Synthesis and optical properties of CdTe nanocrystals with improved optical properties

CdTe nanocrystals are prepared by hydrothermal route using the reaction between Cd2+ and KHTe in the presence of thioglycolic acid as the stabilizing agent. Hydrothermal synthesis under optimum conditions resulted in a rapid growth. CdTe nanocrystals with high PL intensity and narrow PL spectra are obtained in less time. The growth mechanism of CdTe nanocrystals is investigated. The growth rate in the initial stage of synthesis is higher in hydrothermal synthesis resulting in an increased growth in diffusion controlled focused region

Highly Sensitive NO2 Detection and DMP Sensing at Room Temperature using Flexible SWNT Thick Film Sensor

  Low cost; easy to fabricate and flexible single wall carbon nanotubes thick film resistor (SWNT-TFR) for detailed study of NO2 detection is reported. SWNT-TFR was fabricated by vacuum filtration technique on flexible polycarbonate membrane. SWNT-TFR sensor shows selective response to NO2. The response increases from 1.47 per cent to 17.34 per cent with increasing the NO2 concentration from 0.2 ppm to 10 ppm, respectively. Different energy sources, IR, thermal and UV were explored for achieving fast recovery of the SWNT-TFR sensor. The results showed that the gas sensor gives immediate and fast recovery in the presence of UVC light. The calculated detection limit is less than 764 ppt for NO2. We are also presenting sensing of dimethyl methylphosphonate (DMMP) as a simulant of sarin. SWNT-TFR gives repeatable response of ~2.7 per cent for 500 ppm of DMMP. This work suggests the possibility to utilise SWNTs-TFR as NO2 sensors for air-quality monitoring.

Improved electrical parameter of graphene in Si/SiO2/Al2O3/graphene heterostructure for THz modulation

We proposed the extraction of necessary electrical parameters of graphene (Gr) on Si/SiO _2 /Gr and Si/SiO _2 /Al _2 O _3 /Gr heterostructure THz modulators using the THz measurement technique. The obtained average THz absorption is 24.5% more on Si/SiO _2 /Al _2 O _3 /Gr as compared to the Gr on Si/SiO _2 . The calculated value of the carrier mobility of graphene on Si/SiO _2 /Al _2 O _3 is 2.33 times more than that on Si/SiO _2 . The presence of Al _2 O _3 may play a role of a barrier for diffusion of trap and impurity charges from Si/SiO _2 to graphene which may lead to higher mobility and higher THz absorption. THz modulation measurements by optical pumping were also performed. Maximum modulation depth was 18.54% on Si/SiO _2 /Al _2 O _3 /Gr modulator at 2W pumping power which is 16.54% higher as compared to Gr on Si/SiO _2 . This shows that graphene on Si/SiO _2 /Al _2 O _3 heterostructure exhibits great potential for the development of an efficient electro-optical THz modulator as compared to Si/SiO _2 /Gr modulator

Effect of substrate bias in nitrogen incorporated amorphous carbon films with embedded nanoparticles deposited by filtered cathodic jet carbon arc technique

The properties of nitrogen incorporated amorphous carbon (a-C: N) films with embedded nanoparticles, deposited using a filtered cathodic jet carbon arc technique, are reported. X-ray diffraction, high resolution transmission electron microscope and Raman spectroscopy measurements reveal an amorphous structure, but on closer examination the presence of clusters of nanocarbon single crystals with d-spacing close to diamond cubic-phase have also been identified. The effect of substrate bias on the microstructure, conductivity, activation energy, optical band gap, optical constants, residual stress, hardness, elastic modulus, plastic index parameter, percentage elastic recovery and density of states of a-C: N films have been studied and the properties obtained are found to depend on the substrate bias