Shobha Shukla | Indian Institute of Technology Bombay (original) (raw)
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Papers by Shobha Shukla
Plasmonic nanostructures can be tuned by changing their geometry such as the aspect ratio of gold... more Plasmonic nanostructures can be tuned by changing their geometry such as the aspect ratio of gold pillars. Although they are very attractive for many applications such as biosensors, imaging beyond diffraction limit etc. there is lack of an easy, cost-effective process for implementing such structures. We report a simple, facile and manufacturable method to produce gold-polymer plasmonic nanoarrays in nanoporous alumina templates. Two dimensional arrays of gold-polymer nanocomposite support discrete plasmon resonance modes at visible and infrared frequencies. Finite element full-wave analysis in three-dimensional computational domain confirms our experimental results.
Applied Physics Letters, 2011
The local atomic structure of graphene oxide has been probed using synchrotron radiations. Detail... more The local atomic structure of graphene oxide has been probed using synchrotron radiations. Detailed investigations of recently proposed simplistic model of graphene oxide using x-ray absorption near edge spectroscopy have been performed. X-ray diffraction measurements and calculations indicate loss of coherence between graphene-like layers. However, larger in-plane structural coherence is understood to be present. Selected area electron diffraction measurements indicate the presence of graphitic regions in graphene oxide which is expected to produce interesting confinement effects in graphene oxide which could be important for the development of tunable electronic and photonic devices.
Journal of Physical Chemistry C, 2010
Journal of Physical Chemistry Letters, 2010
Acs Applied Materials & Interfaces, 2010
Medical Engineering & Physics, 2008
We report on the elemental composition of healthy and infected part of human tooth using laser in... more We report on the elemental composition of healthy and infected part of human tooth using laser induced breakdown spectroscopy (LIBS). We have used prominent constituent transitions in laser-excited tooth to diagnose the state of the tooth. A nanosecond laser pulse (355 nm, 5 ns) was used as an ablating pulse and the sodium (3s2S–3p2P) at 588.99 and (3s2S–3p2P) at 589.99 nm, strontium (5s21S–1s5P) at 460.55 nm, and calcium (3d3D–4f 3F0) at 452.55 nm transitions for spectroscopic analysis. The spectroscopic observations in conjunction with discriminate analysis showed that calcium attached to the hydroxyapatite structure of the tooth was affected severely at the infected part of the tooth. The position-time plots generated from two-dimensional (2D) images conclusively showed a decrease in calcium concentration in the infected region of the irradiated tooth. Using the technique, we could distinguish between the healthy and carious parts of the tooth with significant accuracy.
We have investigated the atomic structure of graphene oxide by DFT calculations. Our spin restric... more We have investigated the atomic structure of graphene oxide by DFT calculations. Our spin restricted ab-initio density functional calculations have shown that the oxygen link to the graphene basal plane using epoxide bonds. The flat graphene sheets are found to deform by buckling due to formation of C -- O -- C linkages normal to the plane of the graphene sheets. The calculations were compared with x-ray diffraction and x-ray spectroscopic measurements. Tentative models of the structure are proposed based on the combined DFT and experimental data.
Applied Surface Science, 2007
We report formation of colloidal suspension of zinc oxide nanoparticles by pulsed laser ablation ... more We report formation of colloidal suspension of zinc oxide nanoparticles by pulsed laser ablation of a zinc metal target at room temperature in different liquid environment. We have used photoluminescence, atomic force microscopy and X-ray diffraction to characterize the nanoparticles. The sample ablated in deionized water showed the photoluminescence peak at 384 nm (3.23 eV), whereas peaks at 370 nm (3.35 eV) were observed for sample prepared in isopropanol. The use of water and isopropanol as a solvent yielded spherical nanoparticles of 14–20 nm while in acetone we found two types of particles, one spherical nanoparticles with sizes around 100 nm and another platelet-like structure of 1 μm in diameter and 40 nm in width. The absorption peak of samples prepared in deionized water and isopropanol are seen to be substantially blue shifted relative to that of the bulk zinc oxide due to the strong confinement effect. The technique offers an alternative for preparing the nanoparticles of active metal.
Plasmonic nanostructures can be tuned by changing their geometry such as the aspect ratio of gold... more Plasmonic nanostructures can be tuned by changing their geometry such as the aspect ratio of gold pillars. Although they are very attractive for many applications such as biosensors, imaging beyond diffraction limit etc. there is lack of an easy, cost-effective process for implementing such structures. We report a simple, facile and manufacturable method to produce gold-polymer plasmonic nanoarrays in nanoporous alumina templates. Two dimensional arrays of gold-polymer nanocomposite support discrete plasmon resonance modes at visible and infrared frequencies. Finite element full-wave analysis in three-dimensional computational domain confirms our experimental results.
Applied Physics Letters, 2011
The local atomic structure of graphene oxide has been probed using synchrotron radiations. Detail... more The local atomic structure of graphene oxide has been probed using synchrotron radiations. Detailed investigations of recently proposed simplistic model of graphene oxide using x-ray absorption near edge spectroscopy have been performed. X-ray diffraction measurements and calculations indicate loss of coherence between graphene-like layers. However, larger in-plane structural coherence is understood to be present. Selected area electron diffraction measurements indicate the presence of graphitic regions in graphene oxide which is expected to produce interesting confinement effects in graphene oxide which could be important for the development of tunable electronic and photonic devices.
Journal of Physical Chemistry C, 2010
Journal of Physical Chemistry Letters, 2010
Acs Applied Materials & Interfaces, 2010
Medical Engineering & Physics, 2008
We report on the elemental composition of healthy and infected part of human tooth using laser in... more We report on the elemental composition of healthy and infected part of human tooth using laser induced breakdown spectroscopy (LIBS). We have used prominent constituent transitions in laser-excited tooth to diagnose the state of the tooth. A nanosecond laser pulse (355 nm, 5 ns) was used as an ablating pulse and the sodium (3s2S–3p2P) at 588.99 and (3s2S–3p2P) at 589.99 nm, strontium (5s21S–1s5P) at 460.55 nm, and calcium (3d3D–4f 3F0) at 452.55 nm transitions for spectroscopic analysis. The spectroscopic observations in conjunction with discriminate analysis showed that calcium attached to the hydroxyapatite structure of the tooth was affected severely at the infected part of the tooth. The position-time plots generated from two-dimensional (2D) images conclusively showed a decrease in calcium concentration in the infected region of the irradiated tooth. Using the technique, we could distinguish between the healthy and carious parts of the tooth with significant accuracy.
We have investigated the atomic structure of graphene oxide by DFT calculations. Our spin restric... more We have investigated the atomic structure of graphene oxide by DFT calculations. Our spin restricted ab-initio density functional calculations have shown that the oxygen link to the graphene basal plane using epoxide bonds. The flat graphene sheets are found to deform by buckling due to formation of C -- O -- C linkages normal to the plane of the graphene sheets. The calculations were compared with x-ray diffraction and x-ray spectroscopic measurements. Tentative models of the structure are proposed based on the combined DFT and experimental data.
Applied Surface Science, 2007
We report formation of colloidal suspension of zinc oxide nanoparticles by pulsed laser ablation ... more We report formation of colloidal suspension of zinc oxide nanoparticles by pulsed laser ablation of a zinc metal target at room temperature in different liquid environment. We have used photoluminescence, atomic force microscopy and X-ray diffraction to characterize the nanoparticles. The sample ablated in deionized water showed the photoluminescence peak at 384 nm (3.23 eV), whereas peaks at 370 nm (3.35 eV) were observed for sample prepared in isopropanol. The use of water and isopropanol as a solvent yielded spherical nanoparticles of 14–20 nm while in acetone we found two types of particles, one spherical nanoparticles with sizes around 100 nm and another platelet-like structure of 1 μm in diameter and 40 nm in width. The absorption peak of samples prepared in deionized water and isopropanol are seen to be substantially blue shifted relative to that of the bulk zinc oxide due to the strong confinement effect. The technique offers an alternative for preparing the nanoparticles of active metal.