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1.	ul Hassan Alvi, Naveed, et al. (author) InN/InGaN quantum dot photoelectrode: Efficient hydrogen generation by water splitting at zero voltage 2015 In: NANO ENERGY. - : Elsevier. - 2211-2855. ; 13, s. 291-297 Journal article (peer-reviewed)abstract Light to hydrogen conversion via water splitting is of immense interest as a clean, storable, and InN; renewable energy source (Tachibana et al., 2012 [1]; Maeda and Domen, 2010 [2]; van de Krol et al., Quantum dots; 2008 [3]; van Dorp et al., 2009 [4]; Kudo and Miseki, 2009 [5]) but efficient materials need to be found. Photoelect rode; To solve, InGaN has properties ideally suited and we demonstrate here that epitaxial InN quantum dots Water splitting; Hydrogen generation (QDs) more than double the photoelectrochemical (PEC) water splitting efficiency of an In0.54Ga046N photoelectrode. The InN/In0.54Ga0.46N-QDs-photoelectrode reveals a maximum incident-photon-tocurrent-conversion efficiency (IPCE) of up to 56% at a wavelength of 600 nm with hydrogen generation rate of 133 mot h(-1) cm(-2) at zero voltage under illumination of a 1000W Xenon arc lamp. The bare In0.51Ga0.16N-layer-photoelectrode reveals a much lower IPCE of 24% with hydrogen generation rate of 59 pmol h(-1) cm(-2). (C) 2015 Elsevier Ltd. All rights reserved.
2.	Ul Hassan Alvi, Naveed, et al. (author) Influence of different growth environments on the luminescence properties of ZnO nanorods grown by the vapor-liquid-solid (VLS) method 2013 In: Materials letters (General ed.). - : Elsevier. - 0167-577X .- 1873-4979. ; 106, s. 158-163 Journal article (peer-reviewed)abstract ZnO nanorods (NRs) are grown in different atmospheres (argon, air, oxygen and nitrogen) by using the vapor-liquid-solid (VLS) method. The influence of different growth atmospheres on the luminescence properties has been investigated by using the photoluminescence (PL), cathodoluminescence (CL) and electroluminescence (EL) spectra measurements at room temperature. The PL spectra investigations reveal that the air, the oxygen and the nitrogen growth atmospheres have strongly affected the oxygen interstitial (O-i) and oxygen vacancy (V-o) related deep level emission (DLE) bands in ZnO and this fact is also found consistent with the cathodoluminescence (CL) and electroluminescence (EL) spectra investigations. The color rendering investigations reveal that the growth atmospheres have also influenced the color quality of the emitted light. These results indicate that the defects related emissions from the band gap of ZnO NRs can be tuned by using different growth atmospheres. These results can be useful for the development of white light emitting diodes (WLEDs).
3.	Alvi, Naveed ul Hassan, et al. (author) The effect of the post-growth annealin g on the color rendering properties of n-Zn Onanorods /p-GaN light emitting diodes 2011 In: Lighting Research and Technology. - : Sage. - 1477-1535 .- 1477-0938. ; 43:3, s. 331-336 Journal article (peer-reviewed)abstract The effect of post-growth annealing on the colour properties of the light emitted by n-ZnO nanorods/p-GaN white LEDs has been investigated. The as-grown ZnO nanorods were annealed in nitrogen, oxygen, argon and air atmospheres at 6008C for 30 minutes. The colour rendering indices and correlated colour temperatures were calculated from the spectra emitted by the LEDs. It was observed that the ambient atmosphere used for annealing is very effective for altering the colour properties of the fabricated LEDs. The LEDs annealed in nitrogen have excellent colour rendering properties with a colour rendering index and a correlated colour temperature of 97 and 2363 K, respectively, in the forward bias and 98 and 3157K in the reverse bias.
4.	Faraz, Sadia, et al. (author) Effect of annealing atmosphere on the diode behaviourof zno/si heterojunction 2021 In: Elektronika ir Elektrotechnika. - : Kauno Technologijos Universitetas. - 1392-1215 .- 2029-5731. ; 27:4, s. 49-54 Journal article (peer-reviewed)abstract The effect of thermal annealing atmosphere on the electrical characteristics of Zinc oxide (ZnO) nanorods/p-Silicon (Si) diodes is investigated. ZnO nanorods are grown by low-temperature aqueous solution growth method and annealed in Nitrogen and Oxygen atmosphere. As-grown and annealed nanorods are studied by scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electrical characteristics of ZnO/Si heterojunction diodes are studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. Improvements in rectifying behaviour, ideality factor, carrier concentration, and series resistance are observed after annealing. The ideality factor of 4.4 for as-grown improved to 3.8 and for Nitrogen and Oxygen annealed improved to 3.5 nanorods diodes. The series resistances decreased from 1.6 to 1.8 times after annealing. An overall improved behaviour is observed for oxygen annealed heterojunction diodes. The study suggests that by controlling the ZnO nanorods annealing temperatures and atmospheres the electronic and optoelectronic properties of ZnO devices can be improved.
5.	Faraz, S. M., et al. (author) Effect of annealing temperature on the interface state density of n-ZnO nanorod/p-Si heterojunction diodes 2021 In: Open Physics. - : De Gruyter Open Ltd. - 2391-5471. ; 19:1, s. 467-476 Journal article (peer-reviewed)abstract The effect of post-growth annealing treatment of zinc oxide (ZnO) nanorods on the electrical properties of their heterojunction diodes (HJDs) is investigated. ZnO nanorods are synthesized by the low-temperature aqueous solution growth technique and annealed at temperatures of 400 and 600°C. The as-grown and annealed nanorods are studied by scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electrical characterization of the ZnO/Si heterojunction diode is done by current–voltage (I–V) and capacitance–voltage (C–V) measurements at room temperature. The barrier height (ϕB), ideality factor (n), doping concentration and density of interface states (NSS) are extracted. All HJDs exhibited a nonlinear behavior with rectification factors of 23, 1,596 and 309 at ±5 V for the as-grown, 400 and 600°C-annealed nanorod HJDs, respectively. Barrier heights of 0.81 and 0.63 V are obtained for HJDs of 400 and 600°C-annealed nanorods, respectively. The energy distribution of the interface state density has been investigated and found to be in the range 0.70 × 1010 to 1.05 × 1012 eV/cm2 below the conduction band from EC = 0.03 to EC = 0.58 eV. The highest density of interface states is observed in HJDs of 600°C-annealed nanorods. Overall improved behavior is observed for the heterojunctions diodes of 400°C-annealed ZnO nanorods. © 2021 Sadia Muniza Faraz et al.
6.	Muniza Faraz, Sadia, et al. (author) Post fabrication annealing effects on electrical and optical characteristics of n-ZnO nanorods/p-Si heterojunction diodes Other publication (other academic/artistic)abstract Annealing effects on optical and electrical properties of n-ZnO/p-Si heterojunction diodes are studied. ZnO nanorods are grown on p-Si substrate by aquous chemical growth technique. As grown samples were annealed at 400 and 600 oC in air, oxygen and nitrogen ambient. Structural, optical and electrical characteristics are studied by Scanning Electron Microscopy (SEM), Photoluminescence (PL), Current–Voltage (I-V) and Capacitance-Voltage (CV) measurements. Well aligned hexagonal–shaped vertical nanorods are revealed in SEM. PL spectra indicated higher ultraviolet to visible emission ratio with a strong peak ofnear band edge emission (NBE) and weak broad deep-level emissions (DLE). For device fabrication Al/Pt non-alloyed ohmic contacts have been evaporated. I-V characteristics indicate that annealing in air and oxygen resulted in better rectifying behavior as well as decrease in reverse leakage current. An improvement in PL intensity has been shown by the samples annealed at 400 oC.
7.	Ul Hasan, Kamran, et al. (author) Single nanowire-based UV photodetectors for fast switching 2011 In: Nanoscale Research Letters. - : Springer Science Business Media. - 1931-7573 .- 1556-276X. ; 6:348 Journal article (peer-reviewed)abstract Relatively long (30 mu m) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.
8.	Ul Hassan Alvi, Naveed, et al. (author) The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes 2011 In: NANOSCALE RESEARCH LETTERS. - : Springer Science Business Media. - 1931-7573. ; 6:1, s. 130- Journal article (peer-reviewed)abstract In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600 degrees C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (O-i) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (V-o) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.
9.	Alvi, Naveed ul Hassan, et al. (author) Fabrication and characterization of high-brightness light emitting diodes based on n-ZnO nanorods grown by a low-temperature chemical method on p-4H-SiC and p-GaN 2010 In: Semiconductor Science and Technology. - : Iop Publishing Ltd. - 0268-1242 .- 1361-6641. ; 25:6, s. 065004- Journal article (peer-reviewed)abstract Light emitting diodes (LEDs) based on n-ZnO nanorods (NRs)/p-4H-SiC and n-ZnO (NRs)/p-GaN were fabricated and characterized. For the two LEDs the ZnO NRs were grown using a low temperature (andlt;100 degrees C) aqueous chemical growth (ACG) technique. Both LEDs showed very bright nearly white light electroluminescence (EL) emission. The observed luminescence was a result of the combination of three emission lines composed of violet-blue, green and orange-red peaks observed from the two LEDs. Room temperature photoluminescence (PL) was also measured and consistency with EL was observed. It was found that the green and violet-blue peaks are red-shifted while the orange peak is blue-shifted in the EL measurement. It was also found that due to the effect of the GaN substrate the violet-blue peak in the EL measurement is more red-shifted in n-ZnO (NRs)/p-GaN LEDs as compared to n-ZnO (NRs)/p-4H-SiC LEDs.
10.	Alvi, Naveed ul Hassan, et al. (author) Influence of helium-ion bombardment on the optical properties of ZnO nanorods/p-GaN light emitting diodes 2011 In: Nanoscale Research Letters. - : SpringerOpen. - 1931-7573 .- 1556-276X. ; 6:628 Journal article (peer-reviewed)abstract Light emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods grown by vapor-liquid-solid (VLS) catalytic growth method were irradiated with 2 MeV helium (He+) ions. The fabricated LEDs were irradiated with fluencies of ~ 2×1013 ions/cm2 and ~ 4×1013 ions/cm2. Scanning electron microscopy (SEM) images showed that the morphology of the irradiated samples is not changed. The as-grown and He+ irradiated LEDs showed rectifying behaviour with the same I-V characteristics. Photoluminescence (PL) measurements showed that there is a blue shift of approximately 0.0347 eV and 0.082 eV in the near band emission (free exciton) and green emission of the irradiated ZnO nanorods, respectively. It was also observed that the PL intensity of the near band emission was decreased after irradiation of the samples. The electroluminescence (EL) measurements of the fabricated LEDs showed that there is a blue shift of 0.125 eV in the broad green emission after irradiation and the EL intensity of violet emission approximately centred at 398 nm was nearly disappeared after irradiations. The color rendering properties shows a small decrease in the color rendering indices of 3% after 2 MeV He+ ions irradiation.
11.	Alvi, Naveed ul Hassan (author) Luminescence Properties of ZnO Nanostructures and Their Implementation as White Light Emitting Diodes (LEDs) 2011 Doctoral thesis (other academic/artistic)abstract In this thesis, luminescence properties of ZnO nanostructures (nanorods, nanotubes, nanowalls and nanoflowers) are investigated by different approaches for possible future application of these nanostructures as white light emitting diodes. ZnO nanostructures were grown by different growth techniques on different p-type substrates. Still it is a challenge for the researchers to produce a stable and reproducible high quality p-type ZnO and this seriously hinders the progress of ZnO homojunction LEDs. Therefore the excellent properties of ZnO can be utilized by constructing heterojunction with other p-type materials.The first part of the thesis includes paper I-IV. In this part, the luminescence properties of ZnO nanorods grown on different p-type substrates (GaN, 4H-SiC) and different ZnO nanostructures (nanorods, nanotubes, nanoflowers, and nanowalls) grown on the same substrate were investigated. The effect of the post-growth annealing of ZnO nanorods and nanotubes on the deep level emissions and color rendering properties were also investigated.In paper I, ZnO nanorods were grown on p-type GaN and 4H-SiC substrates by low temperature aqueous chemical growth (ACG) method. The luminescence properties of the fabricated LEDs were investigated at room temperature by electroluminescence (EL) and photoluminescence (PL) measurements and consistency was found between both the measurements. The LEDs showed very bright emission that was a combination of three emission peaks in the violet-blue, green and orange-red regions in the visible spectrum.In paper II, different ZnO nanostructures (nanorods, nanotubes, nanoflowers, and nanowalls) were grown on p-GaN and the luminescence properties of these nanostructures based LEDs were comparatively investigated by EL and PL measurements. The nanowalls structures were found to be emitting the highest emission in the visible region, while the nanorods have the highest emissions in the UV region due to its good crystal quality. It was also estimated that the ZnO nanowalls structures have strong white light with the highest color rendering index (CRI) of 95 with correlated color temperature (CCT) of 6518 K.In paper III, we have investigated the origin of the red emissions in ZnO by using post-growth annealing. The ZnO nanotubes were achieved on p-GaN and then annealed in different ambients (argon, air, oxygen and nitrogen) at 600 oC for 30 min. By comparative investigations of EL spectra of the LEDs it was found that more than one deep level defects are involved in the red emission from ZnO nanotubes/p-GaN LEDs. It was concluded that the red emission in ZnO can be attributed to oxygen interstitials (Oi) and oxygen vacancies (Vo) in the range of 620 nm (1.99 eV) to 690 nm (1.79 eV) and 690 nm (1.79 eV) to 750 nm (1.65 eV), respectively.In paper IV, we have investigated the effect of post-growth annealing on the color rendering properties of ZnO nanorods based LEDs. ZnO nanorods were grown on p-GaN by using ACG method. The as grown nanorods were annealed in nitrogen, oxygen, argon, and air ambients at 600 oC for 30 min. The color rendering indices (CRIs) and correlated color temperatures (CCTs) were estimated from the spectra emitted by the LEDs. It was found that the annealing ambients especially air, oxygen, and nitrogen were found to be very effective. The LEDs based on nanorods annealed in nitrogen ambient, have excellent color rendering properties with CRIs and CCTs of 97 and 2363 K in the forward bias and 98 and 3157 K in the reverse bias.In the 2nd part of the thesis, the junction temperature of n-ZnO nanorods based LEDs at the built-in potential was modeled and experiments were performed to validate the model. The LEDs were fabricated by ZnO nanorods grown on different p-type substrates (4H-SiC, GaN, and Si) by the ACG method. The model and experimental values of the temperature coefficient of the forward voltage near the built-in potential (~Vo) were compared. It was found that the series resistance has the main contribution in the junction temperature of the fabricated devices.In the 3rd part of the thesis, the influence of helium (He+) ion irradiation bombardment on luminescence properties of ZnO nanorods based LEDs were investigated. ZnO nanorods were grown by the vapor-liquid-solid (VLS) growth method. The fabricated LEDs were irradiated by using 2 MeV He+ ions with fluencies of ~ 2×1013 ions/cm2 and ~ 4×1013 ions/cm2. It was observed that the He+ ions irradiation affects the near band edge emissions as well as the deep level emissions in ZnO. A blue shift about 0.0347 eV and 0.082 eV was observed in the PL spectra in the near band emission and green emission, respectively. EL measurements also showed a blue shift of 0.125 eV in the broad green emission after irradiation. He+ ion irradiation affects the color rendering properties and decreases the color rendering indices from 92 to 89.
12.	Alvi, Naveed, et al. (author) Unassisted water splitting with 9.3% efficiency by a single quantum nanostructure photoelectrode 2019 In: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 44:36, s. 19650-19657 Journal article (peer-reviewed)abstract To split water and produce hydrogen by white light is an excellent solution for the storage and supply of clean and sustainable energy. Efficiency and stability are the key challenges for a successful exploitation. InGaN, evaluated against other semiconductors, metal oxides, carbon based - and organic materials has most suited intrinsic materials properties. Based on this optimum materials choice we report photoelectrochemical (PEC) hydrogen generation under white light illumination by an InGaN-based quantum nanostructure photoelectrode. No degradation occurs for operation over 10 h. Our novel concept, combining quantum nanostructure physics with electrochemistry and catalysis leads to almost 10% efficiency at zero external voltage. The efficiency rises above 25% at 0.2 V. This is unmatched for a single photoelectrode, representing the most advanced technology of low complexity. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
13.	Edberg, Jesper, 1988-, et al. (author) A Forest-Based Triboelectric Energy Harvester 2022 In: Global Challenges. - : John Wiley and Sons Inc. - 2056-6646. ; 6:10 Journal article (peer-reviewed)abstract Triboelectric nanogenerators (TENGs) are a new class of energy harvesting devices that have the potential to become a dominating technology for producing renewable energy. The versatility of their designs allows TENGs to harvest mechanical energy from sources like wind and water. Currently used renewable energy technologies have a restricted number of materials from which they can be constructed, such as metals, plastics, semiconductors, and rare-earth metals. These materials are all non-renewable in themselves as they require mining/drilling and are difficult to recycle at end of life. TENGs on the other hand can be built from a large repertoire of materials, including materials from bio-based sources. Here, a TENG constructed fully from wood-derived materials like lignin, cellulose, paper, and cardboard, thus making it 100% green, recyclable, and even biodegradable, is demonstrated. The device can produce a maximum voltage, current, and power of 232 V, 17 mA m–2, and 1.6 W m–2, respectively, which is enough to power electronic systems and charge 6.5 µF capacitors. Finally, the device is used in a smart package application as a self-powered impact sensor. The work shows the feasibility of producing renewable energy technologies that are sustainable both with respect to their energy sources and their material composition. © 2022 The Authors.
14.	Fulati, Alimujiang, 1981-, et al. (author) An intracellular glucose biosensor based on nanoflake ZnO 2010 In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 150:2, s. 673-680 Journal article (other academic/artistic)abstract In this study, an improved potentiometric intracellular glucose biosensor was fabricated with immobilization of glucose oxidase on a ZnO nanoporous material. The ZnO nanoporous material with a wall thickness around 200 nm was grown on the tip of a borosilicate glass capillary and used as a selective intracellular glucose sensor for the measurement of glucose concentrations in human adipocytes and frog oocytes. The results showed a fast response within 4 s and a linear glucosedependent electrochemical response over a wide range of glucose concentration (500 nM-10 mM). The measurements of intracellular glucose concentrations with our biosensor were consistent with the values of intracellular glucose concentrations reported in the literature. The sensor also demonstrated its capability by detecting an increase in the intracellular glucose concentration induced by insulin. We found that the ZnO nanoporous material provides sensitivity as high as 1.8 times higher than that obtained using ZnO nanorods under the same conditions. Moreover, the fabrication method in our experiment is simple and the excellent performance of the developed nanosensor in sensitivity, stability, selectivity, reproducibility and anti-interference was achieved. All these advantageous features of this intracellular glucose biosensor based on functionalised ZnO nanoporous material compared to ZnO nanorods demonstrate a promising way of enhancing glucose biosensor performance to measure reliable intracellular glucose concentrations within single living cells.
15.	Han, Shaobo, et al. (author) A Multiparameter Pressure–Temperature–Humidity Sensor Based on Mixed Ionic–Electronic Cellulose Aerogels 2019 In: Advanced Science. - : Wiley. - 2198-3844. Journal article (peer-reviewed)abstract Pressure (P), temperature (T), and humidity (H) are physical key parameters of great relevance for various applications such as in distributed diagnostics, robotics, electronic skins, functional clothing, and many other Internet-of-Things (IoT) solutions. Previous studies on monitoring and recording these three parameters have focused on the integration of three individual single-parameter sensors into an electronic circuit, also comprising dedicated sense amplifiers, signal processing, and communication interfaces. To limit complexity in, e.g., multifunctional IoT systems, and thus reducing the manufacturing costs of such sensing/communication outposts, it is desirable to achieve one single-sensor device that simultaneously or consecutively measures Pâ€“Tâ€“H without cross-talks in the sensing functionality. Herein, a novel organic mixed ionâ€“electron conducting aerogel is reported, which can sense Pâ€“Tâ€“H with minimal cross-talk between the measured parameters. The exclusive read-out of the three individual parameters is performed electronically in one single device configuration and is enabled by the use of a novel strategy that combines electronic and ionic Seebeck effect along with mixed ionâ€“electron conduction in an elastic aerogel. The findings promise for multipurpose IoT technology with reduced complexity and production costs, features that are highly anticipated in distributed diagnostics, monitoring, safety, and security applications. © 2019 The Authors.
16.	Majee, Subimal, et al. (author) Low temperature chemical sintering of inkjet-printed Zn nanoparticles for highly conductive flexible electronic components 2021 In: npj Flexible Electronics. - : Nature Research. - 2397-4621. ; 5:1 Journal article (peer-reviewed)abstract This study illustrates an innovative way to fabricate inkjet-printed tracks by sequential printing of Zn nanoparticle ink and curing ink for low temperature in situ chemical sintering. Employing chemical curing in place of standard sintering methods leads to the advantages of using flexible substrates that may not withstand the high thermal budgets of the standard methods. A general formulation engineering method is adopted to produce highly concentrated Zn ink which is cured by inkjet printing an over-layer of aqueous acetic acid which is the curing agent. The experimental results reveal that a narrow window of acid concentration of curing ink plays a crucial role in determining the electrical properties of the printed Zn nanoparticles. Highly conductive (~105 S m−1) and mechanically flexible printed Zn features are achieved. In addition, from systematic material characterization, we obtain an understanding of the curing mechanism. Finally, a touch sensor circuit is demonstrated involving all-Zn printed conductive tracks. © 2021, The Author(s).
17.	Shafa, Muhammad, et al. (author) Flexible infrared photodetector based on indium antimonide nanowire arrays 2021 In: Nanotechnology. - : NLM (Medline). - 0957-4484 .- 1361-6528. ; 32:27 Journal article (peer-reviewed)abstract Narrow bandgap semiconductors like indium antimonide (InSb) are very suitable for high-performance room temperature infrared photodetectors, but the fragile nature of the wafer materials hinders their application as flexible/wearable devices. Here, we present a method to fabricate a photodetector device of assembled crystalline InSb nanowire (NW) arrays on a flexible substrate that balances high performance and flexibility, facilitating its application in wearable devices. The InSb NWs were synthesized by means of a vapor-liquid-solid technique, with gold nanoclusters as seeding particles. The morphological and crystal properties were investigated using scanning electron microscopy, x-ray diffraction and high-resolution transmission electron microscopy, which revealed the unique spike shape and high crystallinity with (111) and (220) planes of InSb NWs. The flexible infrared photodetector devices were fabricated by transferring the NWs onto transparent and stretchable polydimethylsiloxane substrate with pre-deposited gold electrodes. Current versus time measurement of the photodetector devices under light showed photoresponsivity and sensitivity to mid-infrared at bias as low as 0.1 V while attached to curved surfaces (suitable for skin implants). A high-performance NW device yielded efficient rise and decay times down to 1 s and short time lag for infrared detection. Based on dark current, calculated specific detectivity of the flexible photodetector was 1.4 × 1012Jones. The performance and durability render such devices promising for use as wearable infrared photodetectors.
18.	ul Hassan Alvi, Naveed, et al. (author) An InN/InGaN Quantum Dot Electrochemical Biosensor for Clinical Diagnosis 2013 In: Sensors. - : MDPI. - 1424-8220. ; 13:10, s. 13917-13927 Journal article (peer-reviewed)abstract Low-dimensional InN/InGaN quantum dots (QDs) are demonstrated for realizing highly sensitive and efficient potentiometric biosensors owing to their unique electronic properties. The InN QDs are biochemically functionalized. The fabricated biosensor exhibits high sensitivity of 97 mV/decade with fast output response within two seconds for the detection of cholesterol in the logarithmic concentration range of 1 x 10(-6) M to 1 x 10(-3) M. The selectivity and reusability of the biosensor are excellent and it shows negligible response to common interferents such as uric acid and ascorbic acid. We also compare the biosensing properties of the InN QDs with those of an InN thin film having the same surface properties, i.e., high density of surface donor states, but different morphology and electronic properties. The sensitivity of the InN QDs-based biosensor is twice that of the InN thin film-based biosensor, the EMF is three times larger, and the response time is five times shorter. A bare InGaN layer does not produce a stable response. Hence, the superior biosensing properties of the InN QDs are governed by their unique surface properties together with the zero-dimensional electronic properties. Altogether, the InN QDs-based biosensor reveals great potential for clinical diagnosis applications.
19.	Ul Hassan Alvi, Naveed, et al. (author) Fabrication and comparative optical characterization of n-ZnO nanostructures (nanowalls, nanorods, nanoflowers and nanotubes)/p-GaN white-light-emitting diodes 2011 In: Scripta Materialia. - : Elsevier Science B.V., Amsterdam.. - 1359-6462 .- 1872-8456. ; 64:8, s. 697-700 Journal article (peer-reviewed)abstract White light-emitting diodes (LED) based on ZnO (nanowalls, nanorods, nanoflowers and nanotubes)/p-GaN were fabricated and their electrical, optical and electro-optical characteristics were comparatively characterized. All the LED showed rectifying behavior. The nanowalls and nanorods structures have the highest photoluminescence emission intensity in the visible and UV (at 3.29 eV) regions, respectively. The nanowalls have the highest color rendering index, with a value of 95, and the highest electroluminescence intensity with peaks approximately centered at 420, 450 nm and broad peak covering the visible region.
20.	ul Hassan Alvi, Naveed, et al. (author) Highly Sensitive and Fast Anion-Selective InN Quantum Dot Electrochemical Sensors 2013 In: APPLIED PHYSICS EXPRESS. - : Japan Society of Applied Physics. - 1882-0778. ; 6:11 Journal article (peer-reviewed)abstract Epitaxial InN quantum dots (QDs) are demonstrated as ion-selective electrode for potentiometric anion concentration measurements. The sensor reveals high sensitivity above 90 mV/decade for the detection of chlorine and hydroxyl ions in sodium chloride (NaCl), calcium chloride (CaCl2), and sodium hydroxide (NaOH) solutions. The response time is less than two seconds after which the signal is very stable and repeatable. The sensitivity for the InN QDs is about two times that for a reference InN thin film and the response time is about five times shorter. In pH buffer solutions the sensor reveals no clear response to cations. A model is presented for the high sensitivity, fast response, and ion selectivity based on the unique electronic properties of the InN surface together with the zero-dimensional nature of the QDs.
21.	Ul Hassan Alvi, Naveed, et al. (author) Junction temperature in n-ZnO nanorods/(p-4H-SiC, p-GaN, and p-Si) heterojunction light emitting diodes 2010 In: Solid-State Electronics. - : Elsevier Science B.V., Amsterdam.. - 0038-1101 .- 1879-2405. ; 54:5, s. 536-540 Journal article (peer-reviewed)abstract The junction temperature of n-ZnO nanorods/(p-4H-SiC, p-GaN, and p-Si) heterojunction light emitting diodes (LEDs) at built-in potential was modeled and experiments were performed at various temperatures (15-65 degrees C) to validate the model. As the LEDs operate near the built-in potential thats why it is interesting to investigate the temperature coefficient of forward voltage near the built-in potential (similar to V-o). The model and experimental values of the temperature coefficient of forward voltage near the built-in potential (similar to V-o) were compared. We measured the experimental temperature coefficient of the series resistance. By including the temperature coefficient of the series resistance in the model, the theoretical and experimental values become very close to each other. It was found that the series resistance has the main contribution in the junction temperature of our devices. We also measured the junction temperature above the built-in potential and found that the model deviates at higher forward voltage. From this observation we concluded that the model is applicable for low power devices, operated near the built-in potential.
22.	Ul Hassan Alvi, Naveed, et al. (author) Sustainable and Low-Cost Electrodes for Photocatalytic Fuel Cells 2024 In: Nanomaterials. - : Multidisciplinary Digital Publishing Institute (MDPI). - 2079-4991. ; 14:7 Journal article (peer-reviewed)abstract Water pollutants harm ecosystems and degrade water quality. At the same time, many pollutants carry potentially valuable chemical energy, measured by chemical oxygen demand (COD). This study highlights the potential for energy harvesting during remediation using photocatalytic fuel cells (PCFCs), stressing the importance of economically viable and sustainable materials. To achieve this, this research explores alternatives to platinum cathodes in photocathodes and aims to develop durable, cost-effective photoanode materials. Here, zinc oxide nanorods of high density are fabricated on carbon fiber surfaces using a low-temperature aqueous chemical growth method that is simple, cost-efficient, and readily scalable. Alternatives to the Pt cathodes frequently used in PCFC research are explored in comparison with screen-printed PEDOT:PSS cathodes. The fabricated ZnO/carbon anode (1.5 × 2 cm2) is used to remove the model pollutant used here and salicylic acid from water (30 mL, 70 μM) is placed under simulated sunlight (0.225 Sun). It was observed that salicylic acid was degraded by 23 ±0.46% at open voltage (OV) and 43.2 ± 0.86% at 1 V with Pt as the counter electrode, degradation was 18.5 ± 0.37% at open voltage (OV) and 44.1 ± 0.88% at 1 V, while PEDOT:PSS was used as the counter electrode over 120 min. This shows that the PEDOT:PSS exhibits an excellent performance with the full potential to provide low-environmental-impact electrodes for PCFCs.
23.	Ul Hassan Alvi, Naveed, et al. (author) The effect of the post-growth annealing on the electroluminescence properties of n-ZnO nanorods/p-GaN light emitting diodes 2010 In: Superlattices and Microstructures. - : Elsevier Science B.V., Amsterdam. - 0749-6036 .- 1096-3677. ; 47:6, s. 754-761 Journal article (peer-reviewed)abstract In this paper we investigated the effect of post-growth annealing treatment on the electroluminescence (EL) of n-ZnO nanorods/p-GaN light emitting diodes. The ZnO nanorods were grown by the low temperature (less than100 degrees C) aqueous chemical growth (ACC) technique. The as-grown ZnO nanorods were annealed in nitrogen, oxygen, argon, and air ambients at 600 degrees C for 30 min. The electroluminescence (EL) measurements showed that the deep level defects related emissions in ZnO were greatly affected by the annealing of the n-ZnO nanorods in different ambients. By comparing the EL spectra of ZnO nanorods annealed in different ambients it was found that nitrogen annealing ambient is very effective in shifting the emission peak from the green region to the red region. It was also concluded that the red emission in ZnO was attributed to oxygen vacancies WO. The effect of the annealing ambient and the temperature dependence electroluminescence were discussed with relation to the intrinsic and extrinsic defects.
24.	Ul Hassan Alvi, Naveed, et al. (author) The Fast and One-Step Growth of ZnO Nanorods on Cellulose Nanofibers for Highly Sensitive Photosensors 2023 In: Nanomaterials. - : Multidisciplinary Digital Publishing Institute (MDPI). - 2079-4991. ; 13:18 Journal article (peer-reviewed)abstract Cellulose is the most abundant organic material on our planet which has a key role in our daily life (e.g., paper, packaging). In recent years, the need for replacing fossil-based materials has expanded the application of cellulose and cellulose derivatives including into electronics and sensing. The combination of nanostructures with cellulose nanofibers (CNFs) is expected to create new opportunities for the development of innovative electronic devices. In this paper, we report on a single-step process for the low temperature (<100 °C), environmentally friendly, and fully scalable CNF-templated highly dense growth of zinc oxide (ZnO) nanorods (NRs). More specifically, the effect of the degree of substitution of the CNF (enzymatic CNFs and carboxymethylated CNFs with two different substitution levels) on the ZnO growth and the application of the developed ZnO NRs/CNF nanocomposites in the development of UV sensors is reported herein. The results of this investigation show that the growth and nature of ZnO NRs are strongly dependent on the charge of the CNFs; high charge promotes nanorod growth whereas with low charge, ZnO isotropic microstructures are created that are not attached to the CNFs. Devices manufactured via screen printing/drop-casting of the ZnO NRs/CNF nanocomposites demonstrate a good photo-sensing response with a very stable UV-induced photocurrent of 25.84 µA. This also exhibits excellent long-term stability with fast ON/OFF switching performance under the irradiance of a UV lamp (15 W).
25.	Ul Hassan Alvi, Naveed, et al. (author) Toward Photoactive Wallpapers Based on ZnO-Cellulose Nanocomposites 2023 In: Global Challenges. - : WILEY-V C H VERLAG GMBH. - 2056-6646. ; 7 Journal article (peer-reviewed)abstract The quest for eco-friendly materials with anticipated positive impact for sustainability is crucial to achieve the UN sustainable development goals. Classical strategies of composite materials can be applied on novel nanomaterials and green materials. Besides the actual technology and applications also processing and manufacturing methods should be further advanced to make entire technology concepts sustainable. Here, they show an efficient way to combine two low-cost materials, cellulose and zinc oxide (ZnO), to achieve novel functional and "green" materials via paper-making processes. While cellulose is the most abundant and cost-effective organic material extractable from nature. ZnO is cheap and known of its photocatalytic, antibacterial, and UV absorption properties. ZnO nanowires are grown directly onto cellulose fibers in water solutions and then dewatered in a process mimicking existing steps of large-scale papermaking technology. The ZnO NW paper exhibits excellent photo-conducting properties under simulated sunlight with good ON/OFF switching and long-term stability (90 minutes). It also acts as an efficient photocatalyst for hydrogen peroxide (H2O2) generation (5.7 x 10(-9) m s(-1)) with an envision the possibility of using it in buildings to enable large surfaces to spontaneously produce H2O2 at its outer surface. Such technology promise for fast degradation of microorganisms to suppress the spreading of diseases.
26.	Usman Ali, Syed, et al. (author) Selective potentiometric determination of uric acid with uricase immobilized on ZnO nanowires 2011 In: Sensors and actuators. B, Chemical. - : Elsevier Science B.V., Amsterdam.. - 0925-4005 .- 1873-3077. ; 152:2, s. 241-247 Journal article (peer-reviewed)abstract In this study, a potentiometric uric acid biosensor was fabricated by immobilization of uricase onto zinc oxide (ZnO) nanowires. Zinc oxide nanowires with 80-150 nm in diameter and 900 nm to 1.5 mu m in lengths were grown on the surface of a gold coated flexible plastic substrate. Uricase was electrostatically immobilized on the surface of well aligned ZnO nanowires resulting in a sensitive, selective, stable and reproducible uric acid biosensor. The potentiometric response of the ZnO sensor vs Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (1-650 mu M) suitable for human blood serum. By applying a Nafion (R) membrane on the sensor the linear range could be extended to 1-1000 mu M at the expense of an increased response time from 6.25 s to less than 9 s. On the other hand the membrane increased the sensor durability considerably. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea.
27.	Willander, Magnus, et al. (author) Intrinsic White Light Emission from Zinc Oxide Nanorods Heterojunctions on Large Area Substrates 2011 In: Proceedings of SPIE Volume 7940. - Bellingham, Washington, USA : SPIE - International Society for Optical Engineering. - 9780819484772 Conference paper (other academic/artistic)abstract Zinc oxide (ZnO) and especially in the nanostructure form is currently being intensively investigated world wide for the possibility of developing different new photonic devices. We will here present our recent findings on the controlled low temperature chemical growth of ZnO nanorods (NRs) on different large area substrates. Many different heterojunctions of ZnO NRs and p-substrates including those of crystalline e. g. p-GaN, p-SiC or amorphous nature e. g. p-polymer coated plastic and p-polymer coated paper will be shown. Moreover, the effect of the p-electrode of these heterojunctions on tuning the emitted wavelength and changing the light quality will be discussed. An example using ZnO NR/p-GaN will be shown and the electrical and electro-optical characteristics will be analyzed. For these heterojunctions the effect of post growth annealing and its effect on the electroluminescence (EL) spectrum will be shown. Finally, intrinsic white light emitting diodes based on ZnO NRs on foldable and disposable amorphous substrates (plastic and paper) will also be presented.

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