Catalysis & Nanomaterials Laboratory, Rice University, Houston Dec 2009-Present
Primary Research Projects
1. Developing a novel hydrophobically modified sulfonated polymer for oil mobilization in reservoirs
A novel, scalable and inexpensive synthesis method was developed using readily available polystyrene sulfonate and selectively desulfonating it to introduce hydrophobicity into the molecule. The controlled hydrophobicity was tunable so as to impart surface activity and obtain polymeric surfactants that reduces interfacial tension by 3-4 orders of magnitude compared to the precursor with oil such as toluene (6 x 10-3 mN/m). The polymeric surfactant is stable at temperatures as high as 150 ºC and salinity as high as 20 wt% NaCl (3 M ionic strength).
2. Developing a surfactant-stabilized carbon black system for oil detection in underground reservoirs
Carbon black, readily available in bulk quantities, was stabilized into an aqueous system using surfactants such as Hitenol and Avanel. This carrier molecule, combined with a tag molecule that easily partitions into an oil phase such as triphenylamine, comprises a nanoreporter molecule. Stability tests showed these molecules can handle the most extreme of reservoir conditions and lab scale breakthrough studies using crushed Berea sandstone showed good transport properties in a packed bed column with no oil present. When the crushed sandstone was saturated with oil, the tag partitioned into the oil phase and characterizing the effluent (to simulate a production well) helped quantify the oil content in the column.
3. Construction of a chemical vapor deposition (CVD) reactor from scratch for synthesizing vertically aligned single wall carbon nanotube arrays (VANTA)
A high purity, ultralow vacuum CVD system was built in a time period of less than an year for testing out various catalyst formulations to influence length and chirality of single wall carbon nanotubes (SWCNTs), especially vertical array growth of SWCNTs. The system has a lot of control setup and characterization built into it and allows for in-situ imaging of growth, quick turnaround of samples, ability to use multiple inlet gas feeds and running at atmospheric/vacuum as desired. This work helped with understanding process and reactor design on a high level.
4. Studying the effect of metal dopants on the ability of VANTA growth catalysts to tune nanotube growth towards preferential chirality and/or length
Using iron as a growth catalyst for VANTAs, several different Group 15 and 16 elements were studied to test the effect on growth. In particular, phosphorous had a distinct effect in controlling the average length of the nanotubes whereas sulfur and selenium affected the average growth rate. By controlling the concentration of the dopant used, the growth rate could be tuned to favor more armchair/near-armchair type SWCNTs or zigzag type SWCNTs.
5. Using agarose gel column chromatography for tunable separation of as-grown VANTA to metal- and semiconductor-enriched nanotube ensembles
As-grown carbon nanotubes are a mixture of metal and semiconductor type and thus have limited applications. A fast, high efficiency separation method was developed using gel permeation column chromatography. The as-grown SWCNTs were stabilized in water using sodium dodecylsulfate (SDS) and then passed through a column filled with Sepharose (agarose gel). SDS was then used to selectively extract metal enriched nanotubes that were about 75-80% pure, followed by nonionic surfactants from the Pluronic or Tetronic family to selectively extract semiconducting-type nanotubes that were about 95% pure. Given the nature of these surfactants, it was found that simply be heating the suspension to 300 ºC, one could remove the Pluronic/Tetronic surfactants entirely allowing to high purity semiconductor SWCNTs.
Collaboration Projects
1. Synthesis and characterization of a polystyrene sulfonate-based nanoreporter molecules for oil field applications
2. Characterization of sulfated carbon black materials for oil field applications
3. Synthesis of a polystyrene sulfonate-based polymeric surfactant by controlled sulfonation of polystyrene
4. Characterization of a novel water-soluble nanodiamond system
5. Synthesis and characterization of novel graphene oxide materials
National Institute of Technology, Karnataka, India Aug 2007-May 2009
Research Projects
1. Isolation of novel bacteria having Tannase activity
Enrichment culture technique was used to isolate a bacterium vss1, from rotting coffee pulp using complex medium having tannin as the sole carbon source. Morphological and biochemical characteristics (including 16S rDNA analysis) helped identify it as Pseudomonas fulva. In shake flask studies, extracellular activity of 0.0066 U/mL and cell-bound activity of 0.32 U/g of dry biomass was recorded. This was the first report of cell-bound activity in the case of bacterial tannase.
2. High efficiency wood stoves for rural India
Several different formulations of stove design, effluent chimney and fuel top were studied across a span of several months and a report suggesting 3 new prototypes was prepared. Of the three, 1 working prototype was implement by the Gram Panchayat (village council) in a village in the Shimoga district in Karnataka, India
Indian Institute of Science, Bangalore, India
May 2008- June 2008
Research Projects
1. Design and construction of a catalysis test chamber for UV light activated titania
An in-house, self-contained box was built from scratch inside of which was flow reactor with water cooling jacket, a waterproof UV lamp holder and 3 ports (inlet, outlet and sampling) to allow for a continuous loop of the sample under study as well as collection of small volumes at fixed time intervals for characterization.
2. Synthesis, characterization and application of anatase phase titania catalyst for UV-assisted decomposition of organic dyes in aqueous phase
Nanosized TiO2 was synthesized using solution combustion of titanyl nitrate and glycine, XRD analysis of which revealed the anatase crystalline phase to be predominant. The catalyst was then tested by forming several organic dyes such as Methylene Blue, Rhodamine B in water to simulate waste water effluent from a textile industry and decomposition of the dyes by the UV-activated titania in a flow setup. The results were compared to that of a readily available titania catalyst (Degussa P-25) and a report was made with all the findings to aid in a publication.