Effect Of Metal Nanoparticles Research Articles

Effect of metallic nanoparticles in thin foils for laser ion acceleration

Nanostructured materials having a high absorption coefficient for visible and near-IR wavelengths can be employed to enhance the laser light energy release in micrometric thin foils in order to generate hot non-equilibrium plasmas and to transfer higher ion acceleration energy. Thin polymeric films containing nanometric spheres of metals (Ti, Cu, Ag, and Au) can be employed to be laser irradiated in a high vacuum and to study the consequent plasma ion acceleration process. Infrared laser irradiations at 1010 W cm−2 intensity, 3 ns pulse duration, and 1064 nm wavelength were employed to produce plasma accelerating ions in the backward direction. Measurements have demonstrated that the presence of nanostructures significantly increases the laser absorption effect and consequently the plasma electron temperature and density and the electric field driving the ion acceleration. Target preparation will be extended to submit thin targets to high laser intensity irradiation above 1015 W cm−2, where the effect of ion acceleration should be enhanced.

Accelerated nonradiative electron-excitation energy transfer between molecules in aqueous pools of reverse micelles containing encapsulated silver nanoparticles

The effect of metal nanoparticles on the rate of intermolecular inductive-resonance transfer of electron-excitation energy has been experimentally studied in a system of reverse micelles. The efficiency of the energy transfer has been found to be increased in this system as compared with samples free of metal nanoparticles. A mathematical model that qualitatively agrees with experimental data has been proposed for the process.

Silver-Based Nanoparticles for Surface Plasmon Resonance in Organic Optoelectronics

Organic optoelectronic devices including organic light-emitting diodes (OLEDs) and polymer solar cells (PSCs) have many advantages, including low-cost, mechanical flexibility, and amenability to large-area fabrication based on printing techniques, and have therefore attracted attention as next-generation flexible optoelectronic devices. Although almost 100% internal quantum efficiency of OLEDs has been achieved by using phosphorescent emitters and optimizing device structures, the external quantum efficiency (EQE) of OLEDs is still limited due to poor light extraction. Also, although intensive efforts to develop new conjugated polymers and device architectures have improved power conversion efficiency (PCE) up to 8%–9%, device efficiency must be improved to >10% for commercialization of PSCs. The surface plasmon resonance (SPR) effect of metal nanoparticles (NPs) can be an effective way to improve the extraction of light produced by decay of excitons in the emission layer and by absorption of incident light energy within the active layer. Silver (Ag) NPs are promising plasmonic materials due to a strong SPR peak and light-scattering effect. In this review, different SPR properties of Ag NPs are introduced as a function of size, shape, and surrounding matrix, and review recent progress on application of the SPR effect of AgNPs to OLEDs and PSCs.

Research on photo-thermal properties of plasmonic nanofluid

Localized surface plasmon resonance (LSPR) effects of metal nanoparticles can be used to enhance the photo-thermal properties of nanofluid. The feasibility is verified experimentally in this paper. TiO₂/Ag composite nanoparticles are synthesized by photo- chemical impregnation method. Then, TiO₂/Ag plasmonic nanofluid is prepared by suspending these nanoparticles in base fluid followed by sufficient sonication. The photo-thermal properties of such nanofluid are studied experimentally as well as the effect of concentration. The results show that TiO₂/Ag plasmonic nanofluid exhibits better photo-thermal performance than pure water.

Effect of metal nanoparticles on the photophysical behaviour of dye—silica conjugates

Fluorescein has been covalently entrapped into 120 nm silica beads in order to measure the effect of plasmonic gold nanoparticles, having 25 nm diameter, on the radiative processes of the dye. Two distinct regimes of enhancement and quenching of fluorescein emission have been observed, depending on the concentration of the metal adsorbed on the silica surface and the overlap between the SPR and the fluorescein spectra. At particle concentrations below 5.0 × 10(13) nanoparticles mL(-1), the fluorescence of the dye is enhanced, and this effect is more pronounced when the excitation wavelength matches the maximum of the extinction spectrum of the gold nanoparticles. When the concentration of gold is further increased, quenching occurs and it has been attributed to the SPR shift following the aggregation of the gold colloids on the silica surface. The invariance of the fluorescence lifetimes during the whole process indicates that the mechanism of fluorophore-nanoparticle interaction is mainly based on changes in the absorption efficiency of the organic dye.

Plasmon-enhanced quasi-solid-state dye-sensitized solar cells with metal@Dendron nanoparticles

We have investigated the effects of localized surface plasmons (LSPs) on the performance of quasi-solid-state dye-sensitized solar cells (DSSCs). Ag and Au nanoparticles (NPs) were prepared by photoreduction in the presence of generation 5 polyester hydroxyl acetylene bis(hydroxymethyl)propanoic acid dendrons (Dendron) as a stabilizer. The plasmon-enhanced DSSCs were achieved by incorporating metal@Dendron NPs into TiO2 photoanodes. The presence of dendrons prevents the photoelectrons from recombining on the surface of TiO2 semiconductor and improves the stability of metal NPs. With the addition of Ag@Dendron NPs, the photocurrent and the power conversion efficiency of quasi-solid-state DSSCs increased due to the LSP effect of metal NPs and the barrier effect of dendron, which were confirmed by the increased incident photon-to-photocurrent efficiency and by electrochemical impedance spectroscopy analysis.

Effects of metal nanoparticles on the lateral line system and behaviour in early life stages of zebrafish (Danio rerio)

The unique physicochemistry and potential toxicity of manufactured nanoparticles (NPs) requires innovative approaches for the assessment of toxicity to aquatic organisms. Here, the toxicity of Cu-NPs, Ag-NPs and TiO2-NPs on the lateral line system of free-swimming zebrafish embryos was investigated and compared to appropriate metal salts or bulk material controls. Fish were exposed for 4h at 96-h post-fertilization. Metal salt (CuSO4 and AgNO3) controls reduced the number of functional lateral line neuromasts (LLN) to <5% of unexposed controls, but no effect on LLN was observed for TiO2-NPs or Ag-NPs. Exposure to Cu-NPs caused only a 15% reduction in LLN. Performance of positive rheotaxis was reduced by Cu-NPs, Ag-NPs, and the metal salt controls. The data show that some metal NPs can affect LLN and fish behaviour (rheotaxis) important for survival, and that effects were different from those of comparable metal ion controls.Capsule: We demonstrate that behaviour is a particularly sensitive indicator of metal NP exposure in fish and highlight the interaction between behaviour and external tissue surfaces.

Antiproliferative activity of zinc and metal alloy nanoparticles in transplanted sarcomas.

The effects of zinc and metal alloy (Cu, Zn, and Fe) nanoparticles on transplantation capacity of tumors (mouse sarcoma 37, rat sarcoma 45 and Pliss lymphosarcoma) and the levels of exogenous Zn in tumor and non-tumor tissues of mice were studied. Preincubation (30 min, 37°C) of sarcoma 37 cells with zinc nanoparticles and sarcoma 45 with alloy nanoparticles before transplantation completely prevented the tumor development in animals. Preincubation of Pliss lymphosarcoma cells with nanoparticles led to tumor growth inhibition and prolongation of the animal lifespan. The effect of metal nanoparticles was presumably explained by their local destructive effect on tumor cells. Zinc nanoparticles injected into the tumor concentrated in it after 4 days and were not detected in the adjacent normal tissue. Selective accumulation of metal nanoparticles in tumor tissue and their antiproliferative effect suggested their use as antitumor drugs.

Enhanced optical absorption in organic solar cells using metal nano particles

In this study, for increasing absorption of the active layer in bulk hetero junction (BHJ) organic solar cells (OSCs) we used surface Plasmon effects of metal nano particles (MNPs). We embedded the MNPs inside the active layer and studied the device structure. For shown the results we investigated the model of our structure with Finite Difference Time Domain (FDTD) numerical method and achieved electromagnetic field characters. From the result of this model, drown absorption curve that obviously shown enhancement in light absorption and thus the improving in power convertion efficiency (PCE).

Effect of metal nanoparticles' contact angle on absorption of light in organic solar cell active layer

The enhancement in optical absorption efficiency in solar cells due to incorporation of metal nano-particles (MNPs) may depend on their properties including their contact angles. By appropriately choosing the materials for MNPs and layer on which they are to be deposited, the contact angle may be tuned to maximise optical absorption resulting in higher power conversion efficiency solar cells. In this work, we show by simulation studies that the contact angle of the MNPs with the surface on which they are deposited affects the optical absorption enhancement in an organic solar cell. For poly 3-hexythiophene: phenyl-C61-butyric acid methyl ester blend as the solar cell active layer, simulation studies for incident white light for constant projection area of MNP show that a 0° contact angle gives the highest enhancement in optical absorption. While the enhancement in absorption is observed to be higher for smaller wavelengths for smaller contact angles, the larger contact angle MNPs seems to help absorption in longer wavelengths.

Efficient electrochemical regeneration of nicotinamide cofactors using a cyclopentadienyl-rhodium complex on functionalized indium tin oxide electrodes

Functionalized ITO electrodes are used to regenerate NADH using [Cp*Rh(bpy)(H2O)]2+ (Cp*=pentamethylcyclopentadienyl, bpy=2,2′-bipyridine) electrochemically in a buffer solution. Amino- and mercapto-functionalized electrodes featured higher activity and stability for electrocatalytic generation of NADH than a bare ITO electrode. Effect of metal nanoparticles was also studied on modified ITO electrodes and the addition of platinum nanoparticles even resulted in improved activity. The electrochemical regeneration was somewhat affected in the presence of dioxygen, but not significantly. In addition, a conversion of carbon dioxide was carried out utilizing the electrochemically generated NADH and formate dehydrogenase to produce formic acid.

Natural Occurrence of Potential Fungal Biopesticide Nomuraea Rileyi (Farlow) Samson Associated with Agriculture Fields of Tamil Nadu, India and it s Compatibility with Metallic Nanoparticles

In the present study, natural occurrence of major fungal biopesticide Nomuraea rileyi (Farlow) Samson associated with agricultural field soil in an area around TamilNadu, India was studied adapting culture dependentmethod. Agricultural field soil samples were collected from ten different sites. Soil dilution method was used toisolate N. rileyi. A total of 123 isolates of N.rileyi were obtained. Among the 10 sampling sites, Nomurea rileyi was isolated from 4 sites belonging to Hasthampatty (Salem) Rajakoil (Vellore) Vadavali (Coimbatore), Pullarakottai(Viruthunagar), High frequency of fungal occurrence was recorded in vadavali (60%) followed by Pullarakottai(17%), Hasthampatty (13%,) Rajakoil (10%). Non Nomurae rileyi strains belong to Beauveria sp and Metarhiziumsp were also isolated. Fungal occurrance was highly influenced by soil physico-chemical parameters. Effect ofmetallic nanoparticles such as silver, copper and the respective nanoparticles coated with chitosan on the posttreatment persistance of N. rileyi was also studied.Distinct effcet on the growth of N. rileyi was recorded in copper nanoparticles with high concentration.

Polymer-Based Nanoparticulate Systems as Versatile Agents in the Prognosis and Therapy of Cancer

Polymeric nanoparticulate systems have garnered wide interest as vehicles for intracellular reporter agents and anti-cancer drugs, in anti-cancer gene therapy, and in reducing the adverse toxic effects of metal nanoparticles. These wide ranging applications have been possible due to a favourable blend of polymer properties such as facile chemistry, diverse synthesis options, and amenability towards functionalization. An array of polymeric nanosystems have been developed which exhibit better encapsulation, higher bioavailability, and controlled release of therapeutic agents. In this review, we discuss strategies for synthesizing, tailoring and targeting polymeric nanoparticles, schemes for reducing metal nanoparticle toxicity by using polymers, and recent aspects of internalization and biodistribution of nanoparticulate systems with reference to cancer. We also present the recent clinical status of certain key nanoparticulate anti-cancer drug and gene formulations.

Experimental Study of the Effects of Metal Nanoparticles on Tumor Growth and Bone Marrow Hemopoiesis

Metal (Zn, Cu, Fe) nanoparticles, particularly Zn, induce regression of transplanted sarcoma 37 and increase the percentage of dead and degenerated cells. Antitumor effect of metal nanoparticles was not associated with leukopenia or coarse bone marrow abnormalities, but differential leukocyte and bone marrow counts remained changed.

Effect of metal nanoparticles on energy spectra and optical properties of peripheral light-harvesting LH2 complexes from photosynthetic bacteria

The paper explores the theoretical possibility of affecting optical spectra and the quantum yield of the energy transfer in the peripheral light-harvesting complexes (LH2) from photosynthetic bacteria by placing a metal nanoparticle or a nanoshell nearby. An increased probability of the excitonic transition in the LH2 arises due to the borrowing of the oscillator strength from surface plasmons of the metal particle or the nanoshell. While both absorption and quenching of the excitations increase in the vicinity to a metal nanoparticle, having opposite effects, the total yield of the excitation transfer to reaction centers is shown to grow in the certain range of parameters.

The effect of nanoparticles on gastrointestinal release from modified κ-carrageenan nanocomposite hydrogels

In this article, silver and magnetite nanofillers were synthesized in modified κ-carrageenan hydrogels using the in situ method. The effect of metallic nanoparticles in gastro-intestinal tract (GIT) release of a model drug (methylene blue) has been investigated. The effect of nanoparticles loading and genipin cross-linking on GIT release of nanocomposite is also studied to finally provide the most suitable drug carrier system. In vitro release studies revealed that using metallic nanocomposites hydrogels in GIT studies can improve the drug release in intestine and minimize it in the stomach. It was found that cross-linking and nanofiller loading can significantly improve the targeted release. Therefore, applying metallic nanoparticles seems to be a promising strategy to develop GIT controlled drug delivery.

Formula omitted] measurements in Schiff’s base derivatives: Effect of metal nanoparticles

The third-order nonlinear optical properties of Schiff’s base derivatives and the effect of metal nanoparticles (Ag & Au) on their nonlinear optical response were studied. Colloidal metal nanoparticles were prepared by laser ablation. Z -scan technique with a 7ns Nd:YAG laser pulses at 532 nm were employed for the measurements. The compounds exhibit good optical limiting properties at the wavelength used. The materials used in the present work indicate that these materials are promising candidates for photonics applications.

Theoretical and numerical investigation of the size-dependent optical effects in metal nanoparticles

We further develop the theory of quantum finite-size effects in metallic nanoparticles, which was originally formulated by F. Hache, D. Ricard, and C. Flytzanis [J. Opt. Soc. Am. B 3, 1647 (1986)] and (in a somewhat corrected form) by S. G. Rautian [Sov. Phys. JETP 85, 451 (1997)]. These references consider a metal nanoparticle as a degenerate Fermi gas of conduction electrons in an infinitely high spherical potential well. This model (referred to as the HRFR model below) yields mathematical expressions for the linear and the third-order nonlinear polarizabilities of a nanoparticle in terms of infinite nested series. These series have not been evaluated numerically so far and, in the case of nonlinear polarizability, they cannot be evaluated with the use of conventional computers due to the high computational complexity involved. Rautian has derived a set of remarkable analytical approximations to the series but direct numerical verification of Rautian's approximate formulas remained a formidable challenge. In this work, we derive an expression for the third-order nonlinear polarizability, which is exact within the HRFR model but amenable to numerical implementation. We then evaluate the expressions obtained by us numerically for both linear and nonlinear polarizabilities. We investigate the limits of applicability of Rautian's approximations and find that they are surprisingly accurate in a wide range of physical parameters. We also discuss the limits of small frequencies (comparable to or below the Drude relaxation constant) and of large particle sizes (the bulk limit) and show that these limits are problematic for the HRFR model, irrespective of any additional approximations used. Finally, we compare the HRFR model to the purely classical theory of nonlinear polarization of metal nanoparticles developed by us earlier [G. Y. Panasyuk, J. C. Schotland, and V. A. Markel, Phys. Rev. Lett. 100, 47402 (2008)].

Assessment of toxic effects of metal nanoparticles using biomarkers and in vitro toxicity tests

Assessment of toxic effects of metal nanoparticles using biomarkers and in vitro toxicity tests

Photoluminescence quenching and enhancement of CdSe/PMMA composite on Au colloids

The effects of metallic nanoparticles (NPs) size, excitation wavelength, and fluorescence wavelength on surface plasmon enhanced photoluminescence (PL) have been investigated. The PL of CdSe nanocrystals on Au colloids changes from quenching to enhancement as the size of Au NPs increases from 25 to 45 nm. For the Au NPs larger than 45 nm, the PL enhancement occurs and the enhancement factor is found to be dependent on Au NPs size and excitation wavelength. Besides Au NPs size, the fluorescence wavelength of CdSe nanocrystals is also observed to affect the competition between PL quenching and enhancement.