Bacterial synthesized metal and metal salt nanoparticles in biomedical applications: An up and coming approach

In the present scenario, metal nanoparticles have elicited a great deal of interest in biomedical applications because of their unique properties and antimicrobial potentials. Over the past few years, the green nanotechnology has materialized as a momentous approach for the synthesis and fabrication of noble metal salt and metal nanoparticles. The green route synthesis exploits diverse reducing and stabilizing agents from bacterial resources for the successful synthesis of metal nanoparticles. This review mainly focuses on the biosynthesis of the most commonly studied metal and metal salt nanoparticles such as gold, silver, platinum, palladium, copper, cadmium, titanium oxide, zinc oxide, zinc sulphate, cadmium sulphide and many more. These noble nanoparticles can be exploited in pharmaceutical industry as antimicrobial and anti-biofilm agents, targeted delivery of anticancer drugs, biosensors, etc.     

Toxicological Effects of Metal Nanoparticles Employed in Biomedicine: Biocompatibility,Clinical Trials,and Future Perspective

Metal nanoparticles play a crucial role in the medical industry due to its desirable properties such as antimicrobial activity, anti-cancer property, and its application in disease diagnostics. These properties enable the nanoparticles to be used as efficient medical devices for various treatments as well as drug delivery systems. Despite all the positives, metal nanoparticles are known for causing toxicity in the living system. The toxicological effects of metal nanoparticles are due to their size, surface*e coating, and the dose administered. Therefore, it is important to study the toxic effects of these nanoparticles before they are used as medical devices for various treatments. This review focuses on the five major metal nanoparticles used in the medical field, namely; silver, gold, iron oxide, zinc oxide, and titanium dioxide nanoparticles. The non-exhaustive review consists of an introduction to the toxicological effects of these nanoparticles, the biocompatibility, and the current and future clinical perspective on metal nanoparticles.     

Pd/ZnO和Ag/ZnO复合纳米粒子的制备、表征及光催化活性

 用焙烧前驱物碱式碳酸锌的方法制备了ZnO纳米粒子，采用光还原沉积贵金属的方法制备了Pd／ZnO和Ag／ZnO复合纳米粒子，并利用ICP，XRD，TEM和XPS等测试技术对样品进行了表征，初步探讨了贵金属在ZnO纳米粒子表面形成原子簇的原因．以光催化氧化气相正庚烷为模型反应，考察了样品的光催化活性以及贵金属沉积量对催化剂活性的影响．结果表明：沉积适量的贵金属，ZnO纳米粒子光催化剂的活性大幅度提高．同时，深入探讨了表面沉积贵金属的ZnO纳米粒子光催化剂活性有所提高的内在原因．     

聚苯胺/贵金属复合纳米材料的可控合成及催化应用

导电高分子/贵金属复合纳米材料因其在催化、传感、表面增强拉曼、光热治疗等诸多领域的应用前景而受到广泛关注.本文主要介绍我们课题组近年来利用可控合成策略制备的负载型和包埋型两种结构聚苯胺/贵金属复合纳米材料,以及利用复合纳米材料的结构和功能特性,对其在多相催化领域的应用、结构与催化性能之间构效关系的探索.     

Catalysis with transition metal nanoparticles in colloidal solution: nanoparticle shape dependence and stability

While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape of the colloidal nanocatalyst on the catalytic activity as well as the effect of the catalytic process on the shape and size of the colloidal transition metal nanocatalysts and their recycling potential. These studies provide important clues on the mechanism of the reactions we studied and also can be very useful in the process of designing better catalysts in the future.     

Colloidal Metal Nanocatalysts: Synthesis,Characterization, and Catalytic Applications

Metal nanoparticles are key materials in heterogeneous catalysis due to their high catalytic activity and selectivity to the desired product. Accordingly, they are playing a pivotal role in most heterogeneous catalytic reactions that are steeply growing with the development of a colloidal synthetic protocol that enables fine control of size, shape, morphology and composition of metal nanoparticles at an atomic level. These colloidal metal nanoparticles can be dispersed on a rigid support such as mesoporous silica, metal oxide and zeolite, which utilizes metal nanoparticles as model heterogeneous catalysts in industrially important processes involving hydrogenation/dehydrogenation, isomerization and cracking. In this review article, we highlight the recent progress on general colloidal synthetic routes with technological advances in characterization tools that enable the atomic-scale observation of metal nanoparticles. Structure-dependent contributions on the control of product selectivity and turnover rate are also discussed by combining advanced ex situ and in situ surface characterization tools that can monitor the structural change of metal nanocatalysts as well as the evolution of reaction intermediates under the reaction conditions.     

Surface chemistry of quantum-sized metal nanoparticles under light illumination

Size reduction of metal nanoparticles increases the exposure of metal surfaces significantly, favoring heterogeneous chemistry at the surface of the nanoparticles. The optical properties of metal nanoparticles, such as light absorption, also exhibit a strong dependence on their size. It is expected that there will be strong coupling of light absorption and surface chemistry when the metal nanoparticles are small enough. For instance, metal nanoparticles with sizes in the range of 2–10 nm exhibit both surface plasmon resonances, which can efficiently produce high-energy hot electrons near the surface of the nanoparticles under light illumination, and the Coulomb blockade effect, which favors electron transfer from the metal nanoparticles to the surface adsorbates. The synergy of efficient hot electron generation and electron transfer on the surface of small metal nanoparticles leads to double-faced effects: (i) surface (adsorption) chemistry influences optical absorption in the metal nanoparticles, and (ii) optical absorption in the metal nanoparticles promotes (or inhibits) surface adsorption and heterogeneous chemistry. This review article focuses on the discussion of typical quantum phenomena in metal nanoparticles of 2–10 nm in size, which are referred to as “quantum-sized metal nanoparticles”. Both theoretical and experimental examples and results are summarized to highlight the strong correlations between the optical absorption and surface chemistry for quantum-sized metal nanoparticles of various compositions. A comprehensive understanding of these correlations may shed light on achieving high-efficiency photocatalysis and photonics.

Size reduction of metal nanoparticles increases the exposure of metal surfaces significantly, favoring heterogeneous photochemistry at the surface of the nanoparticles.     

金属纳米颗粒制备中的还原剂与修饰剂*

金属纳米颗粒由于其独特的光学、电学、化学性质以及各种潜在的应用价值,受到不少研究人员的广泛关注。实现金属纳米粒子尺寸、形貌可控,改善粒子分散性和稳定性,提高产率及纯度已成为具有挑战性的研究课题,不断发展和完善金属纳米粒子的合成方法则显得尤为重要。本文总结了目前制备金属纳米材料的几种化学方法：化学试剂还原法、电化学还原法、辐射还原法等,分类介绍了化学试剂还原法中常用的无机、有机还原剂,以及含氮、磷、羧基、巯基小分子有机化合物以及高分子聚合物等修饰剂并重点总结了其还原和修饰机理。     

Why gold nanoparticles are more precious than pretty gold: noble metal surface plasmon resonance and its enhancement of the radiative and nonradiative properties of nanocrystals of different shapes

This tutorial review presents an introduction to the field of noble metal nanoparticles and their current applications. The origin of the surface plasmon resonance and synthesis procedures are described. A number of applications are presented that take advantage of the electromagnetic field enhancement of the radiative properties of noble metal nanoparticles resulting from the surface plasmon oscillations.     

In vitro Toxicological Study of Metal Oxides Nanoparticles on Oxidation of Succinate in Krebs Cycle and Their Resultant Effect in Metabolic Pathways

In vitro study to evaluate toxic effects of metal oxides nanoparticles on energy producing cycle was conducted. In this study oxidation of sodium succinate in aqueous solution was investigated by using potassium ferricyanide as an oxidizing agent. Kinetic measurements were carried out on kinetic mode of spectrophotometer at λ_max 420 nm. Effect of different metal oxides (MgO and CaO) nanoparticles was observed on the oxidation of succinate at 25 ± 0.5 °C. These metal oxides nanoparticles were prepared by hydrothermal method and their characterization were done by using FTIR, TGA, SEM‐EDX, TEM and XRD. Kinetic results indicated that these nanoparticles inhibit the conversion of succinate into fumerate. The inhibition is directly dependent on particle size of the nanoparticles and it was observed that particle size is inversely related to the oxidation rate of succinate. It was concluded at the end that elevated concentrations of metal oxides nanoparticles can severely affect the Krebs cycle by inhibiting succinate oxidation and lead to various metabolic disorders.     

Reactions of nanoparticles inside a polyethylene matrix: Reduction of lead(II) and mercury(II) oxides by supercritical isopropanol

Methods were developed for manufacturing of isolated nanoparticles of lead(II) and mercury(II) oxides produced by the thermal decomposition of metal compounds in a solution-melt of low-density polyethylene (LDPE) in mineral oil. The PbO and HgO nanoparticles stabilized in the LDPE matrix were characterized using X-ray powder diffraction and transmission electron microscopy (TEM). The metal oxides in the polyethylene matrix were reacted with a supercritical fluid of isopropanol (SCF i-PrOH). The PbO in the nanoparticles was reduced to the metal as a result of the reaction with SCF i-PrOH. When SCF i-PrOH was reacted with the HgO nanoparticles stabilized in the LDPE matrix, the oxide was also reduced to the metal. TEM showed that the nanoparticles were conserved after their reaction with SCF i-PrOH.     

Textural manipulation of mesoporous materials for hosting of metallic nanocatalysts

The preparation and stabilization of nanoparticles are becoming very crucial issues in the field of so-called "nanocatalysis". Recent developments in supramolecular self-assembled porous materials have opened a new way to get nanoparticles hosted in the channels of such materials. In this paper, a new approach towards monodisperse and thermally stable metal nanoparticles by confining them in ordered mesoporous materials is presented, and three aspects are illustrated. Firstly, the recent progress in the functional control of mesoporous materials will be briefly introduced, and the rational tuning of the textures, pore size, and pore length is demonstrated by controlling supramolecular self-assembly behavior. A novel synthesis of short-pore mesoporous materials is emphasized for their easy mass transfer in both biomolecule absorption and the facile assembly of metal nanocomposites within their pore channels. In the second part, the different routes for encapsulating monodisperse nanoparticles inside channels of porous materials are discussed, which mainly includes the ion-exchange/conventional incipient wetness impregnation, in situ encapsulation routes, organometallic methodologies, and surface functionalization schemes. A facile in situ autoreduction route is highlighted to get monodisperse metal nanoparticles with tunable sizes inside the channels of mesoporous silica. Finally, confinement of mesoporous materials is demonstrated to improve the thermal stability of monodisperse metal nanoparticles catalysts and a special emphasis will be focused on the stabilization of the metal nanoparticles with a low Tammann temperature. Several catalytic reactions concerning the catalysis of nanoparticles will be presented. These uniform nanochannels, which confine monodisperse and stable metal nanoparticles catalysts, are of great importance in the exploration of size-dependent catalytic chemistry and further understanding the nature of catalytic reactions.     

纳米粒子的制备及其在打印印刷领域的应用

本文简要介绍了几类纳米粒子的制备及其在打印印刷领域的应用.包括无机纳米粒子复合材料用于绿色打印制版、聚合物乳胶纳米粒子用于喷墨打印制备光子晶体、金属纳米粒子用于印刷电路以及纳米材料用于3D打印,并展望了其发展前景.     

Rigid nanoscopic containers for highly dispersed, stable metal and bimetal nanoparticles with both size and site control

We demonstrate a novel strategy for the preparation of mesoporous silica-supported, highly dispersed, stable metal and bimetal nanoparticles with both size and site control. The supporting mesoporous silica, functionalized by polyaminoamine (PAMAM) dendrimers, is prepared by repeated Michael addition with methyl acrylates (MA) and amidation reaction with ethylenediamine (EDA), by using aminopropyl-functionalized mesoporous silica as the starting material. The encapsulation of metal nanoparticles within the dendrimer-propagated mesoporous silica is achieved by the chemical reduction of metal-salt-impregnated dendrimer-mesoporous silica by using aqueous hydrazine. The site control of the metal or bimetal nanoparticles is accomplished by the localization of inter- or intradendrimeric nanoparticles within the mesoporous silica tunnels. The size of the encapsulated nanoparticles is controlled by their confinement to the nanocavity of the dendrimer and the mesopore. For Cu and Pd, particles locate at the lining of mesoporous tunnels, and have diameters of less than 2.0 nm. For Pd/Pt, particles locate at the middle of mesoporous tunnels and have diameters in the range of 2.0-4.2 nm. The Pd and Pd/Pt nanoparticles are very stable in air, whereas the Cu nanoparticles are stable only in an inert atmosphere.     

Synthesis and reactivity of metal-containing monomers 72. Monomeric and polymeric metal acetylenecarboxylates and their nanocomposite products: synthesis,structures, and properties

Methods for the synthesis of a number of transition metal acetylenedicarboxylates were developed. The ways and conditions for their polymerization were studied. The polymerization of metal acetylenedicarboxylates was accompanied by the formation of polyconjugated chains. Controlled thermolysis of metal acetylenedicarboxylates yielded matrix-stabilized metal nanoparticles. The microstructures and magnetic properties of the nanocomposites obtained were examined.     

基于贵金属纳米颗粒生长的比色传感研究进展

近年来,作为颜色标记和信号发生器的贵金属纳米粒子由于其简单性和实用性而被广泛用于比色测定和传感的研究当中。本文综述了近十年基于贵金属纳米粒子生长的比色传感器策略和应用的最新进展,总结了基于贵金属纳米颗粒生长的单色及多色传感器的传感原理、分类及前沿应用,探索了其比色传感的信号产生、分类和放大机制。由于贵金属纳米粒子在不同尺寸、距离、形状、成分等基底上的生长会产生不同的LSPR共振峰以及显著的传感信号变化,我们详细讨论了贵金属纳米粒子在金纳米棒等晶种基底上生长的比色传感。最后,我们对目前该比色传感面临的挑战和未来前景进行了展望。     

Effect of the metal nature on hemostatic activity of water-soluble gold and silver nanocomposites

The hemostatic activity of polymeric gold and silver nanocomposites depends on their kinetic stability caused by the interaction of the ligand with nanoparticles. The properties of the nanoparticles are determined by the metal nature.     

The complexes of macromolecules and metal nanoparticles: pseudo-template synthesis and behavior

Metal sols composed of metal nanoparticles (1 - 10 nm in diameter) protected with polymer molecules may be regarded as dispersions of polymer-metal complexes formed due to cooperative non-covalent (e.g., hydrophobic, coulombic) interaction of polymer chains with the surface of metal nanoparticles. The sols are commonly prepared by reducing of metal ions in solutions of appropriate polymers. The interactions between macromolecules and nanoparticles are reversible. In the case of long polymer chains and minute particles, the equilibrium constant of the reaction exponentially depends on the surface area of the particle. The probability of mutual “recognition” (complex formation) of growing particle and a macromolecule rapidly increases from practically zero to practically unity in narrow interval of the particle's diameters. The recognition is followed with the shadowing of the particles and the stop of their growths. Such kind of processes was termed “pseudo-template”. In frame of the concept of pseudo-template processes can be estimated: (1) the conditions at which sol particles of desirable size can be prepared, (2) the influence of temperature, polymer concentration, nanoparticles size, and other conditions on the stability of polymer - particle complex having been prepared, and (3) the conditions at which stable sol does not exist and can not be prepared at all. The interactions between metal nanoparticles and macromolecules are highly selective regard to the structure of polymer chains. The property can be effectively used for the control the size characteristics of metal nanoparticles (in course of their formation) and the stability of metal sols. The selectivity provides high conversions in catalytic chemical modification reactions in which a macromolecule is the substrate and a component of the catalyst in the same time. As an example, the hydrolysis of lactame groups in monomer unites of poly(N-vinyl pyrrolidone) catalyzed with copper sols is discussed.     

Ligand-stabilized metal nanoparticles in organic solvent

This critical review reports the fundamental behavior of metal nanoparticles in different organic solvents, i.e., metal organosol. An overview on metal organosol and then their smart synthetic approaches, characterization, and potential applications in the fields of catalysis and spectroscopy with special emphasis on SERS are embodied. Aspects of organosol fabrication, stabilization, morphology control, growth mechanisms, and physical properties as mono- and bimetallic nanoparticles are discussed. The article inspires the repetitive usage of metal nanoparticles as stable deliverable organic and molecular compounds.