Throughout the history of science, comparison among calculated parameters and experimental observables has been considered as obvious to accomplish and reciprocate a fundamental hypothesis. The exploitation of sharp edges toward a plethora of paraphernalia has been continued from the prehistoric evidence to modern nanotechnology. To validate the hypotheses of the sharp edges, gold nanostars that exhibit their localized surface plasmon resonances in the visible−near-infrared region and contain multiple sharp tips have been considered as the model structures. Efficient control on the length and sharpness of the spikes has been achieved by judicious manipulation of the respective synthetic protocol. The electromagnetic simulation considering the topological parameters demonstrates an exotic interplay between the depolarization factor (P z ) and aspect ratio (α) to express the strength of the electric field generated at the tip heads as a function of their sharpness. Subsequent profiling of photothermal response caused by resistive heat exhibits an outstanding proof-of-concept resemblance between the local thermal manipulation and replicated in vitro laboratory experiment. Thus, the present work investigates an interdisciplinary analytical landscape enumerating the role of sharpness on the enhanced field and the temperature distribution localized at the tip head in the realm of plasmonic photothermal therapy.

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The use of nanotechnology in nanoparticle-based cancer therapeutics is gaining impetus due to the unique biophysical properties of nanoparticles at the quantum level. Silver nanoparticles (AgNPs) have been reported as one type of potent therapeutic nanoparticles. The present study is aimed to determine the effect of AgNPs in arresting the growth of a murine fibrosarcoma by a reductive mechanism. Initially, a bioavailability study showed that mouse serum albumin (MSA)-coated AgNPs have enhanced uptake; therefore, toxicity studies of AgNP-MSA at 10 different doses (1-10 mg/kg b.w.) were performed in LACA mice by measuring the complete blood count, lipid profile and histological parameters. The complete blood count, lipid profile and histological parameter results showed that the doses from 2 to 8 mg (IC 50 : 6.15 mg/kg b.w.) sequentially increased the count of leukocytes, lymphocytes and granulocytes, whereas the 9-and 10-mg doses showed conclusive toxicity. In an antitumor study, the incidence and size of fibrosarcoma were reduced or delayed when murine fibrosarcoma groups were treated by AgNP-MSA. Transmission electron micrographs showed that considerable uptake of AgNP-MSA by the sentinel immune cells associated with tumor tissue and a morphologically buckled structure of the immune cells containing AgNP-MSA. Because the toxicity studies revealed a relationship between AgNPs and immune function, the protumorigenic cytokines TNF-a, IL-6 and IL-1b were also assayed in AgNP-MSA-treated and non-treated fibrosarcoma groups, and these cytokines were found to be downregulated after treatment with AgNP-MSA. Cellular & Molecular Immunology

Hybrid semiconductor−plasmonic metal nanostructures (NSs) tailoring of zinc oxide−gold (ZnO−Au) have been synthesized by direct addition of an aliquot of ZnO quantum dots (QDs) to aqueous dispersions of gold nanoparticles (NPs) of five different sizes. Gold nanoparticles of variable sizes have been prepared by Frens' citrate reduction procedure and ZnO QDs by alkaline hydrolysis of zinc acetate dihydrate in methanol. The optical properties of hybrid ZnO− Au nanostructures have been explored by absorption, photoluminescence, and Raman spectroscopy; the intrinsic changes in the optical characteristics of the individual components reflect strong interfacial interaction between ZnO and Au nanostructures. The binding of ZnO QDs to the colloidal gold particles has further been elucidated by Fourier transform infrared spectroscopy and cyclic voltammetry measurements. The morphology and crystallinity of the ZnO−Au NSs have been characterized by transmission electron microscopy, high resolution transmission electron microscopy, selected area electron diffraction, and X-ray diffraction techniques. Absorption spectral studies have revealed that ZnO QDs attached on the size-specific Au NPs elicites the modification of band gap in hybrid semiconductor−metal nanostructures. The catalytic activities of the as-prepared ZnO−Au NSs consisting of gold nanoparticles of variable sizes have been probed by employing photochemical decomposition of Evans blue under visible light irradiation as the model reaction. Finally, the trends in the alteration of different interaction parameters in structuring hybrid semiconductor−metal nanostructures with the band gap have been correlated.

Physicochemical aspects of anisotropic gold nanostructures have been of considerable interest due to intrinsic shape-dependent phenomena that open up newer perspectives from nanoscale electromagnetism to basic thermodynamics since gold has a highly symmetric facecentered cubic (fcc) structure and usually tends to afford a spherical geometry to reduce surface free energy. The emergence of novel properties of these anisotropic structures could be attributed to the lack of symmetry at the interface or to the confinement of electrons that does not scale linearly with size. Based on these concepts, anisotropic gold nanospike has been chosen as a typical nanostructural system that possesses different surface energy around the nanostructure in comparison to isotropic gold nanosphere to quantify the precise surface energy at the tips of these intricate nanostructures. Cetyltrimethylammonium bromide-stabilized gold nanospheres and nanospikes have been synthesized in aqueous medium under ambient conditions. Since fluorescence spectroscopy is a very sensitive technique, fluorescent dye, alizarin red, has been employed as a local probe to elucidate the detailed spectral characteristics of the metal−probe hybrid assemblies. The influence of morphological anisotropy of these nanostructures has been, further, emphasized by following the temporal changes in the emission characteristics during the photoinduced conversion of gold nanospikes to nanospheres under NIR laser irradiation. Experimental realization of excess surface energy at the tips of the nanospikes has been calculated from theoretical perspectives.