溶剂热法制备银纳米晶

以聚乙烯吡咯烷酮(PVP)作为表面活性剂,利用乙二醇溶剂热法成功制备了银纳米颗粒;利用场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)分析了样品的形貌和晶体结构,并考察了溶剂组成等因素对银纳米颗粒形貌的影响.研究结果表明所得银纳米晶粒径均一,直径约为90nm;增大PVP的加入量会降低产物的粒径,溶剂中水的引入会影响银纳米晶的形貌.     

Preparation of silver nanoparticles in solution from a silver salt by laser irradiation

A new method is proposed for the fabrication of a well-defined size and shape distribution of silver nanoparticles in solution; the method employs direct laser irradiation of an aqueous solution containing a silver salt and a surfactant in the absence of reducing agents.     

Preparation and stabilization of silver nanoparticles by a thermo-responsive pentablock terpolymer

Thermo-reversible silver nanoparticles (Ag-NPs) were prepared by the sodium borohydride reduction of silver nitrate (AgNO₃) in the presence of a pentablock terpolymer, poly(N-isopropylacrylamide)-b-poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PNIPAM₁₅₀-PEO₁₃₆-PPO₄₅-PEO₁₃₆-PNIPAM₁₅₀). The pentablock terpolymer-stabilized silver nanoparticles (Pentablock-S-Ag) were characterized by UV-VIS spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM). At temperatures below lower critical solution temperature (LCST) of Pentablock-S-Ag solutions, the obtained Ag-NPs are well-dispersed with spherical shape, and their sizes mainly depend upon the molar ratios of pentablock terpolymer to AgNO₃; at temperatures above LCST, the size of Ag-NPs decreases and their aggregates are observed due to the collapse and shrinkage of the thermo-responsive PNIPAM and PPO segments. A reversible dispersion-aggregation process upon recyclically changing temperature is also observed.     

Efficient one-pot biosynthesis of silver nanoparticles using Entada spiralis stem powder extraction

Research on Chemical Intermediates - Biosynthesis of noble metal nanoparticles is a vast developing area of research. In the present study, silver nanoparticles (Ag-NPs) are synthesized from...     

Preparation of novel symmetrical bistetrazole-carbazole derivatives through a one-pot Ugi-azide reaction

A series of new symmetrical tetrazole-based carbazole derivatives starting from the initially generated 3,6-diformyl-N-alkylcarbazoles were successfully synthesized through a one-pot Ugi-azide reaction in moderate to high yields. Simplicity, easily accessible chemicals, mild reaction conditions, and fast separation of the products with the formation of bistetrazole-based carbazole derivatives in one step are some advantages of this method. The structure of the products was characterized and confirmed by using spectroscopic techniques such as ¹H NMR, ¹³C NMR, FT-IR, and MS spectroscopy.     

Effective approach to ureas through organocatalyzed one-pot process

An efficient approach to N, N′-unsymmetrically substituted ureas 9 has been developed through the ammonolysis process of N-Boc protected anilines 7 with amines prompted by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). Moreover, a convenient protocol for the synthesis of the symmetric N, N'-substituted ureas 12 by one-pot diammonolysis process of Boc₂O with amines catalyzed by DABCO has also been achieved. With broad substrate scope and mild conditions, these two methods demonstrate practical preparation of both unsymmetrical and symmetrical ureas.     

Preparation and characterization of a novel nanocomposite: silver nanoparticles decorated cerasome

In this study, a novel artificial hybrid vesicle, nano silver particles decorated cerasome were fabricated through sol–gel and self-assemble methods as well as in situ reduction. Samples were characterized in terms of hydrodynamic size and surface morphology via dynamic light scattering as well as scanning and transmission electron microscopies. Analysis through energy dispersive X-ray spectrometer proved the existence of silver particles. Due to the high morphological stability of cerasome, Silver nanoparticles with a size of about 5–10 nm can be deposited on the surface without any stabilizers. The UV spectra revealed a single symmetric extinction peak at 406 nm, confirming the spherical shape of the synthesized silver nanoparticles. Several reducing agents were screened before confirming sodium borohydride (NaBH₄). Comparison of different NaBH₄/lipid ratios (K_{NaBH4/cerasome-forming lipid}) was then carried out in order to ascertain its effect. Investigation of the stability of this hybrid vesicles was carried out, indicating that it can be stored at 4 °C for at least 3 months without any morphological change. Results demonstrated that this hybrid vesicle has excellent morphological stability, which impart it significant potential for various applications such as being an antibacterial material and a radio sensitization agent.     

Preparation of antibacterial polyimide films containing silver nanoparticles

Polyimide/silver composite films were successfully prepared by in situ polymerization. A precursor, AgNO₃ was used as the source of the silver nanoparticles. The structure and morphology of resulting films were characterized by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Consequently, the silver nanoparticles were well dispersed in polyimide matrix. Meanwhile, thermal properties from thermal gravimetric analyses (TGA) and mechanical properties from tensile test which confirmed composites were kept good performance as compared to pure polyimide. In addition, the antimicrobial activity of polyimide/silver composite films against three different bacteria, B. subtilis, S. aureus, and E. coil, illustrated excellent activity. This composite is potential useful as antimicrobial material with good thermal performance in a wide variety of biomedical and general use applications.     

Preparation of silver nanoparticles with controlled particle size

Silver colloids show different colors due to light absorption and scattering in the visible region based on plasmon resonance. The resonance wavelength depends on particle size and shape. Here we report chemical reduction methods for preparation of silver nanoparticles exhibiting multicolor in aqueous solutions. Depending on chemical conditions the obtained nanoparticles are different regarding size and morphology.In order to investigate the relationship between size, stability and color of silver colloids we obtained silver nanoparticles in aqueous solutions using different reducing agents. The effect of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) on stabilization of obtained silver colloids was investigated. We have also studied the effect of silver precursor and its concentration on the formation of stable silver colloids.UV-VIS spectrum for silver colloids contains a strong plasmon band near 410 nm, which confirms silver ions reduction to Ag° in the aqueous phase. The formation of metal silver was also confirmed by powder X-ray diffraction (XRD) analysis. The diameter size of silver nanoparticles was in the range from 5 nm to 100 nm     

Preparation of silver nanoparticles in liquid crystalline systems

Silver nanoparticles preparation and the aggregation stability of the particles was investigated in lamellar liquid crystalline systems. A liquid crystal of HDTABr/pentanol/water was first prepared. The water content was next increased while keeping the mass ratio of HDTABr and pentanol constant. Silver nanoparticles were produced by replacing the aqueous phase by Ag sols of various concentrations (0.5–5×10^–3 mol/l) or by an in situ preparation method, i.e., interlamellar reduction of Ag⁺ ions in the liquid crystalline phase. The stability of the silver nanoparticles was monitored by UV-VIS spectroscopy and TEM. The particle size ranged from 5 to 44 nm. The kinetic of silver nanoparticle aggregation was investigated. The effect of nanoparticles on structural ordering in liquid crystals was studied by XRD measurements and it was established that the lamellar distance (d_L) was only slightly altered. Electronic Publication     

Hexazamacrocycle assisted sensing of silver ion through facile synthesis of silver nanoparticles

The ease of generation of silver nanoparticles by using hexazamacrocycle ligand, L1 is utilized for the visual detection of the presence of silver ions at lower concentrations.     

Preparation of ligand-free TiO2 (anatase) nanoparticles through a nonaqueous process and their surface functionalization

We here present a new method for preparing ligand-free titania nanoparticles, which are easily amenable to surface functionalization in an aqueous environment. The specific advantage of this method is that it combines the advantages of nonaqueous synthetic processes (high crystallinity) to those of a surface functionalization in a water medium, which allows for a wider variety of biofunctional (and nonorganic-soluble) groups to be added on the nanoparticles. In particular, we report on the characterization of the three phases of synthesis, dispersion in water environment and surface functionalization of the nanoparticles, focusing on a qualitative evaluation of the surface adsorption mechanism.     

Preparation and characterization of stable monodisperse silver nanoparticles via photoreduction

Silver nanoparticles were synthesized by UV irradiation of [Ag(NH₃)₂]⁺ aqueous solution using poly(N-vinyl-2-pyrrolidone) (PVP) as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima around 420 nm. It was found that the formation rate of silver nanoparticles from Ag₂O was much quicker than that from AgNO₃, and the absorption intensity increased with PVP concentration as well as irradiation time. The maximum absorption wavelength (λ_max) was blue shift with increasing PVP content until 8 times concentration of [Ag(NH₃)₂]⁺ (wt%). The transmission electron microscopy (TEM) showed the resultant particles were 4–6 nm in size, monodisperse and uniform particle size distribution. X-ray diffraction (XRD) demonstrated that the colloidal nanoparticles were the pure silver. In addition, the silver nanoparticles prepared by the method were stable in aqueous solution over a period of 6 months at room temperature (25 °C).     

Preparation and characterization of silver nanoparticles by chemical reduction method

Silver nanoparticles were prepared by the reduction of AgNO(3) with aniline in dilute aqueous solutions containing cetyltrimethlyammonium bromide, CTAB. Nanoparticles growth was assessed by UV-vis spectroscopy and the average particle size and the size distribution were determined from transmission electron microscopy, TEM. As the reaction proceeds, a typical plasmon absorption band at 390-450nm appears for the silver nanoparticles and the intensities increase with the time. Effects of [aniline], [CTAB] and [Ag(+)] on the particle formation rate were analyzed. The apparent rate constants for the formation of silver nanoparticles first increased until it reached a maximum then decreased with [aniline]. TEM photographs indicate that the silver sol consist of well dispersed agglomerates of spherical shape nanoparticles with particle size range from 10 to 30nm. Aniline concentrations have no significant effect on the shape, size and the size distribution of Ag-nanoparticles. Aniline acts as a reducing as well as adsorbing agent in the preparation of roughly spherical, agglomerated and face-centered-cubic silver nanoparticles.     

Low-temperature metallic alloying of copper and silver nanoparticles with gold nanoparticles through digestive ripening

We describe a remarkable and simple alloying procedure in which noble metal intermetallic nanoparticles are produced in gram quantities via digestive ripening. This process involves mixing of separately prepared colloids of pure Au and pure Ag or Cu particles and then heating in the presence of an alkanethiol under reflux. The result after 1 h is alloy nanoparticles. Particles synthesized according to this procedure were characterized by UV-vis spectroscopy, EDX analysis, and high-resolution electron microscopy, the results of which confirm the formation of alloy particles. The particles of 5.6+/-0.5 nm diameter for Au/Ag and 4.8+/-1.0 nm diameter for Cu/Au undergo facile self-assembly to form 3-D superlattice ordering. It appears that during this digestive ripening process, the organic ligands display an extraordinary chemistry in which atom transfer between atomically pure copper, silver, and gold metal nanoparticles yields monodisperse alloy nanoparticles.     

Transformation of silver nanospheres into triangular nanoplates through a photoinduced process

Triangular silver nanoplates exhibit excellent optical and catalytic properties in many fields, such as catalysts, sensors and bio-medicine. In this paper, triangular nanoplates were generated just in the presence of sodium citrate through a light-induced ripening process, which were converted from spherical silver nanoparticles by reducing silver nitrate with sodium borohydride. By using UV–Vis spectroscopy, particle size analyzer, transmission electron microscopy (TEM) and Ag⁺ concentration analysis, the effects of precursors during the preparation of triangular nanoplates were systematically investigated and the optimal experimental conditions were determined. Based on density functional theory (DFT), the adsorption energies of citrate ion, malate ion and tartronate ion on Ag (1 1 1), (1 1 0) and (1 0 0) were calculated. In addition, theoretical calculations coupled with experimental observations showed that citrate ion as capping agent could more preferentially bind to Ag (1 1 1) and thus blocked Ag (1 1 1) while only allowing extensive growth along the lateral direction. This well explains sodium citrate is an efficient agent in preparing triangular silver nanoplates.     

Preparation and characterization of multi‐walled carbon nanotubes decorated with silver nanoparticles through ultraviolet irradiation reduction

A facile, green and efficient approach was applied to synthesize multi‐walled carbon nanotubes (MWNTs) decorated with silver nanoparticles (MWNT‐Ag) for further potential application. Oxidized MWNTs were decorated with silver nanoparticles (Ag NPs) via a method combining ultraviolet irradiation‐induced reduction and conventional silver mirror reaction without any reducing agent. The obtained product was characterized using various methods. X‐ray diffraction proved that the Ag NPs were synthesized successfully. Moreover, Ag NPs with a diameter of 80 nm, attached onto MWNTs, could be clearly observed in field emission scanning electron microscopy images, which also confirmed Ag NPs. Energy‐dispersive spectroscopy and transmission electron microscopy also indicated the presence of Ag NPs. Furthermore, thermogravimetric analysis was used to measure the content of Ag NPs in MWNT‐Ag, the result indicating that the weight content of Ag NPs was up to 31.88%. UV–visible absorption spectroscopy was adopted to evaluate the dispersion property of MWNT‐Ag. The result illustrated that MWNT‐Ag had a good dispersibility and stability in water. Characterization was also carried out through Fourier transform infrared spectroscopy, Raman spectroscopy and dynamic light scattering analysis.     

Photoinduced one-pot synthesis of hydroxamic acids from aldehydes through in-situ generated silver nanoclusters

Hydroxamic acids have attracted significant attention due to their widespread use in applied chemistry. In this report, a modified Angeli–Rimini method has been achieved via the visible light-mediated catalytic transformation of a variety of heterocyclic, aromatic and aliphatic aldehydes 1a–j to their corresponding hydroxamic acids 2a–j in 81–93% yield. The unique ability of vitamin K₃ as a photoredox catalyst to expedite the development of completely new reaction mechanisms and to enable the construction of challenging carbon–nitrogen bonds has been investigated. It is shown for the first time that the vitamin K₃ and aldehyde are largely responsible for rapid in situ reduction of Ag⁺ ions to catalytic photoluminescent Ag nanoclusters that possess a bandgap energy of 2.87 eV and are less than 2 nm in size. A mechanism for this reaction has been proposed and is supported by UV–Vis, TEM, ESI/MS, FT-IR, ¹H NMR and ¹³C NMR analyses. The investigated method utilizes readily available reagents and produces the hydroxamic acids in high yields without the formation of side products, making it simple, practical and cost-effective.     

Formation and characterization of surfactant stabilized silver nanoparticles: a kinetic study

Kinetic data for the silver nitrate–ascorbic acid redox system in presence of three surfactants (cationic, anionic and nonionic) are reported. Conventional spectrophotometric method was used to monitor the formation of surfactant stabilized nanosize silver particles during the reduction of silver nitrate by ascorbic acid. The size of the particles was determined with the help of transmission electron microscope. It was found that formation of stable perfect transparent silver sol and size of the particles depend upon the nature of the head group of the surfactants, i.e., cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and Triton X-100. The silver nanoparticles are spherical and of uniform particle size, and the average particle size is about 10 and 50 nm, respectively, for SDS and CTAB. For a certain reaction time, i.e., 30 min, the absorbance of reaction mixture first increased until it reached a maximum, then decreased with [ascorbic acid]. The reaction follows a fractional-order kinetics with respect to [ascorbic acid] in presence of CTAB. On the basis of various observations, the most plausible mechanism is proposed for the formation of silver nanoparticles.     

在铜箔上电辅助制备纳米银及其SERS应用研究

在电化学工作站上以铜箔为工作电极,以硝酸银和PVP混合液作为前驱溶液,利用循环伏安法电辅助制备了纳米银,得到在铜箔上紧密均匀分布的纳米银颗粒聚集体作为SERS基底。通过X射线粉末衍射、X射线光电子能谱、扫描电子显微镜等表征手段,对铜箔上负载的银纳米颗粒进行了形貌和成分的表征,探讨了PVP及电辅助方法对纳米银形貌及基底SERS活性的影响。以4-巯基吡啶和罗丹明6G为探针溶液研究了制备基底的SERS活性,同时还对基底的均匀性进行了研究,结果表明所制备的SERS基底具有良好的性能。