@article { ISI:000318362400053, title = {Charge storage and electron transport properties of gold nanoparticles decorating a urethane-methacrylate comb polymer network}, journal = {Nanoscale}, volume = {5}, number = {10}, year = {2013}, month = {MAR}, pages = {4404-4411}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

We propose enhanced charge storage capacity of nanoparticles based polymer films. A flat band voltage window varying from 5-7 V is obtained leading to a trapped charge density of the order of 10(13) cm(-2). These results vary for two distinct morphologies obtained due to decoration of a urethane-methacrylate comb polymer (UMCP) network by gold nanoparticles (AuNPs). Films have been further investigated for morphology, optical, charge storage, and electron transport properties using techniques like scanning electron microscopy (SEM), atomic force microscopy (AFM), absorption spectroscopy (UV-Vis), scanning tunneling microscopy/spectroscopy (STM/STS) and capacitance versus voltage (C-V) measurements. SEM and AFM confirm either the deposition of AuNPs inside the UMCP network or the formation of ring like structures depending on the deposition sequence. STS measurements performed on both films are compared with bare UMCP and AuNPs films. Current versus voltage (I-V) characteristics so obtained are discussed in the light of electron transport mechanisms in such materials.

}, issn = {2040-3364}, doi = {10.1039/c3nr00330b}, author = {Patil, Sumati and Datar, Suwarna and Rekha, N. and Asha, S. K. and Dharmadhikari, C. V.} } @article {45670, title = {Revisiting HOPG superlattices: structure and conductance properties}, journal = {Surface Science}, volume = { 658 }, year = {2017}, month = {APR}, pages = {55-60}, type = {Article}, abstract = {Superlattices observed on highly oriented pyrolytic graphite (HOPG) have been studied extensively by scanning tunnelling microscopy (STM). The interest in the study of graphite superlattices has seen a resurgence since the discovery of graphene. Single layer graphene, bilayer graphene, and few layer graphene can now be grown on different substrates. The adherence of graphene to various substrates often leads to a periodic out-of-plane modulation and superlattices due to lattice mismatch. In this paper, we report STM imaging and scanning tunnelling spectroscopy (STS) of different kinds of superlattices on HOPG characterized by a variation in lattice periodicities. Our study also shows evidence of the displacement of the topmost HOPG layer by scanning different areas of the same superlattice. A correlation between the lattice periodicity with its conductance properties is derived. The results of this work are important for understanding the origin of the superlattice structure on HOPG. Investigation of such superlattices may open up possible ways to modify two dimensional electron systems to create materials with tailored electronic properties.}, doi = {10.1016/j.susc.2016.12.002}, author = {Patil, Sumati and Kolekar, Sadhu and Deshpande, Aparna} } @article {44595, title = {Investigation of disorder in mixed phase, sp(2)-sp(3) bonded graphene-like nanocarbon}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {18}, year = {2018}, month = {APR}, pages = {2504-2512}, abstract = {

Disorder in a mixed phase, sp(2)-sp(3) bonded graphene-like nanocarbon (GNC) lattice has been extensively studied for its electronic and field emission properties. Morphological investigations are performed using scanning electron microscopy (SEM) which depicts microstructures comprising of atomically flat terraces (c-planes) with an abundance of edges (ab planes which are orthogonal to c-planes). Scanning tunneling microscopy (STM) is used to observe the atomic structure of basal planes whereas field emission microscopy (FEM) is found to be suitable for resolving nanotopography of edges. STM images revealed the hexagonal and non-hexagonal atomic arrangements in addition to a variety of defect structures. Scanning tunneling spectroscopy is carried out to study the effect of this short-range disorder on the local density of states. Current versus voltage (I-V) characteristics have been recorded at different defect sites and are compared with respect to the extent of the defect. As sharp edges of GNC are expected to be excellent field emitters, because of low work function and high electric field, enhancement in current is observed particularly when applied electric field is along basal planes. Therefore, it is worthwhile to investigate field emission from these samples. The FEM images show a cluster of bright spots at low voltages which later transformed into an array resembling ledges of ab-planes with increasing voltage. Reproducible I-V curves yield linear Fowler-Nordheim plots supporting field emission as the dominant mechanism of electron emission. Turn on field for 10 mu A current is estimated to be similar to 3 V/mu m.

}, keywords = {Field emission microscopy, Graphene-Like Nanocarbon, Scanning tunneling microscopy, Scanning Tunneling Spectroscopy}, issn = {1533-4880}, doi = {10.1166/jnn.2018.14312}, author = {Patil, Sumati and Kolekar, Sadhu and Kumar, Arvind and Alegaonkar, Prashant and Datar, Suwarna and Dharmadhikari, C. V.} } @article {44548, title = {Phenazine-containing poly(phenylenevinylene): a new polymer with impressive field emission properties}, journal = {Journal of Polymer Research}, volume = {25}, year = {2018}, month = {FEB}, pages = {Article Number: 61}, abstract = {

Phenazine-containing poly(phenylenevinylene) (P(PHN-PV)) was synthesized using Wittig-Horner polycondensation of the appropriately designed monomers viz. 5,10-dioctyl-5,10-dihydrophenazine-2,7-dicarbaldehyde and tetraethyl ((2,5-bis((2-ethylhexyl) oxy)-1,4 phenylene) bis(methylene)) bis(phosphonate). The design embraces the specific motivation of incorporating the nitrogen-containing heterocycle viz. .phenazine in poly(phenylenevinylene) backbone. P(PHN-PV) exhibited reversible redox properties. In the field emission measurements performed on the film of P(F{\textquoteright}HN-PV), the turn-on field was observed to be 1.93 V/mu m for the current density of 10 mu A/cm(2). The maximum current density of similar to 4.87 mA/cm(2) was achieved at the applied field of 3.84 V/mu m. The emission current showed impressive stability for 6 h at a constant current of 1 mu A (current density of about 20 mu A/cm(2)). These results emphasize the role of phenazine heterocycle with lone pair of electrons on nitrogen in lowering the oxidation onset and in turn reduction of the turn-on voltage.

}, keywords = {field emission, Phenazine, Poly(phenylenevinylene)}, issn = {1022-9760}, doi = {10.1007/s10965-017-1428-8}, author = {Chhatre, Shraddha and Ichake, Amol and Harpale, Kashmira and Patil, Sumati and Deshpande, Aparna and More, Mahendra and Wadgaonkar, Prakash P.} }