Ramu Pasupathi Sugavaneshwar

Solar water heating and vaporization with silicon nanoparticles at mie resonances

We propose analytically and demonstrate experimentally that an ensemble of silicon nanoparticles with different sizes can effectively absorb sunlight. Due to the extinction of silicon from UV to near-infrared region, Mie resonances in silicon nanoparticles dramatically enhance the absorption of solar light. In experiment, silicon nanoparticles dispersed in water worked as excellent sunlight-heat transducers that efficiently harvest sunlight to accelerate heating and vaporization of water by nanoscale local heating. Our study opens up the potential of silicon nanoparticles in various solar-thermal applications.

Enhanced Solar Light Absorption and Photoelectrochemical Conversion Using TiN Nanoparticle-Incorporated C3N4–C Dot Sheets

In this work, a promising strategy to increase the broadband solar light absorption was developed by synthesizing a composite of metal-free carbon nitride-carbon dots (C3N4-C dots) and plasmonic titanium nitride (TiN) nanoparticles (NPs) to improve the photoelectrochemical water-splitting performance under simulated solar radiation. Hot-electron injection from plasmonic TiN NPs to C3N4 played a role in photocatalysis, whereas C dots acted as catalysts for the decomposition of H2O2 to O2. The use of C dots also eliminated the need for a sacrificial reagent and prevented catalytic poisoning. By incorporating the TiN NPs and C dots, a sixfold improvement in the catalytic performance of C3N4 was observed. The proposed approach of combining TiN NPs and C dots with C3N4 proved effective in overcoming low optical absorption and charge recombination losses and also widens the spectral window, leading to improved photocatalytic activity.

Sunlight absorbing titanium nitride nanoparticles

The surface plasmon resonances of titanium nitride nanoparticles are broad and covers majority of the solar spectrum. In terms of integrated absorption efficiency titanium nitride nanoparticles are efficient sunlight absorbers due to these resonances, even better than gold and carbon nanoparticles which have been extensively studied so far. In experiment, titanium nitride nanoparticles were dispersed in water and the evaporation and heating rates increased by factors of four and two, respectively, compared to pure water. Our study shows that titanium nitride nanoparticles are quite useful for solar thermal heat conversion applications such as heating and distilling water.

Effects of nanoscale morphology and defects in oxide: optoelectronic functions of zinc oxide nanowires

ABSTRACT Oxide nanomaterials have been attracting growing interest for both fundamental research and industrial applications ranging from gas sensors, light-emitting devices, to photocatalysts, and solar cells. The optical and electronic properties of oxide nanomaterials are strongly dependent on their surface morphologies as well as defects, such as surface areas, aspect ratios, foreign atom impurities, and oxygen vacancies. In this review, we describe some examples of our recent contributions to the nanomaterials and devices that exhibit remarkable functionalities based on one-dimensional nanostructures of ZnO and their hetero junctions as well as their variants with appropriately incorporated dopants.

Plasmon mediated cathodic photocurrent generation in sol-gel synthesized doped SrTiO3 nanofilms

Thin films of SrTiO3 (STO) and Rh-doped SrTiO3 (Rh-STO) were synthesized by sol-gel method and loaded with Ag nanoparticles. Pristine STO films exhibited anodic photocurrent while Rh-STO exhibited cathodic photocurrent. An enhancement in the overall cathodic photocurrent is observed with Ag nanoparticle loading and an additional enhancement in the visible light range is seen from the incident photon-to-current efficiency spectrum due to synergetic effect of Rh doping and Ag loading in STO.

Effect of oxygen annealing on the photoresponse of PbSe thin films fabricated by the pulsed laser deposition method

ABSTRACT In this work, we have fabricated lead selenide (PbSe) thin films by the pulsed laser deposition method on Si/SiO2 substrates and investigated the effect of oxygen annealing (sensitization) in these films. The oxygen-sensitized films show high responsivity in the visible (VIS) and the near-infrared (NIR) region at room temperature without cooling. We also demonstrate the effective surface oxidation of PbSe thin films during the oxygen annealing process without treated with commonly used halogens that leads to a better photoresponse in these PbSe films.

Lossy plasmonic resonances in nanoparticles for broadband light absorption

We show with experiments that localized surface plasmon resonances in conductive nitride nanoparticles result in broadband light absorption covering solar spectrum. The nitride nanoparticle dispersed water was warmed and generated vapor efficiently by sunlight illumination.

Enhanced photocatalytic activity of ultra-high aspect ratio ZnO nanowires due to Cu induced defects

We report the synthesis of ZnO nanowires in ambient air at 650°C by a single-step vapor transport method using two different sources Zn (ZnO nanowires-I) and Zn:Cu (ZnO nanowires-II). The Zn:Cu mixed source co-vaporize Zn with a small amount of Cu at temperatures where elemental Cu source does not vaporize. This method provides us a facile route for Cu doping into ZnO. The aspect ratio of the grown ZnO nanowires-II was found to be higher by more than five times compared ZnO nanowires-I. Photocatalytic activity was measured by using a solar simulator and its ultraviolet-filtered light. The ZnO nanowires-II shows higher catalytic activity due to increased aspect ratio and higher content of surface defects because of incorporation of Cu impurities.