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The determination of the physical and chemical properties of small nanoparticles plays a fundamental role in homogeneous and heterogeneous catalysis since a large number of the surface atoms of these nanoparticles can be exposed to chemical reactions, as well as in chemisorption, solid state physics, laser physics, crystal growth, epitaxy and surface science in general as most recent experimental and theoretical investigations have been disclosed. An empirical many-body Potential Energy Function (PEF) incorporating two-plus three-body atomistic potential derived by fitting experimental data pertaining to bulk Iridium has been applied to study the structural stability and energetics of Iridium nanoparticles of Ir_n ($n=3$–13). A constant temperature Molecular Dynamics (MD) technique is employed in the simulations. It is found that the energetically most stable structures of Iridium nanoparticles are in three-dimensional distorted compact forms close to symmetric geometries with the MD technique. The theoretical predictions are compared to the available theoretical and experimental literature data for binding energies, bond lengths and the most stable nanocluster geometry.

A theory for the averaged optical characteristics of an ensemble of metal nanoparticles with different shapes has been developed. The theory is applicable both for the nanoparticle size at which the optical conductivity of the particle is a scalar and for the nanoparticle size at which the optical conductivity should be considered as a tensor. The averaged characteristics were obtained taking into account the influence of nanoparticle shape on the depolarization coefficient and the components of the optical conductivity tensor. The dependences of magnetic absorption by a spheroidal metal nanoparticle on the ratio between its curvature radii and the angle between the spheroid symmetry axis and the magnetic field vector were derived and theoretically considered. An original variant of the distribution function for nanoparticle shapes, which is based on the combined application of the Gaussian and “hat” functions, was proposed and analyzed.

In this paper, we systemically and numerically investigate the effects of three types of Nanoparticles on the efficiency of solar cells. Finite Difference Time Domain method has been implemented to compute the absorption spectra in such proposed solar cell structure. High efficiency has been achieved by optimizing the nanoparticles layer by tuning the fraction of nanoparticles on the host layer.

It is argued that in the long wavelength limit of electromagnetic, far infrared, field optical response of an ultrafine metal particle threaded by uniform magnetic field can be properly modeled by equations of semiclassical electron theory in terms of the surface inertial-wave-like oscillations of free electrons driven by Lorentz restoring force. The detailed calculation of the frequency of size-independent gyromagnetic plasmon resonances computed as a function of multipole degree of electron cyclotron oscillations is presented. This spectrum is derived in juxtaposition with the canonical Mie's spectral formula for the surface plasmon resonances caused by the Coulomb-force-driven plasma oscillations of conduction electrons.

The optical properties of nanoscopic arrays of metal particles are dominated by plasmon resonances and electromagnetic interaction between the particles. We use electron-beam lithography to prepare arrays of noncentrosymmetric gold particles and study their linear and second-order nonlinear optical properties. By varying the orientation of the particles in a fixed lattice, we observe shifts in the polarized linear extinction spectra. The second-harmonic generation efficiencies of the two types of samples differ by up to 60%. The results show that the properties of the samples are sensitive to the smallest details of their structure.

We have prepared nanocomplexes composed of silver or gold nanoparticles as a core and merocyanine or phthalocyanine as a shell portion by the co-reprecipitation method. From their absorption spectra, the core metal nanoparticles seemed to interact electronically with the shell layer of organic compounds in the nanocomplexes to give different electronic states from their original states. The morphology of their nanocomplexes was observed by electron microscopies.

The distribution details of strongly-localized fields in metal nanostructures are important for strong interaction with the locally-varying non-linearity. Using gold nanodimers with nanogaps, we demonstrate that field localization alone is insufficient to drive a strong second-order response. Instead, polarization conversion of the local fundamental field combines with its asymmetric distribution along the dimer perimeter to yield strong responses. Strongly-localized fields may also favor higher-multipole (magnetic-dipole and electric-quadrupole) contributions to their nonlinear response. We show that the polarization-dependent interference of multipole sources in second-harmonic generation from gold nanoparticles allows the separation of their relative contributions.

Nonlinear plasmonic metasurfaces have recently attracted considerable interest, due to their potential for enabling nanoscale nonlinear optics. Here, we review the current progress in this topic while paying special attention to existing challenges. In order to limit our scope, we concentrate on nonlinear metasurfaces utilizing inter-particle and lattice effects and focus on metasurfaces operating close to visible and near-infrared frequencies. We will also critically discuss the short and longer term prospects of nonlinear metasurfaces to start rivaling traditional nonlinear materials in applications.

High fluence low energy negative ion implantation has been used to synthesize embedded metal nanoclusters of Au, Ag and Sb in silica glass. The Au- and Ag-implanted samples showed peaks, corresponding to surface plasmon resonance (SPR) in the optical absorption (OA) spectra, confirming the formation of metallic nanoparticles in the matrix. No SPR peak was observed in case of Sb-implanted samples which is attributed to the absence of pure metallic precipitates which could be detected in the OA spectrum. Low frequency Raman scattering (LFRS) measurements also confirm this. Cross-sectional transmission electron microscopy has been used to infer about the size distribution of the nanoparticles. Sequential implantations of Au and Ag or Au and Sb have been found to result in SPR peaks at locations in between those for nanoparticles of the constituent atoms, indicating the formation of alloy nanoparticles in the system. In case of the Au + Ag system, Rutherford backscattering spectrometry has been used to infer about the composition of the nanoparticles in terms of the concentrations of the metallic constituents. A direct, one-to-one correspondence between the SPR peak position and composition has been observed.

Eco-friendlybiosynthesis of silver nanoparticles (Ag NPs) and gold (Au NPs) nanoparticles by using Punica granatum and C. reticulata extracts were synthesized efficiently. Ag and Au NPs with sizes 8–10 nm and 30–40 nm were successfully synthesized and extracts serve as capping agents. Forming of NPs was confirmed through UV-visible spectra, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) studies. The effect of NPs on the luminescence of Eu(TTFA)₃ and Sm(TTFA)₃ complexes was investigated. Luminescence intensities of the complexes were enhanced several times in the presence of silver and get quenched due to reabsorption of Au NPs. The nonlinear optical properties of NPs were calculated using open aperture Z-scan and degenerate four-wave mixing in the femtosecond region. The toxicity and antimicrobial activities of Ag and Au NPs were studied.

In this paper, we report herein for the first time that a stop solution should be used to terminate the metal nanoparticles (MNPs) aggregation reactions especially salt-induced ones to increase the repeatability of the assays. It was found that hydrophobic surfactants have the ability to slow down the aggregation process of MNPs and can be applied as stop solution for aggregation-based colorimetric assays. This trick provides accurate and well-repeatable signals since the aggregation of the nanoparticles is a dynamic process and capturing signal in a predetermined time is difficult.

Significant efforts in the field of colloidal semiconductor particles have been dedicated to the fabrication and study of hybrid metal–semiconductor nanoheterostructures, where the incorporation of the metal moiety may potentially enhance and/or expand existing applications of semiconductor nanoparticles. Many of these metal–semiconductor nanostructured constructs exhibit physical properties not found in either of their metal or semiconductor components, providing many opportunities for further investigation into interface and coupling effects between the two materials. We review some of the key research endeavors in this area, focusing mainly on the synthesis of the materials and the characterization of the various metal–semiconductor constructs, and highlighting some of the unique applications that have emerged from these efforts.

Noble metal nanoparticles exhibit strong surface plasmon resonance (SPR) and have been utilized in many chemical, biological and electronic applications. Recent advances on metal-enhanced optical properties demonstrated that the quantum yield and photo-stability of the fluorophores can be significantly enhanced when they are in the proximity of the metal surface, that will benefit many fluorescence-based applications. In this review article we first discuss the fundamental concepts of metal-enhanced optical properties and the recent achievements of metal-enhanced fluorescence of organic fluorophores and quantum dots, as well as metal-enhanced phosphorescence of organic molecules and upconversion nanoparticles that have long life times. Finally, we present recent applications of metal-enhanced optical properties in biosensing and bioassays, photodynamic therapy and optoelectronics.

Copper, nickel and cobalt metals and oxides needle-like shape nanoclusters have been synthesized successfully by chemical reduction in solution without using a surfactant. XRD analyses showed that copper and nickel metals could be synthesized in a short time period by a microwave irradiation (MWI) — assisted step wise reduction of metal ions in basic solution using hydrazine as a reducing agent whereas cobalt was mainly precipitated in the form of either hydroxide or oxide. TEM images showed that the size of needle-like shape nanoclusters varying from about 5 nm to few hundred nanometers length. On the other hand, copper and cobalt showed high catalytic activity toward CO oxidation than that of nickel. The mechanism of catalytic oxidation reactions over unsupported metals and oxides are also discussed.

The paper was retracted as the authors have submitted the same manuscript to two completely different journals, which is seriously academic fraud and against academic ethics.

The yolk-shell Fe₃O₄-polyaniline for decoration of Pd-Ni nanoparticles (yolk-shell Fe₃O₄-PANI/Pd-Ni) were synthesized and used as a new electrocatalyst for oxidation of formic acid. The yolk-shell Fe₃O₄-PANI/Pd-Ni catalyst provided superior catalyst performance for formic acid oxidation in H₂SO₄ aqueous solution. These yolk-shell Fe₃O₄-PANI/Pd-Ni catalysts were found to be more resistant to deactivation in the oxidation of formic acid than yolk-shell Fe₃O₄-PANI/Pd and Pd/C and to consistently show better long-term performances. The enhanced catalytic performance may arise from the unique structure and surface properties of the yolk-shell Fe₃O₄-PANI and bi-functional effect, which process extraordinary promotional effect on Pd catalyst.

Cancer remains a significant global health burden, claiming countless lives annually and incurring substantial direct and indirect economic costs. Despite advancements in therapeutic modalities, conventional cancer treatments, including chemotherapy, radiotherapy and surgery, are often hampered by limitations such as insufficient efficacy, dose-dependent side effects, high costs and patient tolerability. This has spurred extensive research into novel therapeutic approaches for this life-threatening disease. Metal nanoparticles (MNPs) have emerged as promising tools in cancer therapy due to their unique physicochemical properties spanning the past two decades. Owing to their size similarity to biological molecules, MNPs possess the inherent ability to penetrate cellular barriers, making them ideal carriers for targeted drug delivery. These multifunctional nanoplatforms offer distinct advantages over conventional therapeutics by enabling targeted delivery of anticancer agents to specific tumor sites, thereby enhancing therapeutic efficacy and minimizing systemic side effects. Photodynamic therapy and sonodynamic therapy represent particularly promising strategies that leverage MNPs for cancer treatment. This review delves into the potential applications of MNPs in modulating the tumor microenvironment, paving the way for the exploration of this vast and rapidly evolving field of nanomedicine.

Highly monodispersed palladium (Pd) nanoparticles have been successfully incorporated inside the mesopores of a metal–organic framework (MOF), MIL-101, without deposition of Pd nanoparticles on the external surfaces of framework by using the "double solvents" method, in which cyclohexane is used as a hydrophobic solvent to disperse the mesoporous MOF and an aqueous solution of Pd precursor is used as a hydrophilic solvent to fill the mesopores. The resulting Pd@MIL-101 composite is highly catalytically active for the reduction of 4-nitrophenol (4-NPh) by sodium borohydride (NaBH₄). The observed excellent catalytic performances are attributed to the small Pd nanoparticles within the pores of MIL-101.

The aim of this review is to provide an up-to-date overview of nanoparticles developed for use as photothermal therapy agents (PTT) over the past five years. The main emphasis is on nanoparticles that absorb near infrared (NIR) light for PTT of cancer. Mild hyperthermia, including drug delivery, versus thermal ablation is also discussed. Recent advances in the synthesis of highly anisotropic novel metal nanoparticles for PTT are described. New metals and metal oxide complexes, as well as the use of quantum dots for PTT and as imaging agents are newer areas of development that are explained. This review also highlights current progress in the development of carbon nanoparticles, including reduced graphene oxide for both thermal ablation as well as drug delivery. The review culminates in the recent use electrically conductive polymer nanoparticles for hyperthermia. The advantages and unique features of these contemporary nanoparticles being used for PTT are highlighted. The goal of the present work is to describe the recent evolution of nanoparticles for NIR stimulated PTT, and highlight the innovations and future directions.

Study of nanoparticles has attracted the immense attention of researchers because of their wide applications in the medicine, chemical industries, and biotechnology. This paper highlights that plants and microbes can be a source of bio-compounds in nanoparticle synthesis in place of toxic chemicals. As this is an environmentally friendly approach following the principles of green synthesis which is cheap and is not toxic. Both sources provide antioxidant, anticancer, and antimicrobial properties which hold great importance in the manufacturing of NPs. This review aims to bring together the diversity of synthesized metallic nanoparticles mediated by plant extracts, fungi, algae, bacteria and yeasts. All the mentioned bio-resources contain biomolecule which includes protein and enzyme which serves the twin action of both reduction and capping of the synthesized nanoparticles. The synthesized NPs are characterized by using UV-visible spectrometry, FT-IR, XRD, TEM, SEM and EDX. Also, the biomedical application of the synthesized NPs is explored in the treatment of cancer.