Small AgNP in the Biopolymer Nanocomposite System

In this work, ultra-small and stable silver nanoparticles (AgNP) on chitosan biopolymer (BP/AgP) were prepared by in situ reduction of the diamminesilver(I) complex ([Ag(NH3)2]+) to create a biostatic membrane system. The small AgNP (3 nm) as a stable source of silver ions, their crystal form, and homogeneous distribution in the whole solid membrane were confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The X-ray photoelectron spectroscopy (XPS) and Auger analysis were applied to investigate the elemental composition, concentration, and chemical state of surface atoms. It was found that ultra-small metallic nanoparticles might form a steady source of silver ions and enhance the biostatic properties of solid membranes. Ultra-small AgNP with disturbed electronic structure and plasmonic properties may generate interaction between amine groups of the biopolymer for improving the homogeneity of the nanometallic layer. In this work, the significant differences between the typical way (deposition of ex-situ-prepared AgNP) and the proposed in-situ synthesis approach were determined. The improved thermal stability (by thermogravimetry and differential scanning calorimetry (TG/DSC) analysis) for BP/AgP was observed and explained by the presence of the protective layer of a low-molecular silver phase. Finally, the antibacterial activity of the BP/AgP nanocomposite was tested using selected bacteria biofilms. The grafted membrane showed clear inhibition properties by destruction and multiple damages of bacteria cells. The possible mechanisms of biocidal activity were discussed, and the investigation of the AgNP influence on the bacteria body was illustrated by AFM measurements. The results obtained concluded that the biopolymer membrane properties were significantly improved by the integration with ultra-small Ag nanoparticles, which added value to its applications as a biostatic membrane system for filtration and separation issues

Microstructure characterization of noble metal-silica nanocomposites

The presence of highly dispersed metal particles on solid supports with well-defined microstructure is important in the field of functional materials, active catalysts as well as bionanomaterials for medical applications. Noble metal nanostructures, in particular silver, palladium, and platinum nanoparticles were formed from ammine complexes ([Pt(NH₃)₄]Cl₂, [Ag(NH₃)₂]OH, and [Pd(NH₃)₄]Cl₂) and supported on high ordered mesoporous silica (SBA-15) and aluminosilica matrix. In this work, the distribution, composition and crystal structure of supported noble metal nanoparticles were determined and characterized. Finally the stability of incorporated nanostructures was confirmed. The microstructures of the obtained samples were analyzed by high resolution transmission electron microscopy. Obtained results indicated that developed procedures of synthesis and modification of mesoporous ordered silica or their derivate by proposed nanostructures are effective and allow to obtain new nanocomposites and nanocatalysts in repeatable and controlled way

Actual challenges, opportunities, and perspectives of composite materials

The development of technology is associated with a strong need for changes in the design and manufacture of new types of materials. Monolithic materials such as ceramics or metals have become insufficient for the needs of the modern market. The combination of several types of materials in one system turned out to be the right solution. Composite materials as multi-phase materials show improved properties compared with individual structural elements and can give the opportunity to design systems with enhanced specific characteristics.The presented work provides a review of actual literature dedicated to composite materials. In this work, the basic terminology, the division of composite systems, the most commonly used methods for composites preparation as well as physicochemical characteristics and potential applications of these types of matter were presented

Preparation and Structural Properties of Bimetallic Noble Metals Nanoparticles in SBA-15 Systems

New noble bimetallic materials composed of platinum/silver, platinum/palladium and palladium/silver arrangements of nanoparticles supported on mesoporous ordered silica support were obtained and characterized. Ammine complexes of noble metals ([Pt(NH 3 ) 4 ]Cl 2 ), [Ag(NH 3 ) 2 ]OH and ([Pd(NH 3 ) 4 ]Cl 2 )) were used as nanoparticles sources. The selected ammine complexes of noble metals were proven to be an easy solution for obtaining good quality materials in comparison with other sources. Bimetallic materials were synthesized by traditional impregnation technique, making the proposed procedure simple and reproducible. Our studies demonstrated that there are significant differences between types of materials and thermal stability of their metal precursor and their decomposition mechanisms. The X-ray diffraction results showed that the obtained metal crystallites exhibited different sizes depending on the kind of noble metal, as indicated by significant differences in intensity and width of diffraction profiles for metal phases. Such difference in sizes of individual components causes different kinds of interaction between metal nanoparticle and solid support. The binding energy of reactants depends on the particle size. This difference was characterized by X-ray photoelectron spectroscopy measurements. The obtained materials were characterized by various techniques suitable for surface characterization with particular emphasis on high-resolution transmission electron microscopy

Synthesis of new mesostructured cellular foams (MCFs) with NaY zeolite and their application to sorption of thorium ions

The paper presents the new way of preparation of MCF foams with NaY zeolite. Significant changes in the amount of micro and mesopores in relation to the amount of NaY zeolite and 1,3,5-trimethylbenzene (TMB) added during the synthesis was observed. It suggests the possibility of controlling the micro/mesopores ratio by applying the proposed method. Environmental aspects of using new MCF/NaY foams is related to the adsorption of thorium ions (Th+4). The term of “MCF/NaY materials” refers to the general name of the material without referring to the content and state of zeolite. The obtained materials were highly effective in relation to Th+4. The adsorption capacity was greater when the number of micropores was lower. The dependence of adsorption capacity of Th+4 ions on aluminum atoms content was also confirmed

Silver nanoparticles deposited on pyrogenic silica solids: Preparation and textural properties

Silver-based nanomaterials and composites are important components in materials science and engineering due to the reactivity of silver nanophase based on exceptional surface effects. Ag-doped SiO 2 nanocomposites were synthesized by wet impregnation procedure of aminopropyl-functionalized silica materials with submicrometer structure. Aminopropyl-functionalized pyrogenic silicon dioxide with amount of amino groups established as half and close to full monolayer was used to immobilize the nanosilver phase obtained from ammoniacal silver complex as a noble metal precursor. Pyrogenic silicon dioxide as an inexpensive nanostructured material with useful properties including adsorptive affinity for noble metal ions and organic macromolecules was applied as a support for diamminesilver(I) ions and finally for silver nanoparticles. In the present study, the effect of amino-functionalization and silver nanoparticles deposition was monitored by investigation of the textural properties and thermal stability of obtained nanocomposites. The properties of the nanocomposites were investigated by transmission electron microscopy, nitrogen adsorption–desorption isotherms, and thermal analysis (thermogravimetry/differential scanning calorimetry)

Silver Nanoparticles on Chitosan/Silica Nanofibers: Characterization and Antibacterial Activity

A simple, low-cost, and reproducible method for creating materials with even silver nanoparticles (AgNP) dispersion was established. Chitosan nanofibers with silica phase (CS/silica) were synthesized by an electrospinning technique to obtain highly porous 3D nanofiber scaffolds. Silver nanoparticles in the form of a well-dispersed metallic phase were synthesized in an external preparation step and embedded in the CS/silica nanofibers by deposition for obtaining chitosan nanofibers with silica phase decorated by silver nanoparticles (Ag/CS/silica). The antibacterial activity of investigated materials was tested using Gram-positive and Gram-negative bacteria. The results were compared with the properties of the nanocomposite without silver nanoparticles and a colloidal solution of AgNP. The minimum inhibitory concentration (MIC) of obtained AgNP against Staphylococcus aureus (S. aureus) ATCC25923 and Escherichia coli (E. coli) ATCC25922 was determined. The physicochemical characterization of Ag/CS/silica nanofibers using various analytical techniques, as well as the applicability of these techniques in the characterization of this type of nanocomposite, is presented. The resulting Ag/CS/silica nanocomposites (Ag/CS/silica nanofibers) were characterized by small angle X-ray scattering (SAXS), X-ray diffraction (XRD), and atomic force microscopy (AFM). The morphology of the AgNP in solution, both initial and extracted from composite, the properties of composites, the size, and crystallinity of the nanoparticles, and the characteristics of the chitosan fibers were determined by electron microscopy (SEM and TEM)