shape factor was performed using differential centrifugal sedimentation (DCS). The results serve as a testing ground for various existing models describing non-spherical nanoparticles moving in a centrifugal field based on sphericity and force analysis, and point to further refinement.

In Situ Measurement of Surface Functional Groups on Silica Nanoparticles Using Solvent Relaxation Nuclear Magnetic Resonance

In situ analysis and study on the surface of nanoparticles (NPs) is a key to obtain their important physicochemical properties for the subsequent applications. Of them, most works focus on the qualitative characterization whereas quantitative analysis and measurement on the NPs under their storage and usage conditions is still a challenge. In order to cope with this challenge, solvation relaxation-based nuclear magnetic resonance (NMR) technology has been applied to measure the wet specific surface area and, therefore, determine the number of the bound water molecules on the surface of silica NPs in solution and the hydrophilic groups of various types grafted on the surface of the NPs. By changing the surface functional group on silica particles, the fine distinction for the solvent-particle interaction with different surface group can be quantitatively differentiated by measuring the number of water molecules absorbed on the surface. The results show that the number of the surface hydroxyl, amine, and carboxyl group per nm2 is 4.0, 3.7, and 2.3, respectively, for the silica particles with a diameter of 203 nm. The method reported here is the first attempt to determine in situ the number of bound solvent molecules and any solvophilic groups grafted on nanoparticles.

Experimental and Modeling Studies on the Filtration of SiO2 Nanoparticles Aerosolized from Different Solvents

The filtration performance of a fibrous filter in removing nano-SiO2 aerosols atomized using different solvents including methanol, ethanol, 1-propanol, water, and the ethanol/water mixture has been investigated. Through discrete element method (DEM) simulation and filtration experiments, the efficiency variation caused by the combinative interaction of the particle-filter adhesion and interparticle attraction has been analyzed and verified. The adhesion force between the solvent-coated nanoparticles and the filter is considered as the key factor to influence their initial filtration efficiency and can be balanced by their interparticle interaction. The stronger the adhesion, the higher the initial filtration efficiency. Primary aggregate is formed through the particle-fiber interaction, and further agglomerate is caused by particle migration on the fibers, i.e. secondary aggregate. Hydrogen bonding interaction is considered as the main factor causing interparticle secondary agglomeration, and plenty of OH groups existing in the nano-SiO2 aerosols yielded from alcohol promotes the particle secondary aggregation. As a result, the Brown diffusion capture of the filter is significantly abated, and the as-formed agglomerate is scraped off the filter surface by the alcohol molecules, causing the filtration efficiency decreases. This study highlights the surface affinity properties of nanoaerosols and their balance between particle-particle and particle-fiber interactions in the filtration process.

Synergetic Determination of Thermodynamic and Kinetic Signatures Using Isothermal Titration Calorimetry: A Full-Curve-Fitting Approach

Thermodynamic and kinetic signatures are pivotal information for revealing the binding mechanisms of biomolecules, and they play an indispensable role in drug discovery and optimization. While noncalorimetric methods measure only a part of these signatures, isothermal titration calorimetry (ITC) is considered to have the potential to acquire full signatures in an experiment. However, kinetic parameters are generally difficult to extract from ITC curves, as they are inevitably affected by the instrument-response function and the collateral heat of associated process during titrations. Thus, we herein report the development and validation of a full-curve-fitting method to resolve thermal power curves and to maximize the signal extraction using ITC. This method is then employed to quantify the dilution of an aqueous n-propanol solution and examine the inhibition of carbonic anhydrase by 4-carboxybenzenesulfonamide using a commercial instrument with a long apparent response time of ∼13 s.