News From the Kamat Lab

Monday, April 14, 2014Posted by Jeff Christians

KamatLab Youtube Channel

KamatLab Youtube Channel

Our group has published a variety of videos and webinar presentations through the website SlideShare. Because SlideShare is no longer supporting "Slidecasts" (Power Point presentations with audio) we have begun migrating all of our webinar presentations over to Youtube. You can now follow us on Youtube and see all of our latest updates and presentations, just click the link below!

Youtube Channel

Monday, April 14, 2014Posted by Jeff Christians

How Does a SILAR CdSe Film Grow?

Read the latest paper from the Kamat Lab!

How Does a SILAR CdSe Film Grow? Tuning the Deposition Steps to Suppress Interfacial Charge Recombination in Solar Cells

How Does a SILAR CdSe Film Grow? Tuning the Deposition Steps to Suppress Interfacial Charge Recombination in Solar Cells

Abstract: Successive Ionic Layer Adsorption and Reaction (SILAR) is a popular method of depositing the metal chalcogenide semiconductor layer on the mesoscopic metal oxide films for designing quantum dot sensitized solar cell (QDSSC) or Extremely Thin Absorber (ETA) solar cells. While this deposition method exhibits higher loading of light absorbing semiconductor layer than direct adsorption of pre-synthesized colloidal quantum dots, the chemical identity of these nanostructures and evolution of interfacial structure are poorly understood. We have now analyzed step-by-step SILAR deposition of CdSe films on mesoscopic TiO2 nanoparticle films using x-ray absorption near-edge structure analysis and probed the interfacial structure of these films. The film characteristics interestingly show dependence on the order in which the Cd and Se are deposited, and the CdSe-TiO2 interface is affected only during the first few cycles of deposition. Development of SeO2 passivation layer in the SILAR-prepared films to form TiO2/SeO2/CdSe junction facilitates an increase in photocurrents and power conversion efficiencies of quantum dot solar cells when these films were integrated as photoanodes in a photoelectrochemical solar cell.

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Monday, April 14, 2014Posted by Jeff Christians

Webinar - Band Gap Tunining in CdSeS NWs

CdSeS Nanowires. Compositionally Controlled Band Gap and Exciton Dynamics

Watch this ACS LiveSlides presentation on the synthesis of CdSeS nanowires. This webinar describes the tuning of the composition of the NWs by the ratio of Se:S precursor. This allows for the modulation of the NW band gap between 2.36 eV and 1.79 eV. The presentation is based off of the paper, recently published in Journal of Physical Chemistry Letters, entitled:

CdSeS Nanowires. Compositionally Controlled Band Gap and Exciton Dynamics.

Abstract: CdS, CdSe and ternary CdSexS(1-x) are some of the most widely studied II-VI semiconductors due to their wide range of applications and promising performance in numerous systems. One-dimensional semiconductor nanowires offer the ability to conduct charges efficiently along the length of the wire which has potential charge transport benefits compared to nanoparticles. Herein, we report a simple, inexpensive synthetic procedure for high quality CdSeS nanowires where the composition can be easily modulated from pure CdSe to pure CdS by simply adjusting the Se:S precursor ratio. This allows for tuning of the absorption and emission properties of the nanowires across the visible spectrum. The CdSeS nanowires have a wurtzite crystal structure and grow along the [001] direction. As measured by femtosecond transient absorption spectroscopy, the short component of the excited state lifetime remains relatively constant at ~10 ps with increasing Se; however the contribution of this short lifetime component increased dramatically from 8.4% to 57.7% with increasing Se content. These CdSeS nanowires offer facile synthesis and widely adjustable optical properties, characteristics which give them broad potential applications in the fields of optoelectronics, and photovoltaics.

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Thursday, April 10, 2014Posted by Jeff Christians

Dr. James Radich

Congratulations to Dr. James Radic h on successful completion of his Ph. D. in Chemical and Biomolecular Engineering! James successfully defended his doctoral thesis entitled:

Reduced Graphene Oxide-Based Nanoassembiles for Energy Storage.

Congratulations on completion of your Ph. D. James!

Monday, April 7, 2014Posted by Jeff Christians

Dr. Sachidananda Krishnamurthy

Congratulations to Dr. Sachi Krishnamurthy on successful completion of his Ph. D. in Chemistry! Sachi successfully defended his doctoral thesis entitled:

Graphene-Based Assemblies: Electron Transfer Processes and Energy Conversion Applications.

Congratulations on completion of your Ph. D. Sachi!

Mondayt, April 7, 2014Posted by Jeff Christians

Editorial on Citation

Read this editorial, entitled "Cite with a Sight," from Prashant and Journal of Physical Chemistry Letters Editor-in-Chief George C. Schatz on the important area of citations in scientific research.

"Citing references in a scientific paper is becoming an increasingly important albeit challenging experience as the volume of scientific literature continues to explode. Despite the increasing average number of cited references in published papers, important and relevant papers are sometimes absent. Journal guidelines may recommend or even require the total number of citations be kept to a modest level. Consequently, authors need a balanced approach in identifying and including only the most relevant citations. In this Editorial, we discuss the importance of selecting and citing references correctly. We also discuss the impact of cited references on published research and their role in advancing the scientific discipline."

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Wednesday, March 26, 2014Posted by Jeff Christians

Hydrogen Evolution with Gold Clusters

Read the latest paper from the Kamat Lab!

Glutathione Capped Gold Nanoclusters as Photosensitizers. Visible Light Induced Hydrogen Generation in Neutral Water

Abstract: Glutathione capped metal nanoclusters (Aux-GSH NCs) which exhibit molecular like properties are employed as a photosen-sitizer for hydrogen generation in a photoelectrochemical cell (PEC) and a photocatalytic slurry reactor. The reversible re-duction (E0= -0.63 V vs. RHE) and oxidation (E0= 0.97 V and 1.51 V vs. RHE) potentials of these metal nanoclusters make them suita-ble for driving the water splitting reaction. When a mesoscopic TiO2 film sensitized by Aux-GSH NCs was used as the pho-toanode with a Pt counter electrode in aqueous buffer solution (pH = 7), we observe significant photocurrent activity under visible light (400 - 500 nm) excitation. Additionally, sensitizing Pt/TiO2 nanoparticles with Aux-GSH NCs in an aqueous slurry system and irradiating with visible light produced H2 at a rate of 0.3 mmole of hydrogen/hr/gram of Aux-GSH NCs. The rate of H2 evolution was significantly enhanced (~5 times) when a sacrificial donor, such as EDTA, was introduced into the sys-tem. Using metal nanoclusters as a photosensitizer for hydrogen generation lays the foundation for the future exploration of other metal nanoclusters with well controlled numbers of metal atoms and capping ligands.

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