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We present results of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and energy-... more We present results of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and energy-dispersive X-ray (EDX) analysis of natural colorless topaz crystal of local Pakistani origin. Topaz plasma was produced in the ambient air using a nanosecond laser pulse of width 5 ns and wavelength 532 nm. For the purpose of detection of maximum possible constituent elements within the Topaz sample, the laser fluences were varied, ranging 19.6–37.6 J·cm−2 and optical emission from the plasma was recorded within the spectral range of 250–870 nm. The spectrum obtained has shown the presence of seven elements viz. Al, Si, F, O, H, Na and N. Results shows that the fluorine was detected at laser fluence higher than 35 J·cm−2 and plasma temperature of >1 eV. Al and Si were found as the major compositional elements in topaz crystals. The ratios of concentrations of Al and Si were found as 1.55 and 1.59 estimated by CF-LIBS and EDX, respectively. Furthermore, no impurity was found in the inv...
The current research aimed to evaluatein vitrobiological activities of green-synthesized silver n... more The current research aimed to evaluatein vitrobiological activities of green-synthesized silver nanoparticles using theAllium sativumclove extract. The stability of green-synthesized silver nanoparticles was evaluated via storage at 4°C, room temperature (37°C), and calcined at 300°C, 500°C, and 700°C. The antibacterial effect was evaluated using agar well, spread plate, biofilm reduction, and cell proliferation inhibition assays. The cytotoxic and antidiabetic effects were determined via brine shrimp lethality, protein kinase inhibition, and α-amylase inhibition assays. DPPH scavenging, iron-chelating, anticoagulant, and hemolytic effects were evaluated. The highest inhibition ofKlebsiella pneumoniaewas observed when freshly prepared, calcined (300°C), and stored nanoparticles (4°C and 37°C) were applied (9.66, 9.55, 7.33, and 6.65 mm) against freshly prepared and calcined at 700°C which showed the highest inhibition ofPseudomonas aeruginosa(8.55 and 7.66 mm). Cell viability assay,...
This article presents elemental analysis of an economically important mineral (chalcopyrite) of l... more This article presents elemental analysis of an economically important mineral (chalcopyrite) of local origin. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) methodology based on the assumption of optically thin plasma and local thermodynamic equilibrium was employed for quantitative analysis. Plasma on the surface of the chalcopyrite target was generated by an Nd:YAG laser beam of wavelength 532 nm, pulse width 5 ns, and operated at repetition rate of 10 Hz. A LIBS2000+ detection system, comprised of five spectrometers, covering the spectral range from 200–720 nm, was used to record the signal of the optical emission from the chalcopyrite plasma. Recorded optical spectrum revealed the presence of Cu and Fe as the major elements while Ca and Na were recognized as the minor elements in the target sample. Quantitative analysis has shown that the relative concentrations of Cu, Fe, and Ca in the sample under study were 58.9%, 40.2%, and 0.9% by weight respectively. Howev...
Laser based efficient new nanofabrication methods with technical feasibility for the fast uptake ... more Laser based efficient new nanofabrication methods with technical feasibility for the fast uptake in industrial application are of significant global demand. A recent simplest approach in this way is the standard pulsed laser deposition (PLD), used since 1960s after the development of high power lasers. Over all, PLD is a fit method towards the preparation of a variety of nanomaterials only for research purpose. Nevertheless, the method is relatively slow and could not adopted in industrial scale application. A recent new-fangled development in this direction is the atmospheric-PLD (APLD), where ablation of the target by a laser pulse occurs at atmospheric gas pressure and the ablated material is delivered to the substrate using a flowing medium such as gas or atmospheric plasma. With this method, a variety of nanomaterials such as plasmonic metal NP film could be produced for practical ap
For further uptake in the solar cell industry, n-ZnO/p-Si single heterojunction solar cell has at... more For further uptake in the solar cell industry, n-ZnO/p-Si single heterojunction solar cell has attracted much attention of the research community in recent years. This paper reports the influence of bandgap and/or electron affinity tuning of zinc oxide on the performance of n-ZnO/p-Si single heterojunction photovoltaic cell using PC1D simulations. The simulation results reveal that the open circuit voltage and fill factor can be improved significantly by optimizing valence-band and conduction-band off-sets by engineering the bandgap and electron affinity of zinc oxide. An overall conversion efficiency of more than 20.3% can be achieved without additional cost or any change in device structure. It has been found that the improvement in efficiency is mainly due to reduction in conduction band offset that has a significant influence on minority carrier current.
Cd1−xZnxS thin films of variable compositions (x = 0.2, 0.4, 0.6, 0.8) were deposited on glass at... more Cd1−xZnxS thin films of variable compositions (x = 0.2, 0.4, 0.6, 0.8) were deposited on glass at room temperature by thermal evaporation process. The prepared samples were annealed at two different temperatures (300 °C, 400 °C) for 1 hour in ambient air. The effects of post-annealing on the structural and optical characteristics were investigated using X-ray diffraction (XRD), spectrophotometry, and Raman spectroscopy (RS) methods. XRD studies suggested that the annealed and as-deposited samples belong to wurtzite structure for all Zn concentrations with a preferential orientation along (002) plane. Spectrophotometry analysis of the samples revealed that the energy band gap decreased with annealing temperature. RS investigated different phonon bands and crystalline phases. Two longitudinal optical phonon modes (1-LO, 2-LO) corresponding to monophase hexagonal structure were observed for all Cd1−xZnxS samples. The observed red-shift and anti-symmetrical nature of the 1-LO phonon mod...
Dielectric-barrier-discharge (DBD) plasma jets provide viable state-of-the-art nonthermal process... more Dielectric-barrier-discharge (DBD) plasma jets provide viable state-of-the-art nonthermal processes for a wide range of nanomaterials including particle transport and deposition. We report the interaction of argon and helium plasma jets with the particle aerosol, produced by ns laser ablation of a silver target and subsequently their transport for deposition on a distant substrate. The nanofeatures and functionality of the nanoparticles, entrained and deposited with the two plasma jets were compared using high-resolution electron microscopy, helium ion microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, and in terms of the SERS effect. The plasma jet facilitates the transport of the particle aerosol under the upshot of plasma ionic wind, caused by the high electric field in the plasma. Compared to the helium plasma jet, the argon plasma jet leads to a relatively large particle deposition and promotes the formation of aggregates. The helium plasma jet enabled ...
We present results of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and energy-... more We present results of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and energy-dispersive X-ray (EDX) analysis of natural colorless topaz crystal of local Pakistani origin. Topaz plasma was produced in the ambient air using a nanosecond laser pulse of width 5 ns and wavelength 532 nm. For the purpose of detection of maximum possible constituent elements within the Topaz sample, the laser fluences were varied, ranging 19.6–37.6 J·cm−2 and optical emission from the plasma was recorded within the spectral range of 250–870 nm. The spectrum obtained has shown the presence of seven elements viz. Al, Si, F, O, H, Na and N. Results shows that the fluorine was detected at laser fluence higher than 35 J·cm−2 and plasma temperature of >1 eV. Al and Si were found as the major compositional elements in topaz crystals. The ratios of concentrations of Al and Si were found as 1.55 and 1.59 estimated by CF-LIBS and EDX, respectively. Furthermore, no impurity was found in the inv...
The current research aimed to evaluatein vitrobiological activities of green-synthesized silver n... more The current research aimed to evaluatein vitrobiological activities of green-synthesized silver nanoparticles using theAllium sativumclove extract. The stability of green-synthesized silver nanoparticles was evaluated via storage at 4°C, room temperature (37°C), and calcined at 300°C, 500°C, and 700°C. The antibacterial effect was evaluated using agar well, spread plate, biofilm reduction, and cell proliferation inhibition assays. The cytotoxic and antidiabetic effects were determined via brine shrimp lethality, protein kinase inhibition, and α-amylase inhibition assays. DPPH scavenging, iron-chelating, anticoagulant, and hemolytic effects were evaluated. The highest inhibition ofKlebsiella pneumoniaewas observed when freshly prepared, calcined (300°C), and stored nanoparticles (4°C and 37°C) were applied (9.66, 9.55, 7.33, and 6.65 mm) against freshly prepared and calcined at 700°C which showed the highest inhibition ofPseudomonas aeruginosa(8.55 and 7.66 mm). Cell viability assay,...
This article presents elemental analysis of an economically important mineral (chalcopyrite) of l... more This article presents elemental analysis of an economically important mineral (chalcopyrite) of local origin. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) methodology based on the assumption of optically thin plasma and local thermodynamic equilibrium was employed for quantitative analysis. Plasma on the surface of the chalcopyrite target was generated by an Nd:YAG laser beam of wavelength 532 nm, pulse width 5 ns, and operated at repetition rate of 10 Hz. A LIBS2000+ detection system, comprised of five spectrometers, covering the spectral range from 200–720 nm, was used to record the signal of the optical emission from the chalcopyrite plasma. Recorded optical spectrum revealed the presence of Cu and Fe as the major elements while Ca and Na were recognized as the minor elements in the target sample. Quantitative analysis has shown that the relative concentrations of Cu, Fe, and Ca in the sample under study were 58.9%, 40.2%, and 0.9% by weight respectively. Howev...
Laser based efficient new nanofabrication methods with technical feasibility for the fast uptake ... more Laser based efficient new nanofabrication methods with technical feasibility for the fast uptake in industrial application are of significant global demand. A recent simplest approach in this way is the standard pulsed laser deposition (PLD), used since 1960s after the development of high power lasers. Over all, PLD is a fit method towards the preparation of a variety of nanomaterials only for research purpose. Nevertheless, the method is relatively slow and could not adopted in industrial scale application. A recent new-fangled development in this direction is the atmospheric-PLD (APLD), where ablation of the target by a laser pulse occurs at atmospheric gas pressure and the ablated material is delivered to the substrate using a flowing medium such as gas or atmospheric plasma. With this method, a variety of nanomaterials such as plasmonic metal NP film could be produced for practical ap
For further uptake in the solar cell industry, n-ZnO/p-Si single heterojunction solar cell has at... more For further uptake in the solar cell industry, n-ZnO/p-Si single heterojunction solar cell has attracted much attention of the research community in recent years. This paper reports the influence of bandgap and/or electron affinity tuning of zinc oxide on the performance of n-ZnO/p-Si single heterojunction photovoltaic cell using PC1D simulations. The simulation results reveal that the open circuit voltage and fill factor can be improved significantly by optimizing valence-band and conduction-band off-sets by engineering the bandgap and electron affinity of zinc oxide. An overall conversion efficiency of more than 20.3% can be achieved without additional cost or any change in device structure. It has been found that the improvement in efficiency is mainly due to reduction in conduction band offset that has a significant influence on minority carrier current.
Cd1−xZnxS thin films of variable compositions (x = 0.2, 0.4, 0.6, 0.8) were deposited on glass at... more Cd1−xZnxS thin films of variable compositions (x = 0.2, 0.4, 0.6, 0.8) were deposited on glass at room temperature by thermal evaporation process. The prepared samples were annealed at two different temperatures (300 °C, 400 °C) for 1 hour in ambient air. The effects of post-annealing on the structural and optical characteristics were investigated using X-ray diffraction (XRD), spectrophotometry, and Raman spectroscopy (RS) methods. XRD studies suggested that the annealed and as-deposited samples belong to wurtzite structure for all Zn concentrations with a preferential orientation along (002) plane. Spectrophotometry analysis of the samples revealed that the energy band gap decreased with annealing temperature. RS investigated different phonon bands and crystalline phases. Two longitudinal optical phonon modes (1-LO, 2-LO) corresponding to monophase hexagonal structure were observed for all Cd1−xZnxS samples. The observed red-shift and anti-symmetrical nature of the 1-LO phonon mod...
Dielectric-barrier-discharge (DBD) plasma jets provide viable state-of-the-art nonthermal process... more Dielectric-barrier-discharge (DBD) plasma jets provide viable state-of-the-art nonthermal processes for a wide range of nanomaterials including particle transport and deposition. We report the interaction of argon and helium plasma jets with the particle aerosol, produced by ns laser ablation of a silver target and subsequently their transport for deposition on a distant substrate. The nanofeatures and functionality of the nanoparticles, entrained and deposited with the two plasma jets were compared using high-resolution electron microscopy, helium ion microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, and in terms of the SERS effect. The plasma jet facilitates the transport of the particle aerosol under the upshot of plasma ionic wind, caused by the high electric field in the plasma. Compared to the helium plasma jet, the argon plasma jet leads to a relatively large particle deposition and promotes the formation of aggregates. The helium plasma jet enabled ...
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Papers by Taj Khan