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Taj Khan

Trinity College Dublin, School of Physics, Graduate Student

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I am a very determined and highly motivated person. I am constantly looking for innovative research and development and take my job seriously. I like to see things in wide perspective and believe I'm quite easy-going to work with. I relish a challenge.

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Papers by Taj Khan

Synthesis and optical study of heat-treated ZnO nanopowder for optoelectronic applications

Bulletin of Materials Science, 2015

Smart integration of cold plasma stream and surface discharge with ns laser ablation for composite nanomaterial

Discover Nano, May 27, 2024

Applications of DBD plasma jets in the advanced nanomaterials and COVID-19 pandemic

Elsevier eBooks, 2022

Chemical Analysis of Thermoluminescent Colorless Topaz Crystal Using Laser-Induced Breakdown Spectroscopy

Minerals, 2021

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...

In vitro bactericidal, antidiabetic, cytotoxic, anticoagulant, and hemolytic effect of green-synthesized silver nanoparticles using Allium sativum clove extract incubated at various temperatures

Green Processing and Synthesis, 2020

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,...

Compositional Analysis of Chalcopyrite Using Calibration-Free Laser-Induced Breakdown Spectroscopy

Applied Sciences, 2020

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...

Quantification of elemental composition of Granite Gneiss collected from Neelum Valley using calibration free laser-induced breakdown and energy-dispersive X-ray spectroscopy

Journal of Radiation Research and Applied Sciences, 2020

Calibrationfree laser-induced breakdown spectroscopy (CF-LIBS) has been employed for elemental an... more Calibrationfree laser-induced breakdown spectroscopy (CF-LIBS) has been employed for elemental analysis of Granite Gneiss, rock sample, collected from Neelum Valley of Azad Jammu & Kashmir, Pakistan. The sample was irradiated with focused laser beam from Q-switched Neodymium Yttrium Aluminum Garnet laser, having 532 nm wavelength and pulse width of 5 ns, and the emission spectrum was recorded with a spectrometer. Overall, ten elements viz. Si, Al, K, Fe, Sr, Ca, Mg, Na, Li, and H were identified by inspecting the characteristic emission lines. Out of ten detected elements, seven elements fulfilling the criteria of calibration-free technique, namely: Si, Al, K, Fe, Sr, Ca, and Mg, were quantified. Sample was also analyzed by employing energydispersive X-ray spectroscopy (EDX) and the results confirmed the presence of all those elements in the sample that were detected by LIBS, except Li and H. For the most abundant element Si in the Granite Gneiss sample, a significant agreement of two techniques for the quantitative results is obtained. Both the techniques have confirmed that Granite Gneiss consists mainly of Si with abundance of 72.75% and 71.30% by weight as measured by CF-LIBS and EDX, respectively. Findings of study show that for the elements with minor concentrations, quantitative results as measured with both techniques were not in close agreement.

Atmospheric DBD Plasma Source in Play for SERS Active Substrates

Biomedical Journal of Scientific & Technical Research, 2019

High resolution SERS spectra has made possible to do multicomponent analysis simultaneously. This... more High resolution SERS spectra has made possible to do multicomponent analysis simultaneously. This has driven the production demand of SERS substrates by technically feasible methods for further uptake on industrial scale. Here, a new idea of combining an atmospheric DBD plasma with ablation process at atmospheric gas pressure, is floated and described. The out flow from a DBD source, developed in flowing argon or helium is used to drive the plasmonic NP aerosol, produced from ablation of silver or gold target. The NP aerosols carried with the plasma jet, directly land on the solid surface and act as "hot spots" and makes a SERS active substrate to directly use for detection purpose. It is expected that the interaction of the plasma jet with the substrate would lead to formation of different morphologies and peculiar structures, and magnitude of SERS enhancement. The proposed approach seems handy to make flexible SERS substrate such as paper and to use directly for a wide range chemical and biological detection.

Various pulsed laser deposition methods for preparation of silver-sensitised glass and paper substrates for surface-enhanced Raman spectroscopy

Applied Physics A, 2019

Silver nanoparticle films on glass and paper were prepared using vacuum pulsed laser deposition, ... more Silver nanoparticle films on glass and paper were prepared using vacuum pulsed laser deposition, and various methods of atmospheric pulsed laser deposition, where ablated material forms a nanoparticle aerosol near the target and is delivered in a gas flow to the substrate. The performance of the films for surface-enhanced Raman spectroscopy (SERS) was investigated using a 10-4 M aqueous solution of rhodamine 6G organic dye. The SERS sensitivity was quantified in terms of the apparent enhancement factor and the signal-to-noise ratio. For the films made by supersonic atmospheric pulsed laser deposition, the apparent enhancement factor was found to be 15,000, which is 150 times higher than the value for a commercial silver nanoparticle paper-based substrate. This study demonstrates the utility of atmospheric pulsed laser deposition for the fabrication of noble metal nanoparticle films, and offers new approaches to tailoring the particle morphology for high SERS performance.

Atmospheric-PLD as a New Trend for Nanofabrication in Nanotechnology

Research & Development in Material Science, 2018

Nanotechnology has emerged as a multidisciplinary technology, feeding all sectors of nanosciences... more Nanotechnology has emerged as a multidisciplinary technology, feeding all sectors of nanosciences and nanoengineering. Today, smart materials with entirely altered chemical and physical properties and devising new technological methods to produce such materials is on priority of nanotechnology. While working in this direction, recently a new method of atmospheric PLD (APLD) was explored and developed. This method shifts the fabrication of plasmonic nanomaterials into a completely simple, feasible, environmentally friendly and industrial oriented technique. In this newly introduced method, ablation plume produced by a pulse laser of enough fluence at atmospheric gas pressure, is captured by the gas to form a nanoparticle (NP) aerosol by collisional condensation. The NP aerosol is transported by various gas flow or flowing plasma approaches to produce NP film which are directly used as SERS substrates for chemical detection purpose.

What’s new in laser based nanofabrication for the fast uptake in industrial application

Materials Science: Materials Review, 2019

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

Electron Affinity and Bandgap Optimization of Zinc Oxide for Improved Performance of ZnO/Si Heterojunction Solar Cell Using PC1D Simulations

Electronics, 2019

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.

Synthesis of Pyramid-Shaped NiO Nanostructures using Low-Temperature Composite- Hydroxide- Mediated Approach

Journal of Material Science & Engineering, 2016

Composite-hydroxide-mediated (CHM) approach was used to synthesize NiO nanocrystals. The proposed... more Composite-hydroxide-mediated (CHM) approach was used to synthesize NiO nanocrystals. The proposed method makes use of molten composite hydroxides; providing reaction media and lower the process temperature. Processing temperature and reaction time are the two potential parameters to control the growth of a nanomaterial. The method was used at temperatures in the range of 180-250°C and formation of the nanomaterial was monitored using XRD, SEM, EDX, FTIR, and UV-visible spectroscopy. The produced nanomaterial was purely polycrystalline with an average crystallite size in the range of 23.71-36.92 nm. Method suggested formation of pyramid shaped NiO nanocrystals in the temperature range 220-250°C. Evidence on the elemental composition, purity, and chemical bonding were obtained from EDX and FTIR analysis respectively. Estimation on direct bandgap was made from the optical analysis and found to be in the range 4.0-4.8 eV. The method is attractive and seems a cost effective route for the growth of transition metal oxides for research purpose. For further efficacy, the approach can be examined for other technologically significant nanostructures.

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

Advanced Materials Letters, 2015

We report synthesis of the functional ZnO nanostructures (nanowires, nanorods) by a cost effectiv... more 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 ultraviolet (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 E 2 (high) phonon mode. The applied approach is believed to be an efficient, and a direct route for the synthesis of a wide range simple and complex oxide nanostructures for novel electro-optical nanodevices.

Synthesis And Doping Feasibility Of Composite-hydroxide-mediated Approach For The Cu1-xZnxO Nanomaterials

Advanced Materials Letters, 2016

In this article, we report feasibility of composite hydroxide-mediated (CHM) approach for the syn... more In this article, we report feasibility of composite hydroxide-mediated (CHM) approach for the synthesis and doping of Cu1-xZnxO (x=0%, 3%, 6% and 9%) nanomaterial. The proposed method offers a low cost, low temperature and environmentally friendly approach to preparing doped nanomaterials in a feasible and cost-effective route. Further, we investigate the effect of incorporated Zn +2 on the properties of produced Cu (II) O nanostructures. The X-ray diffraction analysis confirms formation of the single-phase monoclinic Cu (II) O and incorporation of Zn at the Cu-lattice sites. The crystalline structure is improved and the average grain size has increased from 85.32 nm to 124.86 nm. FTIR spectroscopy shows characteristic vibrational peaks of the Cu (II)-O bonding which confirms formation of the Cu (II) O. SEM micrographs reveal interesting flower like dense features with morphological peculiarities and seems to strongly depend on the content of the incorporated Zn +2. The UV-visible spectra are measured to study the direct bandgap of the prepared nanomaterial. The direct bandgap found to be in the range of 3.73-3.89 eV. The method seems experimentally friendly and provides a feasible and a high productive fast synthesis route for the doped oxide nanomaterials in a single step with tunable properties for the research purposes. However, the method still requires further investigation to finely control doping for the desired properties of a nanomaterial and to give a potential avenue for further practical scale-up of the production process and applications of novel devices based on doped nanostructures.

Annealing-induced effects on structural and optical properties of Cd1−xZnxS thin films for optoelectronic applications

Materials Science-Poland, 2015

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...

Tunability of physical properties of (Cd:Zn)S thin film by Close Space Sublimation Process (CSSP)

Progress in Natural Science: Materials International, 2012

Atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver with flowing gas and flowing atmospheric plasma

Applied Physics A, 2018

Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are ... more Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are described. In both methods the ablation plume, produced by a 248 nm, 20 ns excimer laser in gas, is strongly confined near the target and forms a nanoparticle aerosol. For both the flowing gas, and the atmospheric plasma from a dielectric barrier discharge plasma source, the aerosol is entrained in the flow and carried to a substrate for deposition. The nanoparticle films produced by both methods were examined by electron microscopy and optical absorption spectroscopy. With plasma assistance, the deposition rate was significantly enhanced and the film morphology altered. With argon gas, isolated nanoparticles of 20 nm size were obtained, whereas in argon plasma, the nanoparticles are aggregated in clusters of 90 nm size. Helium gas also leads to the deposition of isolated nanoparticles, but with helium plasma, two populations of nanoparticles are observed: one of rounded particles with a mean size of 26 nm and the other of faceted particles with a mean size 165 nm.

Author Correction: Processing laser ablated plasmonic nanoparticle aerosols with nonthermal dielectric barrier discharge jets of argon and helium and plasma induced effects

Scientific Reports

Processing laser ablated plasmonic nanoparticle aerosols with nonthermal dielectric barrier discharge jets of argon and helium and plasma induced effects

Scientific Reports

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 ...

Synthesis and optical study of heat-treated ZnO nanopowder for optoelectronic applications

Bulletin of Materials Science, 2015

Smart integration of cold plasma stream and surface discharge with ns laser ablation for composite nanomaterial

Discover Nano, May 27, 2024

Applications of DBD plasma jets in the advanced nanomaterials and COVID-19 pandemic

Elsevier eBooks, 2022

Chemical Analysis of Thermoluminescent Colorless Topaz Crystal Using Laser-Induced Breakdown Spectroscopy

Minerals, 2021

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...

In vitro bactericidal, antidiabetic, cytotoxic, anticoagulant, and hemolytic effect of green-synthesized silver nanoparticles using Allium sativum clove extract incubated at various temperatures

Green Processing and Synthesis, 2020

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,...

Compositional Analysis of Chalcopyrite Using Calibration-Free Laser-Induced Breakdown Spectroscopy

Applied Sciences, 2020

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...

Quantification of elemental composition of Granite Gneiss collected from Neelum Valley using calibration free laser-induced breakdown and energy-dispersive X-ray spectroscopy

Journal of Radiation Research and Applied Sciences, 2020

Calibrationfree laser-induced breakdown spectroscopy (CF-LIBS) has been employed for elemental an... more Calibrationfree laser-induced breakdown spectroscopy (CF-LIBS) has been employed for elemental analysis of Granite Gneiss, rock sample, collected from Neelum Valley of Azad Jammu & Kashmir, Pakistan. The sample was irradiated with focused laser beam from Q-switched Neodymium Yttrium Aluminum Garnet laser, having 532 nm wavelength and pulse width of 5 ns, and the emission spectrum was recorded with a spectrometer. Overall, ten elements viz. Si, Al, K, Fe, Sr, Ca, Mg, Na, Li, and H were identified by inspecting the characteristic emission lines. Out of ten detected elements, seven elements fulfilling the criteria of calibration-free technique, namely: Si, Al, K, Fe, Sr, Ca, and Mg, were quantified. Sample was also analyzed by employing energydispersive X-ray spectroscopy (EDX) and the results confirmed the presence of all those elements in the sample that were detected by LIBS, except Li and H. For the most abundant element Si in the Granite Gneiss sample, a significant agreement of two techniques for the quantitative results is obtained. Both the techniques have confirmed that Granite Gneiss consists mainly of Si with abundance of 72.75% and 71.30% by weight as measured by CF-LIBS and EDX, respectively. Findings of study show that for the elements with minor concentrations, quantitative results as measured with both techniques were not in close agreement.

Atmospheric DBD Plasma Source in Play for SERS Active Substrates

Biomedical Journal of Scientific & Technical Research, 2019

High resolution SERS spectra has made possible to do multicomponent analysis simultaneously. This... more High resolution SERS spectra has made possible to do multicomponent analysis simultaneously. This has driven the production demand of SERS substrates by technically feasible methods for further uptake on industrial scale. Here, a new idea of combining an atmospheric DBD plasma with ablation process at atmospheric gas pressure, is floated and described. The out flow from a DBD source, developed in flowing argon or helium is used to drive the plasmonic NP aerosol, produced from ablation of silver or gold target. The NP aerosols carried with the plasma jet, directly land on the solid surface and act as "hot spots" and makes a SERS active substrate to directly use for detection purpose. It is expected that the interaction of the plasma jet with the substrate would lead to formation of different morphologies and peculiar structures, and magnitude of SERS enhancement. The proposed approach seems handy to make flexible SERS substrate such as paper and to use directly for a wide range chemical and biological detection.

Various pulsed laser deposition methods for preparation of silver-sensitised glass and paper substrates for surface-enhanced Raman spectroscopy

Applied Physics A, 2019

Silver nanoparticle films on glass and paper were prepared using vacuum pulsed laser deposition, ... more Silver nanoparticle films on glass and paper were prepared using vacuum pulsed laser deposition, and various methods of atmospheric pulsed laser deposition, where ablated material forms a nanoparticle aerosol near the target and is delivered in a gas flow to the substrate. The performance of the films for surface-enhanced Raman spectroscopy (SERS) was investigated using a 10-4 M aqueous solution of rhodamine 6G organic dye. The SERS sensitivity was quantified in terms of the apparent enhancement factor and the signal-to-noise ratio. For the films made by supersonic atmospheric pulsed laser deposition, the apparent enhancement factor was found to be 15,000, which is 150 times higher than the value for a commercial silver nanoparticle paper-based substrate. This study demonstrates the utility of atmospheric pulsed laser deposition for the fabrication of noble metal nanoparticle films, and offers new approaches to tailoring the particle morphology for high SERS performance.

Atmospheric-PLD as a New Trend for Nanofabrication in Nanotechnology

Research & Development in Material Science, 2018

Nanotechnology has emerged as a multidisciplinary technology, feeding all sectors of nanosciences... more Nanotechnology has emerged as a multidisciplinary technology, feeding all sectors of nanosciences and nanoengineering. Today, smart materials with entirely altered chemical and physical properties and devising new technological methods to produce such materials is on priority of nanotechnology. While working in this direction, recently a new method of atmospheric PLD (APLD) was explored and developed. This method shifts the fabrication of plasmonic nanomaterials into a completely simple, feasible, environmentally friendly and industrial oriented technique. In this newly introduced method, ablation plume produced by a pulse laser of enough fluence at atmospheric gas pressure, is captured by the gas to form a nanoparticle (NP) aerosol by collisional condensation. The NP aerosol is transported by various gas flow or flowing plasma approaches to produce NP film which are directly used as SERS substrates for chemical detection purpose.

What’s new in laser based nanofabrication for the fast uptake in industrial application

Materials Science: Materials Review, 2019

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

Electron Affinity and Bandgap Optimization of Zinc Oxide for Improved Performance of ZnO/Si Heterojunction Solar Cell Using PC1D Simulations

Electronics, 2019

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.

Synthesis of Pyramid-Shaped NiO Nanostructures using Low-Temperature Composite- Hydroxide- Mediated Approach

Journal of Material Science & Engineering, 2016

Composite-hydroxide-mediated (CHM) approach was used to synthesize NiO nanocrystals. The proposed... more Composite-hydroxide-mediated (CHM) approach was used to synthesize NiO nanocrystals. The proposed method makes use of molten composite hydroxides; providing reaction media and lower the process temperature. Processing temperature and reaction time are the two potential parameters to control the growth of a nanomaterial. The method was used at temperatures in the range of 180-250°C and formation of the nanomaterial was monitored using XRD, SEM, EDX, FTIR, and UV-visible spectroscopy. The produced nanomaterial was purely polycrystalline with an average crystallite size in the range of 23.71-36.92 nm. Method suggested formation of pyramid shaped NiO nanocrystals in the temperature range 220-250°C. Evidence on the elemental composition, purity, and chemical bonding were obtained from EDX and FTIR analysis respectively. Estimation on direct bandgap was made from the optical analysis and found to be in the range 4.0-4.8 eV. The method is attractive and seems a cost effective route for the growth of transition metal oxides for research purpose. For further efficacy, the approach can be examined for other technologically significant nanostructures.

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

Advanced Materials Letters, 2015

We report synthesis of the functional ZnO nanostructures (nanowires, nanorods) by a cost effectiv... more 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 ultraviolet (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 E 2 (high) phonon mode. The applied approach is believed to be an efficient, and a direct route for the synthesis of a wide range simple and complex oxide nanostructures for novel electro-optical nanodevices.

Synthesis And Doping Feasibility Of Composite-hydroxide-mediated Approach For The Cu1-xZnxO Nanomaterials

Advanced Materials Letters, 2016

In this article, we report feasibility of composite hydroxide-mediated (CHM) approach for the syn... more In this article, we report feasibility of composite hydroxide-mediated (CHM) approach for the synthesis and doping of Cu1-xZnxO (x=0%, 3%, 6% and 9%) nanomaterial. The proposed method offers a low cost, low temperature and environmentally friendly approach to preparing doped nanomaterials in a feasible and cost-effective route. Further, we investigate the effect of incorporated Zn +2 on the properties of produced Cu (II) O nanostructures. The X-ray diffraction analysis confirms formation of the single-phase monoclinic Cu (II) O and incorporation of Zn at the Cu-lattice sites. The crystalline structure is improved and the average grain size has increased from 85.32 nm to 124.86 nm. FTIR spectroscopy shows characteristic vibrational peaks of the Cu (II)-O bonding which confirms formation of the Cu (II) O. SEM micrographs reveal interesting flower like dense features with morphological peculiarities and seems to strongly depend on the content of the incorporated Zn +2. The UV-visible spectra are measured to study the direct bandgap of the prepared nanomaterial. The direct bandgap found to be in the range of 3.73-3.89 eV. The method seems experimentally friendly and provides a feasible and a high productive fast synthesis route for the doped oxide nanomaterials in a single step with tunable properties for the research purposes. However, the method still requires further investigation to finely control doping for the desired properties of a nanomaterial and to give a potential avenue for further practical scale-up of the production process and applications of novel devices based on doped nanostructures.

Annealing-induced effects on structural and optical properties of Cd1−xZnxS thin films for optoelectronic applications

Materials Science-Poland, 2015

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...

Tunability of physical properties of (Cd:Zn)S thin film by Close Space Sublimation Process (CSSP)

Progress in Natural Science: Materials International, 2012

Atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver with flowing gas and flowing atmospheric plasma

Applied Physics A, 2018

Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are ... more Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are described. In both methods the ablation plume, produced by a 248 nm, 20 ns excimer laser in gas, is strongly confined near the target and forms a nanoparticle aerosol. For both the flowing gas, and the atmospheric plasma from a dielectric barrier discharge plasma source, the aerosol is entrained in the flow and carried to a substrate for deposition. The nanoparticle films produced by both methods were examined by electron microscopy and optical absorption spectroscopy. With plasma assistance, the deposition rate was significantly enhanced and the film morphology altered. With argon gas, isolated nanoparticles of 20 nm size were obtained, whereas in argon plasma, the nanoparticles are aggregated in clusters of 90 nm size. Helium gas also leads to the deposition of isolated nanoparticles, but with helium plasma, two populations of nanoparticles are observed: one of rounded particles with a mean size of 26 nm and the other of faceted particles with a mean size 165 nm.

Author Correction: Processing laser ablated plasmonic nanoparticle aerosols with nonthermal dielectric barrier discharge jets of argon and helium and plasma induced effects

Scientific Reports

Processing laser ablated plasmonic nanoparticle aerosols with nonthermal dielectric barrier discharge jets of argon and helium and plasma induced effects

Scientific Reports

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 ...