Optical limiting applications of resonating plasmonic Au nanoparticles in a dielectric glass medium.

Plasmonic nanostructures exhibiting high optical nonlinearities are widely used in the rapidly growing modern nanotechnology of nonlinear optics including biomedical applications due to their tunable plasmonic behavior. In this work, we investigate the nonlinear optical properties of uniformly distributed Au nanoparticles (NPs) embedded in pre-synthesized sodium-zinc borate glass by the well-known ion-exchange technique for optical limiting (OL) applications. Various techniques such as optical absorption spectroscopy, x-ray photoelectron spectroscopy, Transmission Electron Microscope (TEM), Photoluminescence, Time of Flight secondary mass spectroscopy and the Z scan technique were used for the characterization of these NPs. TEM confirmed spherically shaped Au NPs with varying sizes of up to 16 nm, in agreement with optical absorption spectroscopy. Nonlinear optical (NLO) properties of these Au NPs were investigated by using an open as well as close aperture Z scan technique which exhibited enhanced optical nonlinearities. The two-photon absorption (2PA) coefficients demonstrated an increasing trend while the OL threshold values demonstrated a decreasing trend as a function of heat treatment. The improved 2PA coefficients and decreased OL threshold values endorsed the Au NPs containing glasses as contending materials for the fabrication of promising optical limiters for the protection of eyes and other sensitive instruments from laser induced damages.

Thermally induced structural metamorphosis of ZnO:Rb nanostructures for antibacterial impacts.

In this work, we report on the synthesis of pure and Rb doped ZnO (ZnO:Rb) nanoparticles by a simple combustion technique followed by thermal treatment in an open-air atmosphere. The prepared samples were characterized using UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), photoluminescence, Raman spectroscopy and scanning electron microscopy. The wurtzite hexagonal phase structure of ZnO and a secondary phase of Rb2ZnO2 was observed after doping ZnO with Rb. FTIR and DSC confirmed the functional groups and the thermal stability of the ZnO samples. Field emission scanning electron microscope showed an irregular shaped agglomerated morphology for the ZnO:Rb samples. The chemical states of the undoped and Rb doped samples were identified using X-ray photoelectron spectroscopy for both pure and ZnO:Rb samples. In addition, ZnO:Rb samples exhibit good antimicrobial activities against Bacillus subtilis with a change in antibacterial behaviour as compared to pure ZnO structures indicating their multifunctional applications.

Navigable Channel-Based Trans-Sulcal Resection of Third Ventricular Colloid Cysts: A Multicenter Retrospective Case Series and Review of the Literature.

BACKGROUND: Developments in frameless neuronavigation and tubular retractors hold the potential for minimizing iatrogenic injury to the overlying cortex and subcortical tracts, with improved access to the ventricular system. The objective of the present study was to evaluate the surgical outcomes after resection of third ventricular colloid cysts using an integrated neuronavigation and channel-based approach. METHODS: We performed a multicenter retrospective analysis of surgical Outcomes after surgical resection of third ventricular colloid cysts via a transtubular trans-sulcal approach. RESULTS: A total of 16 patients were included, with a mean age of 42 years (range, 23-62 years). The mean maximum diameter of cysts was 14 mm (range, 7-28 mm), and preoperative hydrocephalous was present in 12 patients (75%). Gross total resection was achieved in all 16 cases. Of the 12 patients, 4 (25%) had undergone septum pellucidotomy, in addition to cyst resection. No case had required conversion to open craniotomy. No perioperative mortalities occurred. Three patients (18.8%) had developed transient memory deficits, 1 of whom had also developed a pulmonary thromboembolism. The median length of hospital stay was 4 days (range, 2-18 days). All the patients reported resolution of preoperative symptoms at the 1-month follow-up examination. Only 1 patient (6.25%) had required insertion of a ventriculoperitoneal shunt. The median follow-up duration was 6.5 months (range, 3-24 months), and no recurrences were observed. CONCLUSION: Use of a channel-based navigable retractor provided a minimal trans-sulcal approach to third ventricular colloid cysts with the benefit of bimanual surgical control in an air medium for definitive resection of third ventricular colloid cysts.

Transition-Metal-Free Regiospecific Aroylation of Nitroarenes Using Ethyl Arylacetates at Room Temperature.

A novel regiospecific C(sp3)-C(sp2) coupling between ethyl arylacetates and nitroarenes has been developed to deliver biaryl ketones in excellent yields. The protocol is metal-free, mild, and compatible with a number of functional groups on both of the reacting partners.

Synthesis, characterization and multifunctional properties of plasmonic Ag-TiO2 nanocomposites.

We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.

Plasmonic resonance of Ag nanoclusters diffused in soda-lime glasses.

Silver nanoclusters were prepared in a soda-lime glass matrix through the ion-exchange (Ag(+)↔ Na(+)) method followed by thermal annealing in an air atmosphere. The nanoscale patterning of Ag nanoclusters embedded in a soda lime glass matrix in an air atmosphere at different annealing temperatures has been investigated. During annealing, Ag(+) is reduced to Ag(0) and subsequently forms silver nanoparticles inside the glass matrix. A blue shift of 20 nm has been observed as a function of the post annealing temperature. The photoluminescence intensity is highest for an annealing temperature of 500 °C for 1 h and continuously decreases as annealing temperature increases up to 600 °C. The presence of spherical nanoparticles with a maximum particle size of 7.2 nm has been observed after annealing at 600 °C for 1 hour, which is consistent with Mie theory based results.

Polymorphic transformations and optical properties of graphene-based Ag-doped titania nanostructures.

TiO2 is the most studied semiconductor material for photovoltaics and photocatalyst applications, but due to a very large electron hole recombination process it is difficult to use it as a photovoltaics material. In this context graphene-decorated Ag-doped TiO2 nanostructures have been synthesized by a simple, cost effective chemical method. In this paper, we have studied the structural transformations and electronic band structure of Ag-doped TiO2 due to the incorporation of graphene oxide. Pure rutile and anatase-rutile mixed phases of TiO2 nanoparticles were obtained by Ag doping and annealing at 400 °C. A large red shift was observed in most of the graphene-decorated, doped TiO2 hybrid nanostructures, which is because of the electron transfer between the conduction bands of the doped TiO2 and the multilayer graphene. The Ag-doped TiO2 nanoparticles appear in the shape of a bunch of bananas (or rice-like) because of the jumbled collection of particles, which remain unaltered even after graphene decoration. The strong electrical coupling of Ag-doped TiO2 with reduced graphene oxide produces an advanced hybrid material useful for superior photovoltaics, photocatalytic activity and other applications.

Design and synthesis of 1,3-biarylsulfanyl derivatives as new anti-breast cancer agents.

A new series of 1,3-biarylsulfanyl derivatives (homodibenzyl core motif) have been designed and synthesized as new estrogen receptor ligands by chopping benzothiophene core of raloxifene to engender seco-raloxifene scaffold. All the synthesized compounds were screened for anti-proliferative, anti-osteoporotic, and anti-implantation activity. Compounds (35, 36) having basic amino anti-estrogenic side chain were exhibiting potential anti-proliferative activity in MCF-7, MDA-MB-231 and ishikawa cell lines. Some of the synthesized compounds having homodibenzyl motif (5, 8, 10) have shown moderate anti-osteoporotic activity.

NADH-oxidase, NADPH-oxidase and myeloperoxidase activity of visceral leishmaniasis patients.

It is believed that the enhanced capability of activated macrophages to resist infection is related to the remarkable increase in the production of oxygen metabolites in response to phagocytosis. Both the production of H2O2 and the oxidation of NAD(P)H are directly dependent upon NAD(P)H-oxidase. It has been established that the respiratory burst is due to activation of NAD(P)H-oxidase localised in the plasmalemma. Myeloperoxidase is believed to be involved in augmenting the cytotoxic activity of H2O2. Low NADH-oxidase, NADPH-oxidase and myeloperoxidase activity were observed in monocytes of patients with active visceral leishmaniasis as compared with healthy controls. These results suggest that low NADH-oxidase, NADPH-oxidase and myeloperoxidase activities may account for persistence of Leishmania parasites in visceral leishmaniasis.

Immunoblot analysis of the humoral immune response to Leishmania donovani polypeptides in cases of human visceral leishmaniasis: its usefulness in prognosis.

Sera from Indian patients with parasitologically confirmed visceral leishmaniasis were studied by immunoblot analysis in order to identify a specific pattern for Leishmania infection. A soluble extract of Leishmania donovani was used as antigen. At diagnosis the sera from patients with visceral leishmaniasis specifically recognized fractions represented by bands of 201 kDa (50% of serum samples), 193 kDa (60%), 147 kDa (50%), 120 kDa (60%), 100 kDa (50%), 80 kDa (80%), 70 kDa (70%), 65 kDa (100%), 50 kDa (50%), 36 kDa (50%), 20 kDa (70%), and 18 kDa (50%). The 65-kDa band, common to all patients infected with Leishmania parasites, was found at the time of diagnosis. However, the immunoblot pattern changed after patients were treated and cured with sodium antimony gluconate (SAG; n =10) or miltefosine (n =10), as was evident from blots of sera obtained pretreatment and at 1, 3, and 6 months posttreatment. At 6 months posttreatment, immunoblots of sera from patients on the SAG regimen showed the disappearance of all bands except the 70-kDa band. Similarly, sera from those on the miltefosine regimen showed the disappearance of all bands except the 65- and 70-kDa bands. This study shows that Western blot analysis is a sensitive test for detection of anti-Leishmania antibodies. Moreover, the persistence of reactivity with the 65- and 70-kDa bands in the sera of all groups shows its promise as a diagnostic and prognostic tool.