Xiaoli Mao

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO2 nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO2 (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO2 NCs was found at ~7.5% (SnO2/TiO2, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO2 NCs offer three benefits, (1) the incorporation of SnO2 NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO2 was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO2 NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO2 NCs to the improvement of the photovoltaic performances in the DSSCs.

Hydrothermal Growth of Aligned ZnO Nanorods along the Seeds Prepared by Magnetron Sputtering and its Applications in Quantum Dots Sensitized Photovoltaic Cells

Hydrothermal Growth of Aligned ZnO Nanorods along the Seeds Prepared by Magnetron Sputtering and its Applications in Quantum Dots Sensitized Photovoltaic Cells Well-aligned ZnO nanorods were grown on a conductive substrate via a hydrothermal route. The substrates were pre-seeded with ZnO by a technique of radio frequency (RF) magnetron sputtering. The influences of sputtering power, annealing treatment, and the size of seeds on the morphologies of the final-prepared ZnO nanorods have been studied. It was found that the length and the aspect ratio of the ZnO rods can be readily tuned by control of the ZnO seeds which results from the RF sputtering experiments. ZnO seeds deposited at low sputtering power (100~125 W) share uniform size distribution with smaller average size (~30 nm). Higher sputtering power yields longer ZnO rods with a higher aspect ratio up to ~12.5. The seed layers after annealing (~500oC) produce ZnO rods with an increased average diameter and a smaller aspect ratio, and these features benefit the electron transfer when the prepared ZnO nano-arrays are used as electrode substrates in photovoltaic cells. By deposition of hydrophilic CdSe quantum dots (QDs) on the ZnO nano-rod, the maximum photo to current efficiency (0.42%) was obtained in case of ZnO nanorod with the length of ~2.75 μm and an aspect ratio of ~9.5 obtained from the seeds after annealing.

Preparation of CdSe Quantum Dot Sensitized Solar Cells Based on Improved Successive Ionic Layer Absorption and Reaction Method

Preparation of CdSe Quantum Dot Sensitized Solar Cells Based on Improved Successive Ionic Layer Absorption and Reaction Method Particles of metals or other materials in nanometre size are called as nanoparticles (NPs). Of ten endophytic fungi screened, seven endophytic fungi namely Alternaria alternata, Botryodiplodia sp., Pestalotia sp., Fusarium sp., Aspergillus sp. Aschersonia sp. and Phomopsis sp. were able to synthesize silver nanoparticles. Silver metal nanopartites were synthesised successfully by both mycelium as well as cell filtrate of Pestalotia sp., which was initially observed by spectrometric analysis. TEM pictures revealed the synthesis of angular shape of silver nanoparticles like trigonal, pentagonal, hexagonal, few of cuboids and some were of spherical in shape too. Most of nanoparticles (76%) were found below the size of 40 nm. FTIR spectra peaks showed the presence of -NH, CO, C=C and C-H containing organic metabolites which might play a role in stabilizing the nanoparticles. Silver nanoparticles solution (0.5 mM) inhibited the growth significantly than control against all pathogenic bacteria tested. Mycosynthesized AgNPs were most active against Aeromonas hydrophila @2 μg/ml IC50 followed by Staphylococcus aureus (6 μg/ml), Escherichia coli (8μg/ml), Morganella morganii (24 μg/ml), Salmonella typhi (42 μg/ml), Enterococcus faecalis (40 μg/ml) and Klebsiella pneumoniae (50 μg/ml) respectively. Silver nanoparticles had also shown antioxidant activity with DPPH free radical scavenging with inhibitory concentration (IC50) at 47 μg /ml. To combat with new emerging pathogenic bacteria that threat our society by causing dreadful diseases, we require the development of effective therapeutics. Thus, eco-friendly synthesised antimicrobial and antioxidant silver nanoparticles allow us to suitably employing their application in nanoparticles mediated drug delivery and therapy of diseases.