Biological and catalytic active nanocomposites of metal nanoparticles (Ag, Au, and Cu) and conductive polymers (polyaniline and polypyrrole) for various applications

A special group of functional materials with advanced features and accordingly promising applications are the nanocomposites of the metal nanoparticles (MNPs) - gold (Au), silver (Ag), and copper (Cu) and intrinsically conductive polymers - polyaniline and polypyrrole [1-7]. Thanks to the characteristics of these MNPs such as tunability of the plasmon resonance through variation of their size, shape, and composition, in combination with polymers, it is possible to create nanocomposites for specific biomedical and catalytic use as a variety of biological/catalytic processes occurring at nanometer scale. These processes are also related to the surface effects of the MNPs, i.e. the reactive (111) crystallographic planes present on their surface, together with the electrical characteristics and morphology of the polymer, as well as the synergistic activity of both components. Biocompatible polymers with good conductivity and electrochemical activity, such as polyaniline or polypyrrole, are good choices for the formation of functional composites with these MNPs, by in-situ polymerization processes. In addition, they protect the MNPs from agglomeration or oxidation and improve their physicochemical characteristics, functions, and variety of applications. The electrocatalytic response of the different prepared nanocomposites for oxygen reduction reaction, and direct borohydride fuel cells, together with their antimicrobial activity, currently investigated in this field in our group, are the subject of the presented work.29th International Symposium on Analytical and Environmental Problems : November 13-14, Szeged, Hungary, 2023

Improvement of Au-poly(N-isopropylacrylamide) hydrogel nanocomposites: Singlelayer vs. bi-layered systems

In recent years, the need for innovative materials has produced remarkable progress in the field of smart materials, with a particular focus on nanocomposite systems containing crosslinked polymer matrices (hydrogels) and metal nanoparticles. Hydrogels have become a crucial class of biomaterials due to their stable 3D porous structures, high fluid absorption capacity, similarity to biological tissues, and biocompatibility. Of particular interest are hydrogels with the ability to respond to various external stimuli (temperature, pH, light etc.), resulting in alterations of their physical and chemical characteristics. Our research focuses on the nanocomposites based on thermosensitive poly(N-isopropylacrylamide) (PNiPAAm) hydrogels and gold nanoparticles (AuNPs), with a unique emphasis on exploring the specific properties of single-layer and bi-layered systems. The insights gained from this comparative study open new possibilities for applications in drug delivery, sensors, and soft robotics. Single-layer systems consisting of active PNiPAAm hydrogel and AuNPs, were created through a combination of radiolytic and chemical procedures. Bi-layered systems feature an active Au-PNiPAAm layer, with the addition of a passive poly(vinyl alcohol) (PVA) hydrogel layer, crosslinked by the combination of freeze-thaw and radiolytic techniques. In both cases, the incorporation of spherical AuNPs within an active layer was confirmed by the presence of a characteristic surface plasmon resonance (SPR), while scanning electron microscopy (SEM) indicated the system's highly porous structure. The physicochemical properties of both single- and bi-layered systems involved the examination of their swelling and deswelling properties, as well as the volume phase transition temperature (VPTT). The incorporation of AuNPs in the PNiPAAm layer led to an increase in both swelling capacity and VPTT. Compression measurements showed that the presence of a passive layer and AuNPs significantly improved mechanical properties of nanocomposites.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Nanostructured Cobalt@Polypyrrole and Cobalt/Gold@Polypyrrole materials: synthesis, optical and structural properties

Nanocomposite materials based on conductive polymers and metal nanoparticles made an appearance as a new class of hybrid materials with considerable potential for application in different fields, from medical and food/wastewater treatments to catalysis and sensors. Besides their low cost and ease of preparation, their optical and mechanical characteristics are tunable, while individual features of each component become more obvious, and new ones appear. In this group of materials, newly, chemically synthesized Cobalt@Polypyrrole (Co@PPy) and Cobalt/Gold@Polypyrrole (Co/Au@PPy) nanocomposites could be classified. With low electrode potential, Co nanoparticles (CoNPs) are unstable, prone to oxidation and agglomeration. For this reason, both nanocomposites were synthesized under argon. Firstly, CoNPs were synthesized in water, by simple reduction of Co2+ by sodium borohydride and in the presence of sodium dodecyl sulfate as a surfactant that will stabilize formed Co nuclei and affect their further growth. After adding pyrrole monomer, the polymerization reaction was initiated by ammonium peroxydisulfate and Au3+ for Co@PPy and Co/Au@PPy, respectively. Together with pyrrole monomer oxidation to final polymer structure by Au3+, these ions are reduced by nitrogen atoms from secondary amino groups in pyrrole units, forming AuNPs incorporated throughout polymer matrix. Conductive form of both nanocomposites, i.e., the presence of bipolarons, was confirmed by UV-Vis and FTIR analysis, while FESEM showed granular morphologies. With both nanocomposites having satisfactory percentage of metals incorporated, it could be expected that such materials could find their place in the field of catalysis, direct borohydride fuel cell, or wastewater treatment, where heavy, toxic metals such As(III) is, represent a great danger for the environment.Twenty-second Annual Conference YUCOMAT : August 30 - September 3, Herceg Novi, 202

Swelling and deswelling kinetics of Au-PNiPAAm hydrogel nanocomposite photoactuators obtained by gamma irradiation

In recent years, photoactuators as a class of smart materials that can produce a reversible mechanical deformation under light stimuli have attracted tremendous interest due to their potential applications in soft robotics, artificial muscles, and smart devices. Currently, the fabrication of photoactuators is mainly based on photothermal actuation mechanisms which include expansion/contraction, molecule sorption/desorption, and phase transition. Thermosensitive hydrogels with gold nanoparticles (AuNPs) are probably the most commonly used active layers that absorb light energy and convert it to thermal energy, causing reversible mechanical deformation such as bending, curling, and spiraling. This work describes hydrogel nanocomposite photoactuators based on AuNPs and thermosensitive poly(N-isopropylacrylamide) (Au-PNiPAAm), obtained by gamma irradiation. The different shapes of AuNPs were incorporated into PNiPAAm hydrogel, nanospheres with radius 5-10 nm and nanorods with aspect ratio 5 (radius 10 nm, length 50 nm). Swelling and deswelling kinetics of Au-PNiPAAm hydrogel nanocomposite photoactuators were investigated in water at 25C and 48C, respectively. All samples showed non-Fickian diffusion (both diffusion and polymer chains relaxation processes control the fluid transport) indicating that incorporation of different shapes of AuNPs into matrices has no influence on the diffusion model. On the other hand, the volume phase transition temperature (VPTT) of photoactuators can be adjusted by the incorporation of different shapes of AuNPs. It has been observed that VPTT decreases from 32.5C for Au nanorods to 30.5C for Au nanospheres, causing a more pronounced photothermal effect in the case of nanospheres.Twenty-second Annual Conference YUCOMAT : August 30 - September 3, Herceg Novi, 202

Surface modification of graphitic carbon nitride with copper nanoparticles

Two different synthetic routes were employed to modify surface of graphitic carbon nitride (g- CN) with copper nanoparticles (CuNPs). Structure, morphology and CuNPs distribution on presynthesized g-CN surface are characterized by FT-IR, XRD and TEM. Results suggested that the simpler method based on mixing of precursors in inert atmosphere and room temperature, resulted in better CuNPs distribution compared to method which used refluxing as a step in synthesis.29th International Symposium on Analytical and Environmental Problems : November 13-14, Szeged, Hungary, 2023

Velocity map imaging VUV angle-resolved photoelectron spectroscopy of isolated silver sulfide nanoparticles

The angle-resolved photoelectron spectroscopy of isolated silver sulfide nanoparticles was carried out by using velocity map imaging technique at the DESIRS beamline of SOLEIL synchrotron facility. The reported spectroscopy results were obtained after interaction of the synchrotron radiation with a polydisperse aerosol produced from aqueous dispersion of silver sulfide particles, approximately 16 nm in diameter. The photoelectron and UV–Vis-NIR absorption spectra were used to estimate the maximum energy of the valance- and the minimum energy of the conduction-band of the nanoparticles. With respect to the vacuum level, the obtained values were found to be 5.5 ± 0.1 eV and 4.5 ± 0.1 eV for the valence band maximum and conduction band minimum, respectively. The dependence of the asymmetry parameter on the electron energy along the silver sulfide valence band showed an onset of inelastic scattering at ~ 1 eV electron kinetic energy

Gamma irradiation-induced synthesis and characterization of bi-layered Au-(PNiPAAm/PVA) hydrogel nanocomposites

RAD 2023 : 11th International Conference on Radiation Natural Sciences, Medicine, Engineering, Technology and Ecology (RAD 2023) 19–23.06.2023; Herceg Novi, Montenegr

Gold nanorod-polyaniline composites: Synthesis and evaluation as anode electrocatalysts for direct borohydride fuel cells

Two gold nanorod-polyaniline (Au-PANI) composites with different contents of Au were prepared by two methods. An ex situ method, in the presence of preformed gold nanorods (AuNRs) and in situ one, when an AuNRs and PANI matrix is produced simultaneously, were used. Both methods were performed in immiscible water/toluene biphasic system as a simple interfacial polymerization process. Optical, structural and morphological characteristics of the formed nanocomposites were identified. It was found that AuNRs are embedded in the conducting emeraldine salt form of PANI. Nanocomposites containing 2.0 and 28.9 wt% of Au were subsequently systematically studied for borohydride oxidation reaction (BOR) for potential application in direct borohydride-peroxide fuel cell (DBPFC). Reaction parameters: number of electrons exchanged, order of reaction and activation energy, were evaluated. Both Au-PANI nanocomposites showed activity for BOR. A laboratory DBPFC was tested reaching specific peak power density of 184 Wg(-1) at 65 degrees C with Au-PANI 1 nanocomposite (containing only 2.0 wt% of Au) as anode