Preparation of pH-responsive silver nanoparticles by RAFT polymerization

Silver nanoparticles were prepared by chemical reduction of AgNO₃ in the presence of the PDMAEMA-b-PPA, which was synthesized by the reversible addition-fragmentation transfer technique. The formation of the silver nanoparticles was determined by the transmission electron microscopy (TEM) images and UV–Vis absorption spectra. The average size of the silver nanoparticles was shown to 11.4 nm. Particularly, the pH-responsive property of the silver nanoparticle was further observed. It was characterized by the zate potential, the UV–Vis spectra, and TEM images. The results show that the pH-responsive property is attributed to the aggregate of the silver nanoparticles as a function of pH. The characteristic is expected to apply in the nanoscale optical biosensor and biomaterials.     

化学还原法制备纳米银粒子及其表征

采用化学还原法, 通过一系列条件实验,借助紫外-可见分光光度计(UV-vis)得到最佳实验条件,在最佳实验条件下制得紫黑色溶胶,在40℃下真空干燥3h,获纳米银粉.制备的纳米银粉用X射线衍射仪(XRD)和透射电镜(TEM)分析表明,其粒径大小分布范围窄,形状为单一球形,平均粒径为18nm.     

Preparation of silver nanoparticles by photo-reduction for surface-enhanced Raman scattering

A substrate for surface-enhanced Raman scattering (SERS) has been developed. Based on the surface-catalyzed reduction of Ag⁺ by citrate on the silver nanoparticles surface under light irradiation, small silver seeds on a quartz slide can be enlarged. The optical properties and characteristics of the silver films have been investigated by ultraviolet-visible spectroscopy, scan electron microscope and atomic force microscopy (AFM). The results indicate that the particle size and shape are different at different reduction time. At the first 3 h, some triangular and hexagonal nanoparticles formed; with the reduction proceeding, the shape of the silver particles became irregular and the size became larger. The silver films obtained are very suitable as SERS active substrate. The relationship between SERS intensity and the reduction time has been investigated for 1,4-bis[2-(4-pyridyl)ethenyl]-benzene molecule adsorbed on the silver film. The SERS intensity reached a maximum at 8 h reduction. The AFM measurements indicate that roughness features with an average size of 100 nm are present on the surface, which yielded the strongest SERS signal. Pyridine was used as a probe molecule to investigate the enhancement factor (EF) of the silver films. According to the formalism of Tian and co-workers, the EF of the silver films is estimated to be 3.4 × 10⁵. The silver film that can remain active for more than 50 days would seem to be suitable for various analytical applications.     

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization

Seeded emulsion polymerization was used to prepare magnetic polymeric composite nanoparticles (MPCNPs) with the aim to successfully encapsulate magnetite particles and to improve particle size distribution (PSD). Microscopical morphology and number-average diameter of hydrophilic magnetite particles (HMPs), magnetic seed latex nanoparticles (MSLNPs) and MPCNPs were observed and analyzed by transmission electron microscope (TEM). Weight-average diameter and PSD of MSLNPs and MPCNPs were also analyzed by TEM. Magnetic properties of MPCNPs were investigated by Vibrating Sample Magnetometry (VSM). The results showed that the encapsulation of magnetite particles was not complete by conventional emulsion polymerization but very successful by seeded emulsion polymerization, the resulted MPCNPs were nanoparticles with much narrower PSD than that of MSLNPs, and exhibited superparamagnetism and possessed a certain level of magnetic response.     

Preparation and characterization of dendritic silver nanoparticles

Dendritic silver nanoparticles have been prepared by a soft solution technique from the aqueous solution of silver nitrate and poly (vinyl pyrrolidone) (PVP) in the presence of ethanol used as a reducing agent. The resultant silver nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive analyses of X-ray (EDX), and UV-Visible absorption spectroscopy. It was found that the well-defined dendritic silver nanoparticles which had the length 0.5–1 m and the width of 100–200 nm.     

电纺丝技术制备银纳米粒子/聚合物复合纳米纤维

银/聚合物纳米复合材料是一种典型的聚合物基复合材料,本文综述了运用电纺丝技术制备银纳米粒子,聚合物复合纳米纤维的最新研究进展.     

Preparation and size control of silver nanoparticles by a thermal method

In this letter we report that stable silver nanoparticles can be facilely prepared directly from an amine-containing polyelectrolyte/AgNO₃ aqueous solution without the additional step of introducing other reducing agents and protective agents through a thermal process. More importantly, the size of nanoparticles thus formed can be controlled by the initial molar ratio of polyelectrolyte to Ag.     

Preparation of silver nanoparticles via a non-template method

Silver nanoparticles have been prepared by a non-template method. Silver nitrate can be easily decomposed into silver nanosized materials. Small nanoparticles (less than 2 nm) can be formed in aqueous solution. Larger silver particles of about 100 nm can be formed in ethanol solution. By rationally adjusting the experimental conditions we finally obtain silver particles of about 20 nm with a relatively narrow distribution in ethanol solution. Differing from the previous reports, we find that silver nanoparticles can be formed by direct decomposition of AgNO₃ under UV light irradiation. No catalyst like TiO₂ is needed at all. We believe that it is a further step to precede the preparation of silver nanometer sized materials.     

扩散控制无皂乳液聚合法制备纳米聚合物微球

在不添加任何乳化剂的条件下,将甲基丙烯酸(MAA)和苯乙烯(St)单体进行无皂乳液聚合,制备纳米聚合物微球。由于采用的搅拌速率较低,单体相和水相呈现层状分布,聚合反应速率由单体扩散速率控制。跟传统的动力学控制乳液聚合法相比,扩散控制所得产物粒径较小,最小可达35nm,且乳液稳定性较好。采用傅里叶变换红外光谱仪(FTIR)、动态激光光散射(DLS)、核磁(1 HNMR)、扫描电镜(SEM)对其进行表征。并研究了反应温度、引发剂用量、单体摩尔配比对乳液稳定性和微球粒径的影响,发现反应温度在80℃,引发剂的占单体质量百分数为25%,单体摩尔配比1:2.5的时候乳液稳定,微球最小粒径35nm,57.7%的粒子小于100nm。     

Preparation of silver nanoparticles dispersed in polyacrylonitrile nanofiber film spun by electrospinning

Ag nanoparticles dispersed in polyacrylonitrile (PAN) nanofiber film spun by electrospinning were in situ prepared by reduction of silver ions in N₂H₅OH aqueous solution. The Ag/PAN nanocomposite film was characterized by UV absorption spectroscopy, transmission electron microscopy (TEM) and surface-enhanced Raman scattering (SERS) spectroscopy. UV spectrum and TEM image show that silver nanoparticles with average diameter of 10 nm were obtained and dispersed homogeneously in PAN nanofibers. SERS spectrum indicates that the structure of PAN has been changed after Ag nanoparticles are dispersed in PAN.     

Preparation of thermosensitive gold nanoparticles by plasma pretreatment and UV grafted polymerization

This work is to develop an easy method of plasma treatment and graft polymerization to prepare thermosensitive gold nanoparticles. Gold nanoparticles (Nano-Au) were reduced by trisodium citrate combined with hydrogen tetrachloroaurate(III) tetrahydrate (chloroauric acid) and modified with 11-mercaptoundecanoic acid (MUA) by the self-assembly monolayers (SAM). The surface graft polymerization of N-isopropylacrylamide (NIPAAm) was carried out by two steps, using O₂ plasma pretreatment of the surface on MUA SAM modified Nano-Au to form the peroxide groups on Nano-Au(MUA), and then subsequently using UV light to induce grafting with thermosensitive polymer. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to direct investigation of the particle size and morphology in situ. The diameters of the gold nanoparticles measured from the TEM images are in good agreement with data measured at room temperature which is about 15 nm. The thermosensitive gold nanoparticles were characterized by chemical structure of surface (ESCA) and Fourier-transform infrared spectroscopy (FTIR). ESCA result suggests that plasma treatments can be employed to generate peroxides on the Nano-Au(MUA) for the subsequent UV graft polymerization of PNIPAAm.     

纳米纤维素/银纳米粒子的制备和表征

以纳米纤维素(NCC)为分散剂,硼氢化钠为还原剂还原硝酸银,化学还原法制备纳米纤维素/银纳米粒子。m(Ag)/m(NCC)=5%制备的纳米纤维素/银纳米粒子,X射线衍射分析结果表明,纳米纤维素/银纳米粒子中NCC和银纳米粒子相互混合并未改变各自的晶型,纳米纤维素/银纳米粒子中银纳米粒子的晶粒尺寸为11.87nm,与透射电子显微镜(TEM)所测银纳米粒子直径(10nm)相近;热重分析结果表明,纳米纤维素/银纳米粒子的热稳定性较纳米纤维素稍有下降。透射电子显微镜(TEM)分析、紫外光谱分析、固含量分析、机理分析和抑菌活性分析结果表明,m(Ag)/m(NCC)=3%时制备的纳米纤维素/银纳米粒子对大肠杆菌和金黄色葡萄球菌均有抑制作用,且银纳米粒子在纳米纤维素/银纳米粒子中分散较均匀。     

壳聚糖修饰银纳米颗粒的制备及抗菌性能研究

采用液相化学还原法,以壳聚糖为修饰剂,硼氢化钠为还原剂,制备了壳聚糖修饰银纳米颗粒(chitosan-Ag NPs)。通过X射线粉末衍射仪、透射电子显微镜、傅立叶变换红外光谱仪等对所制备样品的结构和形貌进行了表征。结果表明,所制备纳米颗粒具有面心立方Ag的晶型结构,壳聚糖通过氨基和羟基中的N、O原子与Ag+的化学键合作用修饰在纳米颗粒表面,起到了限制颗粒粒径长大和防止其团聚的作用。采用肉汤连续稀释法检测了样品对大肠杆菌和金黄色葡萄球菌的抑菌杀菌性能,结果表明chitosan-Ag NPs具有优异的抗菌性,抗菌性能受到粒径大小的影响。     

Effect of silver nanoparticles content on the various properties of nanocomposite hydrogels by in situ polymerization

A series of nanocomposite hydrogels (APEAg series gels) were prepared from acrylic acid, poly(ethylene glycol) methyl ether acrylate, and silver nanoparticles through in situ polymerization by UV irradiation. The effect of the content of silver nanoparticle on the properties of the nanocomposite hydrogels was investigated. Results showed that, with increasing of the content of the silver nanoparticle in the hydrogels, the crosslinking density and shear modulus of the hydrogel were not obviously changed, the electrical conductivities of the nanocomposite hydrogels increased, and their initial rate of Escherichia coli inactivation significantly increased, but their adhesive force only slightly decreased. These materials can be assessed as promising bioadhesive patch or wound-dressing material or electrical massage patch.     

Preparation and antibacterial properties of hybrid-zirconia films with silver nanoparticles

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix–polyether glycol was studied. AgNps of 4–6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconia–polyether glycol mixtures during the ageing procedure. Atomic force microscopy (AFM) of the modified hybrid film showed a homogenous distribution of 20–80 nm diameter AgNps, indicating agglomeration of these structures during film modification; such agglomerations were greater when increasing the dosage of the colloidal system. The AgNps-hybrid films showed higher antimicrobial activity against Gram-positive bacteria than for Gram-negative bacteria. Hybrid films prepared with dioctyl sodium sulfosuccinate (AOT) stabilized AgNps presented enhanced antibacterial activity compared to that obtained through the addition of a high AgNO₃ concentration (0.3 wt%).     

Preparation of linoleic acid-capped silver nanoparticles and their antimicrobial effect

Silver nanoparticles have been prepared through the chemical reduction of silver ions by ethanol using linoleic acid as a stabilising agent. This colloidal solution shows an absorption band in the visible range with an absorption peak at 421 nm. The peaks in the X-ray diffraction (XRD) pattern matches well with the standard values of the face-centred-cubic form of metallic silver. Transmission Electron Microscope (TEM) micrograph shows a nearly uniform distribution of the particles with an average size of 8 nm. This linoleic acid-capped silver nanoparticles show antimicrobial activity against Escherichia coli and Staphylococcus aureus.     

负载纳米银颗粒的纳米纤维膜的制备与表征

采用一步还原法和螯合法制备Ag/PAN纳米纤维膜。采用SEM,UV,XRD,FT-IR傅里叶变换红外光谱仪对该纤维形貌,银粒子晶型、尺寸、官能团进行表征。得知两种方法都可制备出嵌有(或附着)纳米银颗粒的PAN纳米纤维膜,银粒子的粒径可以达10nm,且经过比较,Ag/PAN膜经过还原处理后,表面Ag粒子的含量更高,分布更均匀。     

Microwave-assisted one-step patterning of aqueous colloidal silver

A new approach of utilizing microwave to pattern gradient concentric silver nanoparticle ring structures has been presented. The width and height of a single ring and the space between adjacent rings can be adjusted by changing the silver colloidal concentration and the microwave output power. By simply enhancing the ambient vapour pressure to the saturated value during microwave-assisted evaporation, sub-100?nm rings can be deposited in between adjacent micro-rings over a distance of millimetres. Combined with microwave sintering, this approach can also create conductive silver tracks in a single step, showing huge potential in fabricating micro-?and nano-electronic devices in an ultra-fast and cost-effective fashion.     

Tuning photoluminescence of ZnS nanoparticles by silver

We report the results of investigation of the interaction of silver with presynthesized ZnS nanoparticles (NPs) that was stabilized by cetyl trimethyl ammonium bromide (CTAB). The photoluminescence properties of ZnS NPs were followed in the presence of Ag⁺ ions, Ag NPs and by the synthesis of Ag@ZnS core-shell nanoparticles. We observed that CTAB stabilized ZnS NPs emitted broadly in the region from 350–450 nm, when excited by 309 nm light. In the presence of Ag⁺ ions the emission peak intensity up to 400 nm was reduced, while two new and stronger peaks at 430 nm and 550 nm appeared. Similar results were obtained when Ag NPs solution was added to ZnS solution. However, when Ag@ZnS NPs were synthesized, the emission in the 350–450 nm region was much weaker in comparison to that at 540 nm, which itself appeared at a wavelength shorter than that of Ag⁺ ion added ZnS NPs. The observations have been explained by the presence of interstitial sulfur and Zn²⁺, especially near the surface of the nanocrystals and their interaction with various forms of silver. In addition, our observations suggest that Ag⁺ ions diffuse into the lattice of the preformed ZnS NPs just like the formation of Ag⁺ doped ZnS NPs and thus changes the emission characteristics. We also have pursued similar experiments with addition of Mn²⁺ ions to ZnS and observed similar results of emission characteristics of Mn²⁺ doped ZnS NPs. We expect that results would stimulate further research interests in the development of fluoremetric metal ion sensors based on interaction with quantum dots.     

Preparation of silver nanoparticles stabilized on the surface of polystyrene microspheres

Silver nanoparticles stabilized on the surface of polystyrene microspheres have been prepared by reducing silver ammine with formaldehyde, without surface activation of the microspheres. The size distributions of the nanoparticles have been obtained, and the optical absorption spectra of the synthesized nanomaterials have been measured.