Dhiman Bhattacharyya

Geometrical modifications and tuning of optical and surface plasmon resonance behaviour of Au and Ag coated TiO2 nanotubular arrays

A protocol for surface structuring and shape modifications of anodized TiO2 nanotubes by controlling the electric field is presented. The shape and size control of nanotubes is essential in order to achieve more control over optical and electronic properties of nanotubes such as effective band gap, light absorption capabilities, photoelectrochemical response, Raman properties, as well as appearance of the localized states. A surface plasmon resonance (SPR) study was performed using these newly developed nanotubes. It was observed that noble metal treated nanotube assemblies exhibit a ‘slow photon effect’ and plasmon-exciton interaction. Such a ‘slow photon’ effect is highly advantageous to improve photoelectrochemical (PEC) performance and quantum efficiency if plasmonic PEC activity is coupled with it in the SPR region. The FDTD simulations of tilted nanotubes suggest that the maximum surface field confinement can be realized for a lower bend angle of 8° and this confinement diminishes when inclination of the nanotubes increases further.

Electrochemical detection of methyl nicotinate biomarker using functionalized anodized titania nanotube arrays

Sensing and detection of volatile organic compounds (VOCs) from exhaled breath is a possible method for early diagnosis of several pulmonary diseases. The use of solid-state TiO2 nanotube array sensors for VOC sensing applications has been of great interest. In this study, titania nanotubular arrays (TNAs) were synthesized through electrochemical anodization and used for the electrochemical detection of methyl nicotinate biomarker vapor. Functionalization of the TNA with cobalt was found to be necessary for methyl nicotinate detection. Titanium dioxide films synthesized through high temperature oxidation and functionalized with cobalt were also compared with cobalt functionalized TNA. The ordered TNA demonstrated itself to be an effective substrate for cobalt deposition and subsequent biomarker detection over thin titanium dioxide films. Surface analysis of the cobalt functionalized TNA by x-ray photoelectron spectroscopy (XPS) studies observed cobalt deposits exist as cobalt hydroxide on the surface. Exposure of the sensor surface to methyl nicotinate vapor results in the reduction of cobalt hydroxide to cobalt metal on the surface. Two mechanisms have been proposed to describe the binding of the nicotinate biomarker to cobalt functionalized TNA consistent with the XPS studies and band theory.

Detection of Four Distinct Volatile Indicators of Colorectal Cancer using Functionalized Titania Nanotubular Arrays

Screening of colorectal cancer is crucial for early stage diagnosis and treatment. Detection of volatile organic compounds (VOCs) of the metabolome present in exhaled breath is a promising approach to screen colorectal cancer (CRC). Various forms of volatile organic compounds (VOCs) that show the definitive signature for the different diseases including cancers are present in exhale breathe. Among all the reported CRC VOCs, cyclohexane, methylcyclohexane, 1,3-dimethyl- benzene and decanal are identified as the prominent ones that can be used as the signature for CRC screening. In the present investigation, detection of the four prominent VOCs related to CRC is explored using functionalized titania nanotubular arrays (TNAs)-based sensor. These signature biomarkers are shown to be detected using nickel-functionalized TNA as an electrochemical sensor. The sensing mechanism is based on the electrochemical interaction of nickel-functionalized nanotubes with signature biomarkers. A detailed mechanism of the sensor response is also presented.

Significance of graphitic surfaces in aurodicyanide adsorption by activated carbon: Experimental and computational approach

Despite tremendous developments in industrial use of activated carbon (AC) for gold adsorption, specific aurodicyanide [Au(CN)2-] adsorption sites on the carbon have intrigued researchers. The graphitic structure of AC has been well established. Previously radiochemical and now, XPS and Raman characterizations have demonstrated higher site-specific gold adsorption on graphitic edges. Morphological characterizations have revealed the presence of slit-pores (5–10 A). Molecular-dynamics-simulation (MDS) performed on graphitic slit-pores illustrated gold-cyanide ion-pair preferentially adsorbs on edges. Ab-initio simulations predicted lower barrier for electron sharing in pores with aurodic yanide, indicating tighter bonding than graphitic surface and was well supported by Gibbs energy calculations too. Interaction energy as function of the separation distance indicated tighter bonding of gold cyanide to the graphite edges than water molecules. Selective adsorption of aurodicyanide ion-pair seems to be related to low polarity of gold complex and its accommodation at graphitic edges.

Behavior of tire derived pre-functionalized carbon black for uranium adsorption

Extracting uranium from the solution phase has been a challenge as very few sorbents present high adsorption efficiency. A novel adsorbent in the form of Recycled Tire Carbon Black (RTCB), derived from pyrolysis of used tires, has shown promising results in adsorbing uranium from solution phase better than other functionalized carbon materials. The RTCB has been presented as a cheap and effective sorbent whose properties don’t need to be altered to obtain nearly 97% adsorption and 99% elution using 0.15M HCl. Kinetic tests were performed to understand the adsorption rates. Langmuir isotherm model estimated that the adsorption capacity was ∼45.45 mg U/g RTCB at 80 °C with enhanced adsorption kinetics predicted by first order rate laws. In addition, the RTCB demonstrated better adsorption performance at lower pH. Characterization preformed using BET, illustrated that the surface area of the RTCB was 57 m2/g while FTIR confirmed the presence of thiol (R-S-H) functional group on the surface.