Gangotri Dey

Modeling Mechanism and Growth Reactions for New Nanofabrication Processes by Atomic Layer Deposition

Recent progress in the simulation of the chemistry of atomic layer deposition (ALD) is presented for technologically important materials such as alumina, silica, and copper metal. Self-limiting chemisorption of precursors onto substrates is studied using density functional theory so as to determine reaction pathways and aid process development. The main challenges for the future of ALD modeling are outlined.

Copper reduction and atomic layer deposition by oxidative decomposition of formate by hydrazine

We have used Density Functional Theory (DFT) to study the mechanism of three step atomic layer deposition (ALD) of copper via formate and hydrazine. The technique holds promise for deposition of other transition metals.

Copper(I) carbene hydride complexes acting both as reducing agent and precursor for Cu ALD: a study through density functional theory

We propose dual functional copper complexes that may act both as reducing agents and as Cu sources for prospective Cu atomic layer deposition. The example here is a CuH carbene complex, which can donate the H− anion to another Cu precursor forming neutral by-products and metallic Cu(0). We compute that such a reaction is thermodynamically possible because the Cu–H bond is weaker than that of Cu–C (from the carbene). Most other neutral ligands such as PPh3 and BEt3 show opposite order of bond strengths. We also find that substitution in the carbene by electronegative groups reduces the Cu–H bond strength. This further facilitates the donation of H− to the surface. The most promising copper carbene precursor is computed to be 1,3-diphenyl-4,5-imidazolidinedithione copper hydride (S-NHC)–CuH.

How does an amalgamated Ni cathode affect carbon nanotube growth? A density functional theory study

This is a Density Functional Theory (DFT) study on the influence of an alloying mixture of Ni–Zn catalysts on carbon nanotube, CNT, growth. The study is inspired by the one pot synthesis of carbon nanofibers during the electrolysis of Li2CO3. Unlike CVD, CNT growth initiates at the liquid/solid, rather than gas/solid interface in the above process. The electrodes are an amalgamated Zn cathode and with a pure Ni crucible as the anode, and both zinc and nickel (or other transition metals) are required for high yield production. The use of transition metals as the catalyst for CNT, CVD growth is well known. However, in this study we show how a mixture of the Zn–Ni alloy can act as the catalyst for the effective CNT growth. Ni and Zn are taken as an example of first row transition metals with a partially empty and completely filled d orbital respectively. The study shows that the π–d bonding between the nanotube and the metal results in strong bond formation at the interface of the nanotube growth. The study remains valid for other such metal alloys with partially and completely filled d orbitals.

A biodegradable hybrid inorganic nanoscaffold for advanced stem cell therapy

Stem cell transplantation, as a promising treatment for central nervous system (CNS) diseases, has been hampered by crucial issues such as a low cell survival rate, incomplete differentiation, and limited neurite outgrowth in vivo. Addressing these hurdles, scientists have designed bioscaffolds that mimic the natural tissue microenvironment to deliver physical and soluble cues. However, several significant obstacles including burst release of drugs, insufficient cellular adhesion support, and slow scaffold degradation rate remain to be overcome before the full potential of bioscaffold–based stem-cell therapies can be realized. To this end, we developed a biodegradable nanoscaffold-based method for enhanced stem cell transplantation, differentiation, and drug delivery. These findings collectively support the therapeutic potential of our biodegradable hybrid inorganic (BHI) nanoscaffolds for advanced stem cell transplantation and neural tissue engineering.The promise of stem cell therapy for treating central nervous system disease is limited by low stem cell transplantation survival rates and poorly controlled cell fate. Here, the authors develop a biodegradable nanoscaffold for spinal cord injury that enhances transplantation and differentiation of neural stem cells and delivers drugs.