Spherical Metal Nanoparticles Research Articles

Morphological and Structural Characterization of (Pt, Au, and Ag) Nanoparticle/Zn-MOF-74 Composites.

Metallic nanoparticles (NPs) were decorated onto Zn-MOF-74 crystals by photoreducing different metal precursors (Pt, Au, and Ag) using ultraviolet (UV) light in an aqueous solution with different metal concentrations without using additional stabilizers. X-ray diffraction revealed the three-dimensional structural integrity and crystallinity conservation of Zn-MOF-74 crystals during the UV decoration process. Raman spectroscopy showed a minor rearrangement in the structure of the Zn-MOF-74 crystal surface after NP decoration. X-ray photoelectron spectroscopy confirmed the metal oxidation states of Zn and NPs. High-resolution transmission electron microscopy images proved the surface decoration of Zn-MOF-74 crystals with spherical metallic NPs with diameters between 2.4 and 9.8 nm.

Q-factor of plasmonic resonances and field enhancement in the vicinity of spherical metallic nanoparticles

Q-factor of plasmonic resonances and field enhancement in the vicinity of spherical metallic nanoparticles

Influence of environmental conditions on the morphological evolution of bismuth oxide nanostructures via pulsed laser ablation in liquids

Bismuth oxide nanomaterials are increasingly recognized for their promising electronic and optical properties, particularly in electrochemical and biomedical applications. This study demonstrates that various bismuth oxide nanostructures can be synthesized through pulsed laser ablation in liquids (PLAL) by adjusting the concentration of dissolved gases from ambient conditions. Structural and compositional analyses were performed using x-ray diffraction, Raman spectroscopy, FTIR spectroscopy, and morphological investigations were conducted using atomic force microscopy and transmission electron microscopy. Our findings indicate that factors such as dissolved gases, laser fluence, and nanoparticle aging are crucial in determining the final structure and composition of the resulting nanomaterial. The phases observed ranged from spherical metallic bismuth nanoparticles to monoclinic bismuth oxide nanowire bundles, and orthorhombic bismuth carbonate oxide nanosheets. Dissolved gases are shown to influence not only the primary particles formed immediately after ablation, but also significantly impact the aging process of the colloid as well. Additionally, fluence plays an important role in the production of reactive oxygen species, thereby influencing the reactive pathways experienced by the ablated material and its subsequent formation into nanostructures. A notable result, emphasizing the significance of factors such as liquid environment and fluence when performing PLAL on reactive targets like bismuth, is seen in high fluence (20 J/cm2) samples under ambient conditions. These samples initially display an amalgamation of α-Bi2O3 nanowire bundles and carbonate nanosheets, which upon aging, transition to predominantly bismuth oxide nanowire bundles. This contrasts with samples produced in a saturated CO2 environment where bismuth carbonate nanosheets remain highly stable in the colloid.

Phonon heat removal from metal nanoparticles and dynamics of nanoparticle cooling at low temperatures

The theoretical analysis of the energy relaxation of an electron–phonon system of metal nanoparticles embedded in a dielectric matrix is usually based on semiphenomenological dynamic equations for electron and phonon temperatures (two-temperature model), which does not take into account the nonthermal nature of the phonon distribution function. In this work, we use a microscopic model that describes the dynamics of the electron–phonon system of metal nanorods and metal spherical nanoparticles in terms of the kinetic equation for the phonon distribution function. We focus on the size effect in the transfer of heat from a nanoparticle to a dielectric matrix. If the dimensions of the nanoparticle are much larger than the phonon-electron mean free path, then the heat transfer is determined by the properties of the interface between the nanoparticle and the matrix. In the opposite case, heat removal is determined solely by the parameters of the electron–phonon interaction in a metal nanoparticle. The dynamics of cooling of nanoparticles is also considered and the dependence of the electron temperature on time is obtained.

Facile microwave-assisted preparation of Fe3O4 nanoparticles supported on carbonized cellulose nanocrystals derived from sugarcane bagasse

Microwave energy is an efficient form of energy used to speed up the synthesis of nanoparticles. Herein, we report the use of an unmodified domestic microwave oven to prepare magnetic spherical Fe3O4 (magnetite) nanoparticles (IONPs) supported on carbonized cellulose nanocrystals, forming a nanocomposite, in an expeditious and facile one-step reaction. This was achieved using the readily available precursors of FeCl3 as an iron source, and sugarcane bagasse, using activated charcoal as a microwave absorber. The nanocomposite was characterized using Raman spectroscopy which suggested a degree of crystallinity based on a G/D ratio of 1.25. The morphology of the Fe3O4/carbonized cellulose nanocrystal nanocomposite was characterized as spherical metallic nanoparticles supported on carbonized cellulose nanocrystals using Transmission electron microscopy (TEM), SEM, and EDX, while the identity of the Fe3O4 nanoparticles was confirmed with powder XRD.Graphical

Rearrangement of the Conformations of Polyampholitic Macromolecules on the Surface of a Charged Spherical Metal Nanoparticle in an Alternating Electric Field: Molecular Dynamic Simulation

Rearrangement of the Conformations of Polyampholitic Macromolecules on the Surface of a Charged Spherical Metal Nanoparticle in an Alternating Electric Field: Molecular Dynamic Simulation

Rearrangement of the Conformations of Polyampholitic Macromolecules on the Surface of a Charged Spherical Metal Nanoparticle in an Alternating Electric Field: Molecular Dynamic Simulation

The rearrangement of the conformational structure of polyampholytic polypeptides on the surface of a charged spherical gold nanoparticle with its polarity intermittently changing over time was studied using molecular dynamics modeling. The angular distributions of the polypeptide atoms, as well as the radial distributions of the macrochain atomic density in the equatorial region of the nanoparticle with differentiation according to the types of links, were calculated. The polyampholyte shell acquired an annular shape, and the resulting macromolecular ring was located around the charged nanoparticle perpendicularly to the vector of the external electric field strength. With an increase in the charge of the nanoparticle, the ring belt was ordered according to the types of macrochain links, forming concentric annular layers. The diameter of the macromolecular ring depended on the law of distribution of charged units in the macrochain. At elevated temperatures the annular macromolecular ring was deformed at the moments of the highest polarization of the nanoparticle.

3D-printed liquid metal polymer composites as NIR-responsive 4D printing soft robot

4D printing combines 3D printing with nanomaterials to create shape-morphing materials that exhibit stimuli-responsive functionalities. In this study, reversible addition-fragmentation chain transfer polymerization agents grafted onto liquid metal nanoparticles are successfully employed in ultraviolet light-mediated stereolithographic 3D printing and near-infrared light-responsive 4D printing. Spherical liquid metal nanoparticles are directly prepared in 3D-printed resins via a one-pot approach, providing a simple and efficient strategy for fabricating liquid metal-polymer composites. Unlike rigid nanoparticles, the soft and liquid nature of nanoparticles reduces glass transition temperature, tensile stress, and modulus of 3D-printed materials. This approach enables the photothermal-induced 4D printing of composites, as demonstrated by the programmed shape memory of 3D-printed composites rapidly recovering to their original shape in 60 s under light irradiation. This work provides a perspective on the use of liquid metal-polymer composites in 4D printing, showcasing their potential for application in the field of soft robots.

Pump-probe response and four-wave mixing in quantum dot exciton-biexciton – metal nanoparticle hybrid

We investigate theoretically the pump-probe response and the four-wave mixing spectrum in a hybrid system composed of a semiconductor quantum dot coupled to a spherical metal nanoparticle including both ground to exciton and exciton-biexciton transitions. We use a density matrix methodology for the calculation of the absorption/gain, dispersion and four-wave mixing spectra and examine their spectral characteristics, for different interparticle distances and under different pump field detuning conditions with respect to the one-photon and the two-photon resonance transitions. We also analyze the form of the spectra using a metastate theory, a description based on the coupling between the excitonic and the plasmonic transitions, while the dressed-state picture is applied in order to predict the positions at which the spectral resonances arise on the spectra.

Electronic and light absorption properties of metal adsorbed In2Se3 monolayer

With its excellent optical and electrical characteristics, two-dimensional (2D) In2Se3 has a lot of potential uses in flexible electronics, photodetectors, and phase-change memory, and so on. In this study, we have systematically investigated the electronic structure and light absorption properties of a metal atom adsorbed monolayers of In2Se3 using density functional theory. The findings indicate that the most stable sites of different metal adsorbed In2Se3 monolayer materials are different. All metal atoms adsorbed In2Se3 (M-In2Se3) systems have good stability. After the adsorption of metal atoms on all M-In2Se3 systems, it can be seen by their energy band structures that all systems exhibit metallic behavior. It is illustrated that the adsorption of metal atoms can modulate the change of In2Se3 material from semiconductor to metal. Similarly, the densities of states plots show the metallic nature of the M-In2Se3 system structure and indicate that adsorbed metal atoms can change the properties of the In2Se3 material itself. And interestingly, in the M-In2Se3 system, the ultraviolet (UV) region exhibits significantly enhanced absorption peaks, demonstrating that the addition of metal atoms can improve the In2Se3 material’s ability to absorb light. Finally, reference light absorption spectrum, it is found that placing spherical metal nanoparticles on top of 100 nm thick In2Se3 nanosheets could excite the localized surface plasmon resonance. And among them, Au nanoparticles have the most impact on the localization of electric fields. It indicates that the introduction of Au significantly enhances the absorption properties of the material. This suggests that the metal atom adsorbed In2Se3 system will be favorable for its application in optical devices as well as electronic devices.

Adsorption of metals on Si9C15 monolayer for optoelectronic applications

Two dimensional materials have a bright application prospect in the field of optoelectronic devices. As a newly discovered polymorph of the third-generation semiconductor SiC, Si9C15's single-layer structure may have excellent optoelectronic properties, which has significant practical implications for the study of two-dimensional Si9C15. By employing the first-principles density functional theory, a comprehensive analysis is performed on the electronic, magnetic, work function, and optical absorption properties of a monolayer structure Si9C15 with metal atom adsorption. The adsorption of different metal semiconductors has changed their properties. The adsorption of metal atoms not only reduces the work function of Si9C15, but also enhances its light absorption ability in the visible light region. This finding highlights the potential for enhancing the optical properties of the Si9C15 system through metal adsorption. The utilization of spherical metal nanoparticles on Si9C15 nanosheets to induce local surface plasmon resonance is an exciting development. The results indicate that the Si9C15 system adsorbed with metal atoms could be employed in the manufacturing of spin electronic device, field emission devices, and solar photovoltaic devices. This suggests that the improved optical properties of the Si9C15 system could have significant implications for advancing these technologies.

Investigation of the Impact of Mycogenic Titanium and Selenium Nanoparticles on Fusarium Wilt Infection of Tomato Plant

We applied biosynthesized titanium and selenium nanoparticles, prepared using a fungal water extract of Trichoderma harzianum (T. harzianum), to eradicate tomota wilt infection. Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy Dispersive X-Ray analysis, and Transmission electron microscopy/X-ray diffraction (TEM/XRD) techniques were used to characterize the spherical metal nanoparticles, whose diameters were 16.0 nm for selenium nanoparticles (SeNPs) and 50.0 nm for titanium nanoparticles (TiNPs). This confirmed the efficient biosynthesis of the nanoparticles. Under greenhouse conditions, the effectiveness of TiNPs and SeNPs produced by nonpathogenic fungi (T. harzianum) against the pathogen responsible for the tomato wilt disease, Fusarium oxysporum (F. oxysporum), was studied. Based on the results, the most efficient method for combating the pathogen that causes tomato wilt was used in open fields, whereas pot studies were conducted in greenhouse conditions. All tested treatments considerably lowered tomato plant wilt disease in both the greenhouse and the open field. The disease severity was reduced by 20.4% using TiNPs at high concentrations of 150 ppm and by 41.5% using SeNPs. Compared to conventional antibiotics, the antibacterial activity assessment of the biosynthesized TiNPs and SeNPs revealed a significant effect versus pathogenic bacteria and fungi, with a negligible influence on the examined human and animal microflora. The findings showed that biosynthesized TiNPs and SeNPs can be applied to suppress the plant pathogen F. oxysporum in a way that is safe for the microflora of humans and animals. This is the first instance where the nanocidal activity of biological TiNPs and SeNPs has been used against the pathogen that causes tomato wilt.

Metal atoms adsorbed Ga2O3 monolayer: As a potential application in optoelectronic devices

Density functional theory based on first principles has been used to analyze the electronic, magnetic, work function, and optical absorption characteristics of metal atoms adsorbed Ga2O3 monolayer structures. The outcomes demonstrate that the Pt–Ga2O3 and Zn–Ga2O3 systems remain nonmagnetic semiconductor characteristics, while the Ag–Ga2O3, K–Ga2O3, Li–Ga2O3 and Na–Ga2O3 systems exhibit nonmagnetic metal behaviors. Meanwhile, the Al–Ga2O3, Cr–Ga2O3, Fe–Ga2O3 and Ni–Ga2O3 systems reveal magnetic metal behaviors, and the Au–Ga2O3, Bi–Ga2O3, Ge–Ga2O3 and Sn–Ga2O3 systems show magnetic semiconductor characteristics. Whereas the Co–Ga2O3 system emerges magnetic semimetal behavior. Furthermore, the work function of Ga2O3 adsorbed by metals are reduced. Importantly, after the adsorption of metal atoms, the optical absorption of Ga2O3 systems has been improved to varying degrees in the visible and infrared regions, and many absorption peaks have appeared, indicating that the introduction of metal atoms can improve the optical absorption of the Ga2O3 systems in both visible and near-infrared regions. Moreover, spherical metal nanoparticles placed on top of Ga2O3 nanosheets can excite localized surface plasmon resonance, which will greatly enhance the absorption properties of the structure. Therefore, the above results suggest that the metal atoms adsorbed Ga2O3 systems will be useful for the fabrication of spintronics, field emission devices and solar photovoltaic devices.

Schottky effect on the wavelength threshold for the photo-detachment from charged metallic nanoparticles

Laser-stimulated electron photo-detachment (LSPD) from nanoscale dust particles is predicted to strongly depend on the particle size. A theory of the electron photo-detachment from charged spherical metallic nanoparticles is presented. This theory is relevant to laser-stimulated photo-detachment applied to measurements of charge of nanoparticles in plasmas. Our theory predicts that the charging of nanoparticles in plasma leads to the appearance of an additional electric field, causing a change in the potential barrier at the particle boundary and consequently, a change in the effective work function, due to the Schottky effect. In this case, the critical wavelength of the laser depends not only on the work function, but also on the charge of the nanoparticles and their size.

An optical absorption of the composite with the nanoparticles, which are covered by the surfactant layer

The optical properties of the nanocomposite with two-layer spherical inclusions “metallic core – surfactant layer” have been studied in the work. The question connected with an influence of the processes at the interface “metal – adsorbate” on the excitation of the surface plasmonic resonances in the nanoparticle has been studied. The fact of splitting of the surface plasmonic resonance due to the influence of the absorption bond near the surface of the metallic nanoparticles and due to the emergence of the additional energy states has been established. The relations for the effective parameters which describe the losses of coherence under the scattering at the chemical interface have been obtained. The calculations for the frequency dependencies of the diagonal components of the dielectric permittivity tensor of the two-layer nanoparticle and for the absorption coefficient of the nanocomposite have been performed. It has been shown that the frequency dependencies for the real and imaginary parts of the longitudinal component of the dielectric tensor are close to the similar dependencies for the real and imaginary parts of the dielectric function for the spherical metallic nanoparticle. At the same time the real and imaginary parts of the transverse component weakly depend on the frequency in the visible spectrum and oscillate in the infrared range. It has been established that the absorption coefficient of the composite can have one or two maximums depending on the sizes and the material of the particles-inclusions.

Optical Absorption Coefficient and Refractive-Index Change in a Coupled Quantum Dot-Metallic Nanoparticle Structure

In the present work, we investigate the problem of the optical absorption coefficient (OAC) and refractive-index change (RIC) in a semiconductor quantum dot placed in the vicinity of a spherical metallic nanoparticle. We derive the total OAC and RIC from the density-matrix equations through different approaches, one without approximations and the other keeping only linear and third-order nonlinear terms. The derived formulae are then applied in a specific hybrid nanostructure to calculate the OAC and RIC. The results obtained from the derived formulae are used to compare cases of various interparticle distance values and applied light intensities and find that, although for specific distances and intensities the formulae may give similar results, in general, they give different results. Moreover, it becomes clear that the distance between the quantum dot and the metallic nanoparticle, in combination with the polarisation of the light field, plays a significant role in the OAC and RIC of the quantum dot. Expressly, conditional on the polarisation of the applied electric field, the OAC and RIC of the quantum dot can be either enhanced or suppressed close to the metallic nanoparticle compared to their values in the absence of the metallic nanoparticle.

Surface plasmon resonance in metal nanospheres explained with LCR circuits.

The manuscript details various simple LCR circuits to explain the experimentally observed surface plasmon resonance behavior of spherical metal nanoparticles. The results of the circuit's performance simulated using standard software like "QUCS" show similarity with SPR results in the literature, thus successfully explaining the size-effect, the influence of the surrounding dielectric medium and the proximity effect of densely packed metal nanoparticles. The study also explains these material dependent observations in terms of circuital parameters. This opens an avenue to detail the exact role of the material parameters in the influence of the surrounding dielectric medium and the proximity effect.

Radiation Efficiency of the Spherical Metallic Nanoparticles, Covered with Molecular Adsorbate Layer

Radiation Efficiency of the Spherical Metallic Nanoparticles, Covered with Molecular Adsorbate Layer

In English

An influence of the adsorbed molecules layer on the optical characteristics of the spherical metallic nanoparticles has been studied in the work. In order to do this one considers the additional term which takes into account the scattering of electrons at the interface between metal and adsorbate. The analytical expressions for the frequency dependences for the parameter of coherence loss due to the scattering at the interface “metal – adsorbed layer” have been obtained. It has been found that the presence of the adsorbed molecules results in the electron scattering anisotropy, and, hence, in the anisotropy of the optic response of such systems. The result of the indicated anisotropy is the appearance of the additional maximum in the infrared part of the spectrum in the frequency dependences for the optical characteristics. An evolution of the frequency dependences for the components of the polarizability tensor and the absorption cross-section and scattering cross-section for the two-layer spherical nanoparticles of the type “metal – adsorbate” under the variation of their geometrical parameters has been analyzed. It has been shown that the weak maximum of the real, imaginary parts and the module of the transverse component of the polarizability tensor and the absorption and scattering cross-sections in the infrared part of the spectrum appears due to inducing of the local density of the states by adsorbate. The reason of the shift of the maxima of the absorption cross-section and scattering cross-section for the nanoparticles of the constant sizes with the cores of different metals has been found. It has been demonstrated the existence of the small-scale oscillations at the frequency dependences for the components of the polarizability tensor and at the absorption and scattering cross-sections, caused by an oscillating contribution of the surface electron scattering. The dependence of the location and the value of the maximum of the absorption cross-section for the particle “metal – adsorbate” with the constant geometrical parameters and content on the dielectric permittivity of the medium, in which the nanoparticle is situated, has been proved.

Synthesis and characterization of spherical FeNi3 metallic nanoparticles based on sodium dodecyl sulfate

Synthesis and characterization of spherical FeNi3 metallic nanoparticles based on sodium dodecyl sulfate