Concentration-dependent optical properties of TGA stabilized CdTe Quantum dots synthesized via the single injection hydrothermal method in the ambient environment

Thioglycolic acid (TGA) stabilized aqueous CdTe Quantum dots (QDs) were synthesized using a facile, cost efficient Single Injection Hydrothermal (SIH) method. The complete preparation of precursors and growth of QDs was carried out in the ambient environment without inter gas protection. The Cadmium and Tellurium precursors were prepared from cadmium nitrate and elemental tellurium powder with sodium borohydride as reducing agent respectively. A systematic investigation was carried out in order to study the effect of 0.04M and 0.08M TGA concentration on ease synthesis, stability and size-tunable optical absorbance, bandgap, photoluminescence (PL) and Quantum yield (QY) of CdTe QDs. The Structure of QDs was verified by XRD and optical properties by absorbance and PL spectra. Experimental results revealed that the 0.08M TGA QDs possess good chemical and optical stability with high luminescence and decent QY, ready to use in optoelectronics, photovoltaic and biological application. © 2017 Elsevier Lt

Multiwalled carbon nanotube-based patch antenna for bandwidth enhancement

A novel carbon nanotube (CNT)-based rectangular microstrip antenna for wide impedance bandwidth applications has been designed and developed. The copper patch commonly placed on the substrate in a conventional rectangular microstrip antenna is replaced with a CNT patch prepared using spin coating. The MWCNT patch antenna was fabricated by spin coating method and it exhibits an increased impedance bandwidth of 20. The enhancement of the impedance bandwidth does not affect the broadside radiation characteristics. The carbon nanotubes are highly conductive nanomaterial. Due to this unique property, each nanotube present on the surface resonates electromagnetic waves individually and influences the enhancement in the bandwidth. The simple design and fabrication of the proposed antenna can be employed for synthetic aperture radar applications. © 2017 Elsevier B.V

Distribution and enrichment of 210Po in the environment of Kaiga in South India

Several soil and vegetation samples from the environment of Kaiga nuclear power plant site in the south western region of India were analysed for 210Po. The vertical profile, particle-size distribution, seasonal variation and the dry deposition rate of 210Po were measured employing the chemical method and α - counting technique. 210Po activity in soil varies from 17.1 to 228.2 Bq kg-1 with a mean value of 83.3 Bq kg-1. The activity of 210Po is higher in the surface soil (0-5 cm) and decreases as depth increases to 20 cm and remains nearly constant thereafter. The activity concentration is almost uniform in the grain sizes of 350-177 μm and below 177 μm. Pterobryopsis tumida (Hook.) Dix, a plant of the moss family, shows a very high level of 210Po activity - 2724 ± 13 Bq kg-1. Seasonal variation studies show elevated levels of 210Po in vegetation during winter. The annual dry deposition rate of 210Po was 53.4 Bq m-2 yr-1. (C) 2000 Elsevier Science Ltd

Optical and structural properties of radiant heated and vacuum annealed electron beam deposited CdS thin films

This paper describes the optical and structural properties of Cadmium Sulfide (CdS) thin films deposited onto glass substrate by vacuum evapn. assisted with (RH) and without radiant heater (VA)​. The RH and VA thin films showed high transmittance of 87​% at 680 and 550 nm resp. The optical band gap was estd. using transmittance measurements and found to be decreased with VA thin film. RH thin film revealed max. absorption coeff. compared to VA thin film. The XRD anal. confirmed that the films reveal hexagonal and cubic (002) orientations. The crystallite grain size was found to be 15.5 and 16.7 nm for RH and VA films resp

Temperature Dependent Optical and Morphological Properties of Sb2Te3 Thin Films

Sb2Te3 thin films of different temperature ranging from room temperature to 200°C were prepared on glass substrate by thermal evaporation method. The effects of temperature on optical and morphological properties of thin films were studied. AFM images indicated crystalline nature of Sb2Te3. The optical properties exhibited a decreasing trend of band gap from 1.24eV to 1.06eV with increase in temperature. Transmittance decreased as the temperature was increased and displayed no transmittance in the visible range at 200°C. Surface roughness decreased up to 150°C after which it increased

Cs-137 concentration in the environment of Kaiga of south west coast of India

This paper presents the results of Cs-137 activity in soil and vegetation obtained through a carefully planned pre-operational survey for the establishment of baseline data on background radiation level and distribution of radionuclides in the environment of Kaiga, in the south west coast of India, where two nuclear power reactors of 235 MWe each are under construction, The vertical profile in soil and the seasonal variation in the activity have been studied. Nine commonly available vegetation species of Kaiga region were analyzed for their Cs-137 activity, and the soil-to-plant transfer coefficients were evaluated. Measurements were made by gamma spectrometry method employing a 90 cc HpGe detector and a 3 x 3-inch well type NaI(TI) detector. Results show significant levels of Cs-137 activity in soil samples - ranging from below detection limit (BDL) to 65.4 Bq kg(-1). The mean value of activity observed in 0-5 cm soil profiles of Kaiga environs is significantly higher when compared to the reported values for other environs of India, Depth profile studies show that the Cs-137 activity decreases with the increasing soil depth, and it is below detection limit for depths more than 25 cm, The mean value of effective dose commitment due to the presence of Cs-137 in soil was 167.2 mu Sv. Vegetation samples of the region show elevated Levels of Cs-137 concentration. Epiphytic plants Cymbidium aloifolium (Lo.) Swartz, and Petrobryopsis tumida (Hook,) I)ix. have been identified as bio-indicators to monitor the fallout of this radionuclide in the environment of Kaiga, Seasonal variation studies indicate higher fallout of this radionuclide along with rain

Optical and structural properties of radiant heated and vacuum annealed electron beam deposited CdS thin films

This paper describes the optical and structural properties of Cadmium Sulfide (CdS) thin films deposited onto glass substrate by vacuum evapn. assisted with (RH) and without radiant heater (VA)​. The RH and VA thin films showed high transmittance of 87​% at 680 and 550 nm resp. The optical band gap was estd. using transmittance measurements and found to be decreased with VA thin film. RH thin film revealed max. absorption coeff. compared to VA thin film. The XRD anal. confirmed that the films reveal hexagonal and cubic (002) orientations. The crystallite grain size was found to be 15.5 and 16.7 nm for RH and VA films resp

A facile single injection Hydrothermal method for the synthesis of thiol capped CdTe Quantum dots as light harvesters

A facile, Single Injection Hydrothermal (SIH) method has been developed to synthesize high quality 3-​Mercaptopropionic Acid (MPA) stabilized aq. CdTe QDs, entirely in ambient environment. The synthesis protocol eliminates the use of inert atm. for reducing elemental Tellurium powder to Te precursor avoiding the oxidn. of Te powder. The XRD result revealed that the synthesized QDs are in cubic zincblende type cryst. structure, without signature of Te oxidn. FTIR spectra have confirmed the attachment of short chained org. compd. MPA to the surface of QDs by covalent bond. The Quantum confinement effect was clearly evident by shift in Longitudinal Optic (LO) peak of Raman spectra and absorption peak wavelength with respect to bulk CdTe materials. The optical direct band gap energy of CdTe QDs is between 3.63 eV to 1.96 eV and QDs size below 6 nm, confirm the QDs are well under strong Quantum confinement regime. Also, photoluminescence spectra depict a stable and high luminescence emission from green to dark red color. All these results corroborate that the synthesis of CdTe QDs procedure is very advantageous and present a simple, economical and easily up scalable method for large scale prodn

Optimization of thickness of Sb2Te3 thin film as back contact for CdTe thin film solar cells

Sb2Te3 thin films of different thickness ranging from 100 to 500 nm were prepd. on glass substrate by thermal evapn. method. The effects of thickness on structural, optical and elec. properties of thin films were studied. XRD revealed that grain size increases from 1.1nm to 98.7 nm with increase in film thickness. The internal strain and dislocation d. decreased with increase in film thickness. The optical band gap decreases from 1.3 to 0.9 eV with increase in film thickness. AFM images indicated cryst. nature of Sb2Te3. Surface roughness increased up to 400nm after which it decreased. The resistivity decreases with increase in thickness at room temp. ranging from 2.9×10-​3 to 1.35×10-​4 Ωcm. The work function and barrier height decreases as the film thickness increases from 5.45 to 5.05eV and barrier height from 0.3 to -​0.1eV. The results elucidate that Sb2Te3 back contact of 400 nm thickness is ideal and efficient to be used in CdTe solar cell

Transconductance and Transfer Characteristics of 8 MeV Electron Irradiated Dual N-Channel MOSFETs

The electrical characteristics of dual N-channel enhancement metal-oxide semiconductor field-effect transistors (MOSFETs) were altered by irradiating with 8 MeV electron beam for different doses ranging from 200 Gy to 1 kGy at ambient air. The irradiation experiments were conducted with gate bias (VGS = -2, 0, +1.5 and +2 V). Significant increase in transconductance (gm) was observed after irradiation. The gm was found to increase drastically for the dose of 1 kGy with positive bias (1.5 and 2 V). The transfer characteristics at VDS=12 V revealed that the drain current (ID) increases with the increase of dose and also increases with the increase of gate bias voltage during irradiation. The results of these investigations are presented and discussed