Department of Chemical Engineering

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Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

A plasma-enhanced atomic layer deposition (ALD) process using the Ag(fod)(PEt3) precursor [(triethylphosphine)(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)silver(I)] in combination with NH3-plasma is reported. The steady growth rate of the reported process (0.24 ± 0.03 nm/cycle) was found to be 6 times larger than that of the previously reported Ag ALD process based on the same precursor in combination with H2-plasma (0.04 ± 0.02 nm/cycle). The ALD characteristics of the H2-plasma and NH3-plasma processes were verified. The deposited Ag films were polycrystalline face-centered cubic Ag for both processes. The film morphology was investigated by ex situ scanning electron microscopy and grazing-incidence small-angle X-ray scattering, and it was found that films grown with the NH3-plasma process exhibit a much higher particle areal density and smaller particle sizes on oxide substrates compared to those deposited using the H2-plasma process. This control over morphology of the deposited Ag is important for applications in catalysis and plasmonics. While films grown with the H2-plasma process had oxygen impurities (â9 atom %) in the bulk, the main impurity for the NH3-plasma process was nitrogen (â7 atom %). In situ Fourier transform infrared spectroscopy experiments suggest that these nitrogen impurities are derived from NHx surface groups generated during the NH3-plasma, which interact with the precursor molecules during the precursor pulse. We propose that the reaction of these surface groups with the precursor leads to additional deposition of Ag atoms during the precursor pulse compared to the H2-plasma process, which explains the enhanced growth rate of the NH3-plasma process. © 2017 American Chemical Society.

World University root node

Chemistry of Materials

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt3) and NH3-Plasma

Silver nanoparticles are widely used in the field of plasmonics because of their unique optical properties. The wavelength-dependent surface plasmon resonance gives rise to a strongly enhanced electromagnetic field, especially at so-called hot spots located in the nanogap in-between metal nanoparticle assemblies. Therefore, the interparticle distance is a decisive factor in plasmonic applications, such as surface-enhanced Raman spectroscopy (SERS). In this study, the aim is to engineer this interparticle distance for silver nanospheres using a convenient wet-chemical approach and to predict and quantify the corresponding enhancement factor using both theoretical and experimental tools. This was done by building a tunable ultrathin polymer shell around the nanoparticles using the layer-by-layer method, in which the polymer shell acts as the separating interparticle spacer layer. Comparison of different theoretical approaches and corroborating the results with SERS analytical experiments using silver and silver-polymer core-shell nanoparticle clusters as SERS substrates was also done. Herewith, an approach is provided to estimate the extent of plasmonic near-field enhancement both theoretically as well as experimentally. © 2017 American Chemical Society.

Fulltext

ACS Applied Materials and Interfaces

Plasmonic Near-Field Localization of Silver Core-Shell Nanoparticle Assemblies via Wet Chemistry Nanogap Engineering

The stability analysis is presented for a thin viscous liquid film flowing inside a uniformly heated horizontal cylinder that is rotating about its axis. The free surface evolution equation for the liquid-gas interface is obtained by simplifying the Navier-Stokes and energy equations within the lubrication approximation.Various dimensionless numbers are obtained that quantify the effect of gravity, viscous drag, inertia, surface tension, and thermocapillary stress. The film thickness evolution equation is solved numerically to obtain two-dimensional, steady state solutions neglecting axial variations. A liquid pool forms at the bottom of the cylinder when gravity dominates other forces. This liquid pool is shifted in the direction of rotation when inertia or viscous drag is increased. Small axial perturbations are then imposed to the steady solutions to study their stability behavior. It is found that the inertia and capillary pressure destabilize whereas the gravity and thermocapillary stress stabilize the rimming flow. The influence of Marangoni number is reported by computing the stable and unstable parametric regions. Thicker films are shown to be more susceptible to become unstable. Published by AIP Publishing.

Physics of Fluids

Stability analysis of the rimming flow inside a uniformly heated rotating horizontal cylinder

This research work numerically analyzes 2D, steady state, mixed convective heat transfer for Newtonian fluids in lid driven square enclosure with centered triangular block (blockage — 10% or 30%) maintained either at the constant wall temperature or constant heat flux thermal conditions. The fluid flow in the enclosure is initiated by top moving wall in + x-direction, while all other walls are stationary. The top and bottom walls are thermally insulated. In particular, the governing field equations are solved for range of governing parameters such as, Reynolds number (1–1000), Prandtl number (1–100), and Grashof number (0–105). It is observed that the increase in inertial force enhances the heat transfer rate up to certain Reynolds number range (80–200), later deterioration of heat transfer rate is observed. Such behavior is found to be true for lower blockage (10%). Finally, functional dependence of average Nusselt number values with flow governing dimensionless parameters is developed and presented for its possible utilization in engineering and design purpose. © 2017 Elsevier B.V.

Chinese Journal of Chemical Engineering

Mixed convection characteristics in lid-driven cavity containing heated triangular block

In this work, 2D, steady, natural convection in a partially active/heated open ended square cavity subjugated to the magnetic field for incompressible, Newtonian fluid is studied and presented. A simplified double distribution function (DDF)-thermal lattice Boltzmann method (TLBM) based on single relaxation time (SRT) is utilized for solving field controlling equations. One of the vertical walls of open cavity is exposed to the heat source (i.e., heater) partially; while another vertical wall is open to ambient. In particular, the influence of various geometric as well as parametric conditions, such as heater size (LH = 0.25, 0.5, 0.75), angle of magnetic field (θM = 0° 45° and 90°), Hartmann number (0 ≤ Ha ≤ 100) and Rayleigh number (103 ≤ Ra ≤ 105) on local and global convection features have been investigated. The dependence of average Nusselt number with magneto-convective parameter (λ = Ha2/Ra) has also been illustrated. It is observed that cavity with the applied magnetic field at θM = 45° offers highest heat transfer restriction than other considered cases. Effect of heater size remains effective only at higher Ra (≥105). © 2017 Institution of Chemical Engineers

Chemical Engineering Research and Design

Effect of angle of applied magnetic field on natural convection in an open ended cavity with partially active walls

Faraday Discussions

Applications to soft matter: General discussion

Modeling and Theory: General discussion

Human embryonic stem cells (hESCs) have been used to derive trophoblasts through differentiation in vitro. Intriguingly, mouse ESCs are prevented from differentiation to trophoblasts by certain epigenetic factor proteins such as Dnmt1, thus necessitating the study of epigenetic factor proteins during hESC differentiation to trophoblasts. We used stable isotope labeling by amino acids in cell culture and quantitative proteomics to study changes in the nuclear proteome during hESC differentiation to trophoblasts and identified changes in the expression of 30 epigenetic factor proteins. Importantly, the DNA methyltransferases DNMT1, DNMT3A, and DNMT3B were downregulated. Additionally, we hypothesized that nuclear proteomics of hESC-derived trophoblasts may be used for screening epigenetic factor proteins expressed by primary trophoblasts in human placental tissue. Accordingly, we conducted immunohistochemistry analysis of six epigenetic factor proteins identified from hESC-derived trophoblasts-DNMT1, DNMT3B, BAF155, BAF60A, BAF57, and ING5-in 6-9 week human placentas. Indeed, expression of these proteins was largely, though not fully, consistent with that observed in 6-9 week placental trophoblasts. Our results support the use of hESC-derived trophoblasts as a model for placental trophoblasts, which will enable further investigation of epigenetic factors involved in human trophoblast development. © 2016 American Chemical Society.

Journal of Proteome Research

Identification of epigenetic factor proteins expressed in human embryonic stem cell-derived trophoblasts and in human placental trophoblasts

Molecular dynamics simulations of poly(acrylic acid) PAA chain in water-ethanol mixture were performed for un-ionized and ionized cases at different degree-of-ionization 0%, 80% and 100% of PAA chain by Na+ counter-ions and co-solvent (ethanol) concentration in the range 0-90 vol% ethanol. Aspects of structure and dynamics were investigated via atom pair correlation functions, number and relaxation of hydrogen bonds, nearest-neighbor coordination numbers, and dihedral angle distribution function for back-bone and side-groups of the chain. With increase in ethanol concentration, chain swelling is observed for un-ionized chain (f = 0) and on the contrary chain shrinkage is observed for partially and fully ionized cases (i.e., f = 0.8 and 1). For un-ionized PAA, with increase in ethanol fraction Pdbleth the number of PAA-ethanol hydrogen bonds increases while PAA-water decreases. Increase in Pdbleth leads to PAA chain expansion for un-ionized case and chain shrinkage for ionized case, in agreement with experimental observations on this system. For ionized-PAA case, chain shrinkage is found to be influenced by intermolecular hydrogen bonding with water as well as ethanol. The localization of ethanol molecules near the un-ionized PAA backbone at higher levels of ethanol is facilitated by a displacement of water molecules indicating presence of specific ethanol hydration shell, as confirmed by results of the RDF curves and coordination number calculations. This behavior, controlled by hydrogen bonding provides a significant contribution to such a conformational transition behavior of the polyelectrolyte chain. The interactions between counter-ions and charges on the PAA chain also influence chain collapse. The underlying origins of polyelectrolyte chain collapse in water-alcohol mixtures are brought out for the first time via explicit MD simulations by this study. © 2016 Elsevier Inc. All rights reserved.

Journal of Molecular Graphics and Modelling

Polyelectrolyte conformational transition in aqueous solvent mixture influenced by hydrophobic interactions and hydrogen bonding effects: PAA-water-ethanol

The annual water demand was about 800 BCM in 2010 and estimated to cross 1200 BCM mark in near future which is more than the utilisable water resources. The emerging water scenario is alarming, writes Prof (Dr) P.K. Tewari.