Collective optical Kerr effect exhibited by an integrated configuration of silicon quantum dots and gold nanoparticles embedded in ion-implanted silica

Revealing the Origin of Cooperative Adsorption of Chains on Nanoparticle Surfaces through Coarse-Grained Simulations

This work aims to deepen our understanding of the molecular origin of the recently observed phenomenon of polymer cooperative adsorption onto faceted nanoparticle (NP) surfaces. By exploring a large parameter space for polymer/NP interactions through coarse-grained (CG) molecular dynamics (MD) simulations, it is found that consistent with experiments the presence or absence of cooperativity is related to solvent quality and relative interaction strengths between the polymer and the adsorbent. Specifically, positive cooperativity is associated with stronger polymer-polymer interaction than polymer-surface interactions and vice versa for negative cooperativity. This contrast in interaction energies manifests in positive cooperativity (i.e., increased affinity) and negative cooperativity (i.e., decreased affinity) as concentration increases. It is also found that increasing chain length strengthens cooperativity effects and that the nanoscale confinement of polymer chains to the adsorbing facet (due to weaker affinity to corners and edges) enhances positive cooperativity but weakens negative cooperativity. Moreover, adsorption onto a spherical NP shows stronger positive cooperativity but weaker negative cooperativity compared with adsorption onto a cubic NP of equal surface area. It was further found that as polymer bulk concentration increases, the free energy of adsorption decreases in positive cooperativity, increases in negative cooperativity, and is independent of concentration in noncooperative systems consistent with the phenomenological explanation of cooperativity. We further found that positive cooperativity is associated with growing fluctuations in the adsorption density at critical bulk polymer concentrations. This behavior can be attributed to the competition between enthalpic gains and entropic losses upon adsorption. Overall, our results shed light on the microscopic origin of cooperative adsorption and the role of solvent quality, which can be leveraged in, for example, controlling NP growth into target shapes and designing NP catalysts with improved performance.

Impacts of four commonly used nanoparticles on the metabolism of a marine bivalve species, Tegillarca granosa

The rapid development of nanotechnology boosts the massive production and utilization of various nanoparticles (NPs). However, the NPs escaped into environments form emergent pollutants, which pose a potential threat to marine organisms and ecosystems. Due to their sessile filter-feeding lifestyle, marine bivalves live in pollution-prone coastal areas are more susceptible to land-sourced pollutants such as NPs. However, the impacts of many NPs on the metabolism, one of the most critical physiological processes of an organism, still remain largely unknown in bivalve species. To fill up this knowledge gap, in this study the impacts of four commonly used NPs (nZnO, nFe₂O₃, nCuO, and multi-walled carbon tube (MWCNT)) on the filtration rate, oxygen consumption rate, ammonia excretion rate, and O:N ratio were investigated in the blood clam, Tegillarca granosa. In addition, the expressions of ten key metabolism-related genes upon exposure to these NPs were also analyzed. The results demonstrated that exposure of blood clams to the NPs resulted in a reduction in the food intake (indicated by declined filtration rate), a shift in the metabolism substance, and disruptions in key metabolism-related molecular pathways (i.e., glycolysis and tricarboxylic acid cycle), which may render blood clam in energy shortage and thus pose significant threat to the health of this important bivalve species.

Dynamic compressibility and third-order optical nonlinearities in carbon/metal-based nanofluids

The influence of the superposition of two high-irradiance optical beams on the mechanical properties exhibited by carbon nanotubes decorated with platinum nanoparticles was analyzed. The change in density, compressibility modulus and acoustic velocity in the samples suspended in acetone and ethanol was estimated by measuring the nonlinear refractive index tested by a two-wave mixing experiment. The nanotubes were prepared by a spray pyrolysis processing route and the metal decoration was carried by chemical vapor deposition. High-Resolution Transmission Electron Microscopy studies confirmed the multiwall nature of the carbon nanotubes; while energy-dispersive X-ray spectroscopy reveals the separated presence of platinum nanoparticles incorporated to the hybrid nanostructures. An Nd-YAG laser system emitting at 532 nm wavelength with 4 ns pulse duration was used for conducting the third-order nonlinear optical evaluations by a standard optical Kerr gate technique. Comparative experiments showed that the composition of the liquid solution plays an important role in the manipulation of the density exhibited by the nanofluids. Remarkably, the incorporation of Pt in the tubes originates stronger changes of the mechanical characteristics induced by optical nonlinearities in the nanofluids irradiated by nanosecond pulses. Within this work, it is highlighted that potential applications for developing multivalent logic operations by fuzzy mechano-optic effects exhibited by nanofluids can be contemplated.

Chaotic Signatures Exhibited by Plasmonic Effects in Au Nanoparticles with Cells

The evolution of the optical absorptive effects exhibited by plasmonic nanoparticles was systematically analyzed by electronic signals modulated by a Rössler attractor system. A sol-gel approach was employed for the preparation of the studied Au nanoparticles embedded in a TiO₂ thin solid film. The inclusion of the nanoparticles in an inhomogeneous biological sample integrated by human cells deposited in an ITO glass substrate was evaluated with a high level of sensitivity using an opto-electronic chaotic circuit. The optical response of the nanoparticles was determined using nanosecond laser pulses in order to guarantee the sensing performance of the system. It was shown that high-intensity irradiances at a wavelength of 532 nm could promote a change in the absorption band of the localized surface plasmon resonance associated with an increase in the nanoparticle density of the film. Moreover, it was revealed that interferometrically-controlled energy transfer mechanisms can be useful for thermo-plasmonic functions and sharp selective optical damage induced by the vectorial nature of light. Immediate applications of two-wave mixing techniques, together with chaotic effects, can be contemplated in the development of nanostructured sensors and laser-induced controlled explosions, with potential applications for biomedical photo-thermal processes.

Surface plasmon resonance in gold nanoparticles: a review

In the last two decades, plasmon resonance in gold nanoparticles (Au NPs) has been the subject of intense research efforts. Plasmon physics is intriguing and its precise modelling proved to be challenging. In fact, plasmons are highly responsive to a multitude of factors, either intrinsic to the Au NPs or from the environment, and recently the need emerged for the correction of standard electromagnetic approaches with quantum effects. Applications related to plasmon absorption and scattering in Au NPs are impressively numerous, ranging from sensing to photothermal effects to cell imaging. Also, plasmon-enhanced phenomena are highly interesting for multiple purposes, including, for instance, Raman spectroscopy of nearby analytes, catalysis, or sunlight energy conversion. In addition, plasmon excitation is involved in a series of advanced physical processes such as non-linear optics, optical trapping, magneto-plasmonics, and optical activity. Here, we provide the general overview of the field and the background for appropriate modelling of the physical phenomena. Then, we report on the current state of the art and most recent applications of plasmon resonance in Au NPs.

Nonlinear optical properties of metal nanoparticles: a review

Metal nanoparticles (MNPs) hold great technological promise because of the possibility of engineering their electronic and optical properties through material design.