Keywords : Raman spectroscopy

Electroless deposition of nickel on biocompatible poly(dimethylsiloxane) after a laser processing as a pretreatment

Stephan Armyanov; Eugenia Valova; Konstantin Kolev; Dragomir Tatchev; Petar Atanasov; Nadya Stankova

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 101-106
DOI: 10.5185/amlett.2018.1818

Due to its biocompatibility poly(dimethylsiloxane) (PDMS) is an important material for the development of microelectromechanical systems or long-term, medical implants. The paper describes the morphology modifications and surface chemistry of PDMS during pulse laser treatment. SEM, μ-Raman spectroscopy, X-ray micro-tomography and XPS analyses are applied. PDMS decomposition takes place as a function of laser energy absorption. This leads to different oxidation degree of silicon, as shown by the curve fitting of Si 2p and O 1s. The irradiated parts become hydrophilic in contrast with the rest of the material, which remains hydrophobic. This is the condition enabling successful selective electroless deposition of Ni in the tracks, excluding the usual preceding sensibilization and chemical activation. This process is accomplished successfully after femtosecond laser irradiation and it is found that the time interval between laser treatment and metallization is not a critical parameter.

Optical, Electrical And Antimicrobial Studies Of Chemically Synthesized Graphite Oxide And Reduced Graphene Oxide

Alpana Thakur; Sunil Kumar; Manjula Sharma; V. S. Rangra

Advanced Materials Letters, 2016, Volume 7, Issue 12, Pages 1029-1034
DOI: 10.5185/amlett.2016.6810

Graphite oxide (GO) and reduced graphene oxide (RGO) have been synthesized using chemical methods. Prepared graphite oxide and reduced graphene oxide were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. XRD patterns, Raman spectra and FTIR spectroscopy confirms significant structural changes while reducing GO to RGO. The obtained products were further analyzed for their optical and electrical properties using UV-Vis spectroscopy, photoluminescence spectroscopy and four-point probe. RGO has shown excellent electrical conductivity of 1.363×10 4 S/m. The bactericidal action of prepared GO and RGO was also studied against Escherichia coli and Staphylococcus aureus bacteria.

High Temperature Dielectric Relaxation And Impedance Spectroscopy Studies On BaBiO3 

Divyanshu Bhatnagar; Ratnamala Chatterjee

Advanced Materials Letters, 2016, Volume 7, Issue 8, Pages 604-609
DOI: 10.5185/amlett.2016.6236

BaBiO3 (BBO) particles were successfully synthesized through solid-state route, to provide better understanding of its transport properties, which is not well studied yet. X-ray diffraction (XRD) measurement confirmed that the particles were crystallized with monoclinic structure in single phase. The Raman spectrum of BBO sample revealed the existence of two different Bi sites (the octahedral BiO6/3 and the triangular pyramidal BiO4/2 cluster). Subsequently, the observation of low resolution and lattice scale imaging through high resolution transmission electron microscope (HRTEM) indicated the formation of monoclinic BBO particles of size ~ 50-60 nm. The ring pattern obtained from selected area electron diffraction (SAED) inveterate polycrystalline nature of the sample and calculated structural parameters well harmonized with XRD results. As expected, BBO showed semiconducting behavior with resistivity of ~ 3.8 kΩ-cm at room temperature along with an excellent NTC (negative temperature coefficient) thermistor characteristic. The dielectric measurements and impedance spectroscopy studies reveal that BBO exhibit two typical characteristics, i.e., diffuse phase transition and frequency dependent dielectric maxima, of relaxor oxides; with negative dielectric constant above 550 K.

Defect Analysis And Performance Evaluation Of P-type Epitaxial GaAs Layer On Ge Substrate For GaAs/Ge Based Advanced Device

Goutam Kumar Dalapati; Vignesh Suresh; Sandipan Chakraborty; Chandreswar Mahata; Yi Ren; Thirumaleshawara Bhat; Sudhiranjan Tripathy; Taeyoon Lee; Lakshmi Kanta Bera; Dongzhi Chi

Advanced Materials Letters, 2016, Volume 7, Issue 7, Pages 517-524
DOI: 10.5185/amlett.2016.6439

The structural defects and formation of native oxides during thermal treatment on p-type epitaxial-GaAs/Ge have been investigated using spectroscopic measurements and electrical characterization. The performance of epi-GaAs based device depends on the interface quality between epi-GaAs and gate oxide and structural quality of the epi-GaAs layer. P-type epitaxial-GaAs was grown on Ge substrate using MOCVD technique at 675oC. Defective surface native oxides of arsenic and gallium oxides are observed for as-grown epi-GaAs layer. The arsenic oxide significantly reduced after thermal treatment as seen from XPS observations. The structural defects at surface enhanced after thermal treatment which is clearly probed by micro-Raman spectroscopy. Atomic layer deposited (ALD) Al2O3 significantly improved the interface properties after thermal treatment compared with bare epi-GaAs layer. Even though, the interface trap defect density slightly higher for p-type epi-GaAs MOS capacitor compared with bulk p-type GaAs devices, high frequency-dispersion in epi-GaAs based devices observed. This is mainly governs through the formation of p-i-n junction diode in the epi-GaAs layer on Ge substrates.

Mechanisms Of Composite-hydroxide-mediated Approach For The Synthesis Of Functional ZnO Nanostructures And Morphological Dependent Optical Emissions

Taj Muhammad Khan; M. Zakria; Rana I. Shakoor; M. Raffi; Mushtaq Ahmad

Advanced Materials Letters, 2015, Volume 6, Issue 7, Pages 592-599
DOI: 10.5185/amlett.2015.5876

We report synthesis of the functional ZnO nanostructures (nanowires, nanorods) by a cost-effective and efficient method; called composite-hydroxide-mediated (CHM) approach. Effect of the processing temperature on the particle size, morphology, and subsequently morphological dependent optical emissions is investigated. Needle-shaped nanowires are obtained at 200 and 220 o C, of about (500-1500) nm in length, while at 250 o C; nanorods are formed with length in the range of (200-460) nm and width (10-30) nm. Optical study reveals that ZnO nanorods show only ultra-violet (UV) emission while bent nanowires demonstrate both UV and green emissions simultaneously. The week green emission at 2.4 eV indicates no efficient trapping of the photo-generated hole in the nanostructures. Phase purity, crystalline structure, size and chemical nature of the product are probed by XRD, EDX, Raman spectroscopy and FT-IR. The particle size estimated from the spatial correlation phonon confinement model for the E2 (high) phonon mode. The applied approach is believed to be efficient, and a direct route for the synthesis of a wide range of simple and complex oxide nanostructures for novel electro-optical nanodevices.

Oxidative Synthesis And Electrochemical Studies Of Poly(aniline-co-pyrrole)-hybrid Carbon Nanostructured Composite Electrode Materials For Supercapacitor

Ashok Kumar Sharma; Preetam Bhardwaj; Sundeep Kumar Dhawan; Yashpal Sharma

Advanced Materials Letters, 2015, Volume 6, Issue 5, Pages 414-420
DOI: 10.5185/amlett.2015.5690

A novel study on conducting polymers based composites involving hybrid carbon nanostructure assemblage of graphene, amine functionalized multiwalled carbon nanotubes and poly(aniline-co-pyrrole) has been done. The composites were synthesized by oxidative polymerization of 1:1 mixture of aniline and pyrrole monomer with ammonium per sulphate and ferric chloride oxidants. UV-vis Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy were used to identify the chemical structure of the obtained composites. Thermal studies indicate that the composites are stable in comparison to poly (aniline-co-pyrrole) alone showing that the hybrid carbon assemblage contributes towards thermal stability in the composites. Crystalline properties of the composites were investigated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to characterize the surface morphology of the composites. The specific capacitance of the composites was characterized by cyclic voltammogram (CV). The capacitive studies reveal that the composite has synergistic effect and highest specific capacitance of 337.35F/g at scan rate of 10mV/sec and 193.06F/g at scan rate of 50 mV/sec was obtained for the composite having thinnest layer of co-polymer over hybrid carbon assemblage i.e., 02-PANI-co-PPY-C.

Structural Analysis By Rietveld Method And Its Correlation With Optical Propertis Of Nanocrystalline Zinc Oxide

Vikash Kumar; Swati Kumari; Pawan Kumar; Manoranjan Kar; Lawrence Kumar

Advanced Materials Letters, 2015, Volume 6, Issue 2, Pages 139-147
DOI: 10.5185/amlett.2015.5632

The correlation between structural and optical properties of nanocrystalline ZnO synthesized by the citrate precursor method has been investigated. The Rietveld refinement of X-ray diffraction pattern confirms the P63mc space group and formation of single phase hexagonal wurtzite structure with presence of tensile strain at the lattice site. The presence of Raman active optical phonon mode at 436 cm -1 which is a significant character of ZnO with hexagonal wurtzite structure supports the XRD result. FE-SEM result shows that the size of the particle is about 20 nm with nearly spherical shapes. The optical band gap energy at room temperature has been calculated as 3.28 eV using the Tauc plot technique. The UV-Vis sub-gap absorption curve supports the presence of strain inside the crystal. The photoluminescence spectrum indicates the dominancy of the defect related deep level or trap state emissions over the near band edge UV emissions using an excitation wavelength of 320 nm.

Structural And Optical Study Of MeV Cobalt Ion Implanted Silicon

Pramita Mishra; Vanaraj Solanki; Ashutosh Rath; Soumee Chakraborty; Himanshu Lohani; Pratap K. Sahoo; Biju Raja Sekhar

Advanced Materials Letters, 2014, Volume 5, Issue 12, Pages 699-705
DOI: 10.5185/amlett.2014.nib503

We report the optical tunability through defect states created in silicon by 1 MeV cobalt ion implantation at room temperature in the fluence range of 5 × 10 13 to 5 × 10 15 ions cm -2 . Atomic force microscopy studies reveal the surface nanostructures with maximum roughness of 0.9 nm at a critical fluence of 5 × 10 15 ions cm-2 which is reduced to 0.148 nm with further increase of fluence. The enhanced native oxide layers after Co ion implantation observed from X-Ray photoelectron spectroscopy studies confirm the presence of surface defects. The combined effect of nanostructures formation and amorphization leads to band gap tailoring. For low fluence, the nanostructures produced on the surface result in an enhanced absorption in the entire UV-Visible region with a simultaneous reduction in band gap of 0.2 eV in comparison to pristine Si whereas high fluence implantation results in interference fringes which signifies the enhancement in refractive index of the top implanted layer ensuing increase in band gap of 0.3 eV. Combined amorphous and crystalline phases of nanostructured surface with tunable optical absorption may have potential applications in solar cell, photovoltaics and optical sensors.

High Stability Field Emission From Zinc Oxide Coated Multiwalled Carbon Nanotube Films

Rajkumar Patra; Santanu Ghosh; Himani Sharma; Vasant D. Vankar

Advanced Materials Letters, 2013, Volume 4, Issue 11, Pages 849-855
DOI: 10.5185/amlett.2013.4465

A comparative study of electron field emission (FE) property of pristine mutiwalled carbon nanotubes (p-CNTs), zinc (Zn) coated CNTs (Zn-CNT), zinc oxide (ZnO) coated CNTs (ZnO-CNT) is reported. CNTs were synthesized on p-type Si (100) by microwave plasma enhanced chemical vapor deposition (MPECVD) method and the sample was divided into three parts. On two of these parts, a thin layer (~ 4nm) of Zn film was deposited. One of these (Zn-CNT) was kept for analysis and the other one was annealed in oxygen (O2) atmosphere at 520° C for 60 minutes to get ZnO coated CNT film (ZnO-CNT). Scanning electron microscope (SEM) analysis confirmed CNT formation as well as Zn and ZnO coating on the top of p-CNT films. Further, energy-dispersive X-ray spectroscopy (EDX) results confirmed the presence of zinc and oxygen in these two samples. A detailed field emission study performed in these films give following results: (i) lowest turn-on field (electric field required to produce 10 μA/cm 2 current density) and threshold fields (electric field required to produce 100 μA/cm 2 current density) for pristine sample (3.3 V/μm and 5.1 V/μm respectively), followed by ZnO-CNT sample (3.7 V/μm and 6.3 V/μm respectively); (ii) highest temporal stability in current density versus field (J-E characteristics) in ZnO-CNT film as compared to other two, (iii) highest field enhancement factor in ZnO-CNT films as compared to other two. The FE results are correlated with microstructures of the samples as revealed by micro-Raman spectroscopy and transmission electron microscopy (TEM) studies.

Swift Heavy Ion Irradiation Induced Structural, Optical And Conformational Modifications In Conducting Polymer Nanostructures

A. Kumar;Somik Banerjee

Advanced Materials Letters, 2013, Volume 4, Issue 6, Pages 433-437
DOI: 10.5185/amlett.2012.ib.109

Structural and conformational modifications in conducting polymer nanostructures viz., Polyaniline (PAni) nanofibers induced by swift heavy ion (SHI) irradiation have been investigated employing TEM, XRD, UV-Vis, FTIR and micro-Raman spectroscopy. Upon interaction with the highly energetic ions, PAni nanofibers are fragmented and get amorphized. The local range of order is found to decrease with a corresponding increase in the concentration of point defects and dislocations leading to the enhancement in strain. Vibrational spectra of the pristine and SHI irradiated PAni nanofibers studied using FTIR and micro-Raman (μR) spectroscopy indicate conformational changes in PAni nanofibers upon SHI irradiation. Loss of π-stacking due to the enhancement in the torsion angle between Cring-N-Cring upon irradiation is indicative of strong electrostatic interaction between the electron rich C-N site in the aromatic rings of PAni chains and the ion beam. The most significant variation in PAni nanofibers upon SHI irradiation is the transformation of para di-substituted benzene (benzenoid) structure of PAni into the quinone di-imine (quinoid) structures; a phenomenon that has been simultaneously observed in both the FTIR and Raman spectra. The presence of two main peaks representing the same structures in PAni nanofibers in both the Raman and IR spectra is because of the presence of delocalized sp2 phases and local disorder in PAni nanofibers, which gives rise to electrical and mechanical fluctuations that destroy the symmetry rules.

Fabrication Of Polyaniline Nanofibers By Chronopotentiometery

Yasir Ali; R G Sonkawade;A S Dhaliwal; Vijay Kumar

Advanced Materials Letters, 2012, Volume 3, Issue 5, Pages 388-392
DOI: 10.5185/amlett.2012.6358

We have electrochemically synthesized polyaniline nano fibers with optimized process parameters (viz. concentration of monomer and dopant, applied current density, deposition time, etc.) on ITO coated glass substrate. The nano fibers of polyaniline were subjected to UV Visible, SEM and Raman spectroscopy. UV Vis spectra show two prominent peaks at 317 and 418 nm, which confirm the presence of different forms of polyaniline. Raman spectra confirm the formation of polyaniline. SEM image of synthesized nano fibers showed a flower like structure with an isotropic growth rate.

Influence Of ZnO Buffer Layer On Growth Of Sb Doped ZnO Nano Wires Using Nano Particle Assisted Pulsed Laser Deposition (NAPLD) Using Sb As Catalyst

I.A. Palani; D. Nakamura; K. Okazaki; T. Shimogaki; M. Higashihata; T. Okada

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 66-70
DOI: 10.5185/amlett.2012.1302

Influence of ZnO buffer layer thickness on the structural and optical properties of the Sb catalyzed/doped ZnO nanowires synthesized using NAPLD has been investigated. Buffer layer with a thickness of 100 nm, 800 nm and 1600 nm coated with Sb are used as a substrate and pure ZnO was used as a target to synthesize Sb doped ZnO nanowires. Introduction of the buffer layer lead to the growth of vertically aligned along with horizontally grown ZnO nano wires. With the increase in buffer layer thickness, the core diameter of the vertically grown ZnO nano wires was subsequently increased. Nano wires synthesized with a buffer layer thickness of 1600 nm showed a significant change in the lattice constants, resulting in measurable lower angle of about 0.06º from XRD, widening of lattice fringe spacing of 0.54 nm from TEM and Suppression of A1T and E1(L0) modes in Raman Spectroscopic. In addition a strong UV emission with absence of visible emission was observed from the room temperature PL. This confirms the generation of Sb doped ZnO nano wire with high crystal quality.

Assessing the conformational and cellular changes of ZnO nanoparticles impregnated Escherichia coli cells through molecular fingerprinting

Ranu K. Dutta; Prashant K. Sharma; Avinash C. Pandey

Advanced Materials Letters, 2011, Volume 2, Issue 4, Pages 268-275
DOI: 10.5185/amlett.indias.195

Here is an insight into the effects of interaction of ZnO nanoparticles and the various cellular level changes that are brought about by the help of Raman spectroscopy on individual Escherichia coli cells. Raman vibrational signatures show variation in peak intensities of some of the cellular components of E coli cells with increase in nanoparticles concentration. This can be attributed to the cellular and molecular changes associated with bacterial cell growth, as the cells proceed from lag phase to stationary phase, which indicates that ZnO interferences with bacterial growth. Growth kinetics studies show mitigation in growth and colony forming units (CFU) counts. Changes in cellular morphology as investigated by atomic force microscopy and scanning electron microscopy, show destruction and even rupture of cell wall at higher ZnO concentration. This study pertains to any alterations brought about at the cellular level, which may be extended to other nanomaterials in the environment and the effect on human cells as well.

Raman spectra of hot-pressed boron suboxide

Ronald Machaka; Bonex W. Mwakikunga; Elayaperumal Manikandan; Trevor E. Derry; Iakovos Sigalas

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 58-64
DOI: 10.5185/amlett.2010.9167

Despite hot pressing being the most popular method of consolidating B6O powder, the Raman spectrum of polycrystalline hot-pressed B6O was until now poorly understood. Yet, recent reports have contributed to the understanding of only high-pressure and high-temperature sintered B6O. Using an automated method for subtraction of the fluorescence background from Raman measurements, the first- and second-order Raman spectra of B6O and their dependence on the wavelength of the excitation line from a green Argon ion (Ar + ) laser are reported. Our results confirm the existence of observable highly resolved first- and second-order Raman modes measured at ambient conditions using a green Ar + ion laser as the source of excitation. We also extend our study to present a comparative analysis of our recovered first-order Raman spectra and previously reported first-order Raman spectra other α-rhombohedral boron type based ultra-hard boron-rich ceramic materials. The results show an overall good agreement.