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AIP Conference Proceedings [AIP Publishing ADVANCES IN BASIC SCIENCE (ICABS 2019) - Bahal, India (7–9 February 2019)] ADVANCES IN BASIC SCIENCE (ICABS 2019) - Synthesis and optical properties of Zn(II) doped graphene quantum dots: Blue to purple emission
摘要： The Graphene Quantum dots (GQDs), fragments of graphene have attracted considerable attention in recent years due to the size, edge effects, quantum confinement and heteroatom doping. The doping of graphene based materials can effectively tune their intrinsic properties, including electronic and optical properties, surface and local chemical reactivity. Herein, we present a comprehensive study of ZnO doped GQDs prepared by a facile hydrothermal method by using ZnO and Graphne Oxide (GO) as a source materials. All the synthesized materials were characterized by UV-Visible Spectroscopy (UV-Vis), Raman Spectroscopy, Fourier Transform Infrared (FT-IR) and Photoluminescence (PL). The morphological characterizations were confirmed by transmission electron microcopy images (TEM). The hydrothermally synthesized material had a size of 5-20 nm by uniform doping of zinc nanoparticles on graphene sheet. The results of PL of Zn(II)-GQDs showed a blue to purple emission with the variation in excitation wavelength from 280nm to 380nm. These doped GQDs were found to be an efficient approach with multicolor emission for biological applications and optoelectronic devices to make the environmental friendly, cost effective and easily scalable.
关键词： optical properties,photoluminescence,Graphene Quantum dots,hydrothermal method,Zn(II) doping
更新于2025-09-12 10:27:22
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Three-dimensional ZnO nanorods growth on ZnO nanorods seed layer for high responsivity UV photodetector
摘要： Three-dimensional ZnO nanorods (NRs) were synthesized by hydrothermal method on ZnO seed layer including horizontal ZnO NRs. The ZnO seed layers consist of different values of NRs were synthesized by spin-coating. The different seed layers and ZnO nanorods arrays were characterized using field emission scanning electron microscopy, X-ray diffraction. Horizontally dispersed NRs on the substrate formed an overlapping junction structure into seed layer as ZnO NRs network. NRs grown on the seed layer including horizontal NRs were oriented in different directions to form three-dimensional ZnO NRs in flower shape. The electrical resistance of sensors based NRs array decreased dramatically with increasing NRs added to ZnO seed layer. Results show that ultraviolet photocurrent increased from 1.7 to 23 μA which is suitable for fabrication of practical photodevices.
关键词： UV photodetector,ZnO nanorods,seed layer,photocurrent,hydrothermal method
更新于2025-09-12 10:27:22
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ε-Poly-L-lysine-protected Ti3C2 MXene quantum dots with high quantum yield for fluorometric determination of cytochrome c and trypsin
摘要： Titanium carbide quantum dots functionalized with ε-poly-L-lysine (PLL) were synthesized by sonication cutting and hydrothermal synthesis. The deprotonated Ti3C2 MXene quantum dots (Ti3C2 MQDs) exhibit excitation wavelength-dependent blue photoluminescence with typical excitation/emission peaks at 330/415 nm and a quantum yield of 22% due to strong quantum confinement. The fluorescence of ε-poly-L-lysine protected Ti3C2 MQDs (PLL-protected Ti3C2 MQDs) is reduced via an inner filter effect after the addition of cytochrome c (cyt-c). Response to cyt-c is linear in the 0.2 to 40 μM concentration range and the detection limit is 20.5 nM. In the presence of trypsin, cyt-c is hydrolyzed to small peptides, and the Fe3+ ion in cyt-c probably is reduced to Fe2+ with the aid of the digestive enzyme. This results in the restoration of the blue fluorescence of the modified MQDs. Fluorescence increases linearly in the 0.5 to 80 μg mL?1 trypsin concentration range with the detection limit of 0.1 μg mL?1. The method was successfully applied to the determination of cyt-c and trypsin in spiked serum samples.
关键词： Hydrothermal method,Inner filter effect,Fluorescence,Trypsin,Cytochrome c,Ti3C2 MXene quantum dots
更新于2025-09-12 10:27:22
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Facile preparation of high fluorescent carbon quantum dots from orange waste peels for nonlinear optical applications
摘要： A facile and eco‐friendly hydrothermal method was used to prepare carbon quantum dots (CQDs) using orange waste peels. The synthesized CQDs were well dispersed and the average diameter was 2.9 ± 0.5 nm. Functional group identification of the CQDs was confirmed by Fourier transform infrared spectrum analysis. Fluorescence properties of the synthesized CQDs exhibited blue emission. The fluorescence quantum yield of the CQDs was around 11.37% at an excitation wavelength of 330 nm. The higher order nonlinear optical properties were examined using a Z‐scan technique and a continuous wave laser that was operated at a wavelength of 532 nm. Results demonstrated that the synthesis of CQDs can be considered as promising for optical switching devices, bio‐scanning, and bio‐imaging for optoelectronic applications.
关键词： Z‐scan analysis,fluorescence quantum yield,CQDs,HR‐TEM,hydrothermal method
更新于2025-09-11 14:15:04
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The enhanced light harvesting performance of dye-sensitized solar cells based on ZnO nanorod-TiO2 nanotube hybrid photoanodes
摘要： In this study, TiO2/ZnO hybrid nanocomposites (TZ) were fabricated by two step synthesis route for potential applications as photoanode in dye sensitized solar cells (DSSC). Titania nanotubes were grown on titanium sheets by electrochemical oxidation. ZnO nanorods were decorated with hydrothermal method by equimolar (0.1M) precursors on TiO2 nanotubes. Hydrothermal temperatures values were changed to find the optimal ZnO hydrothermal reaction temperature can dramatically enhance the decoration density to increase photo conversion efficiency. The characterization of the photoanode was reached 1.67% for hydrothermal temperature of 130 °C which is twofold performance of TZ photoanodes. The photo conversation efficiency of DSSC by TZ were decorated with hydrothermal method by equimolar (0.1M) precursors on TiO2 photoanodes was made using FE-SEM, XRD and XPS technics. The results show that, higher than that of DSSC by TiO2 nanotubes (0.81%). The improvement in photo conversation conversion efficiency can be assigned to synergetic effect in TZ photoanode, lower recombination rate and charge transfer resistance.
关键词： TiO2 nanotube array,light harvesting,hydrothermal method,Zinc oxide,DSSC
更新于2025-09-11 14:15:04
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Graphene quantum dot vertical cavity surface emitting lasers
摘要： Nonzero-bandgap graphene quantum dots (GQDs) are novel optical gain materials promising for solution-processed light sources with high cost efficiency and device performance. To date, there have only been a few reports on the realization of GQDs-based lasers. Herein, we demonstrate for the first time room-temperature lasing emission with green gamut from GQDs in a vertical optical cavity composed of Ta2O5/SiO2 dielectric distributed Bragg reflectors (DBRs). The lasing is enabled by the unique design of the DBR which not only provides a wide stopband spectrally overlapping with the emission of the GQDs but also allows high transmittance of optical excitation in the UV-light region. This demonstration is a clear evidence of the use of GQDs as optical gain materials and represents an important step forward toward their potential applications in wide-gamut laser displays and projectors.
关键词： Vertical Cavity Surface Emitting Laser,Graphene Quantum Dots,Green Gap,Microwave-Assisted Hydrothermal Method,Distributed Bragg Reflectors (DBRs)
更新于2025-09-11 14:15:04
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Computational Chemistry Meets Experiments for Explaining the Geometry, Electronic Structure, and Optical Properties of Ca <sub/>10</sub> V <sub/>6</sub> O <sub/>25</sub>
摘要： In this paper, we present a combined experimental and theoretical study to disclose, for the first time, the structural, electronic, and optical properties of Ca10V6O25 crystals. The microwave-assisted hydrothermal (MAH) method has been employed to synthesize these crystals with different morphologies, within a short reaction time at 120 °C. First-principle quantum mechanical calculations have been performed at the density functional theory level to obtain the geometry and electronic properties of Ca10V6O25 crystal in the fundamental and excited electronic states (singlet and triplet). These results, combined with the measurements of X-ray diffraction (XRD) and Rietveld refinements, confirm that the building blocks lattice of the Ca10V6O25 crystals consist of three types of distorted 6-fold coordination [CaO6] clusters: octahedral, prism and pentagonal pyramidal, and distorted tetrahedral [VO4] clusters. Theoretical and experimental results on the structure and vibrational frequencies are in agreement. Thus, it was possible to assign the Raman modes for the Ca10V6O25 superstructure, which will allow us to show the structure of the unit cell of the material, as well as the coordination of the Ca and V atoms. This also allowed us to understand the charge transfer process that happens in the singlet state (s) and the excited states, singlet (s*) and triplet (t*), generating the photoluminescence emissions of the Ca10V6O25 crystals.
关键词： structural properties,electronic properties,Ca10V6O25,microwave-assisted hydrothermal method,photoluminescence,optical properties
更新于2025-09-10 09:29:36
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Bioinspired Synthesis of Carbon Dots/g-C <sub/>3</sub> N <sub/>4</sub> Nanocomposites for Photocatalytic Application
摘要： This study reports a fast and green preparative strategy to synthesize water soluble and fluorescent carbon quantum dots (CQDs) through hydrothermal method by using low cost organic waste of human fingernails as the carbon precursor for the first time. The coupling of CQD with pure carbon nitride (g-C3N4) was further explored to enhance the latter’s performance in photocatalysis of 2,4-dicholorophenol (2,4-DCP), a toxic and recalcitrant compound mostly released from industrial effluent. Such coupling overcame the weakness of pure g-C3N4 in photocatalysis process by broadening its visible light absorption and promoting the charge separation. As a result, the removal rate of CQD/ g-C3N4(10) was up to 71.53%, which was approximately 1.5 times higher than that of pure g-C3N4 under sunlight irradiation. The morphological structure, optical properties and chemical compositions of CQDs/g-C3N4 composites were characterized using various spectroscopic techniques including field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray (EDX) and Ultraviolet-visible diffuse reflectance spectra (UV-DRS).
关键词： Photocatalysis,Hydrothermal method,Carbon quantum dots,4-dichlorophenol,2,g-C3N4
更新于2025-09-10 09:29:36
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Influences of reaction temperature, holding time and S/Zn molar ratio on structure, morphology, optical and electrical properties of ZnS nanoparticles synthesized by hydrothermal method
摘要： ZnS nanoparticles were synthesized by hydrothermal method. The influences of reaction temperature, holding time and S/Zn molar ratio on the structure, morphology, optical and electrical properties of ZnS nanoparticles were studied systematically at the range of 90?°C to 180?°C, 6?h to 15?h and 1:2 to 2.5:1, respectively. The results indicate that the reaction temperature, holding time and S/Zn molar ratio have no influence on phase structure. All the samples belong to zinc blende cubic structure of ZnS. However, the reaction temperature has strong influences on the growth of crystals, optical and electrical properties due to LaMer theory and two-stage growth kinetics. When the reaction temperature increases from 90?°C to 180?°C, the crystallite sizes increase from 7.0?nm to 9.7?nm and the average particle sizes decrease from 21?nm to 14?nm; the emission peaks are red shifted from 445?nm to 460?nm and the emission intensity is increased by 4.4 times; the dielectric constant and dielectric loss decrease from 4.86 to 4.71 and 2.86 × 104 to 2.70 × 104, respectively. While, the holding time has slight influences on the growth of crystals, optical and electrical properties. And the emission band and emission intensity of ZnS nanoparticles can be adjusted by the S/Zn molar ratio. When the S/Zn molar ratio is less than 1:1 or equal to 1:1, the emission bands range from 400?nm to 600?nm centered at ~ 450?nm. When the S/Zn molar ratio is greater than 1:1, the emission bands range from 400?nm to 700?nm centered at ~ 540?nm.
关键词： Holding time,Optical properties,Reaction temperature,Hydrothermal method,S/Zn molar ratio,ZnS nanoparticles,Electrical properties
更新于2025-09-10 09:29:36
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Highly Sensitive Ammonia Sensors Based on Ag-Decorated WO <sub/>3</sub> Nanorods
摘要： In this paper, WO3 nanorods are successfully synthesized via a one-step hydrothermal method, and then, silver nanoparticles are deposited on the WO3 surface by in situ photoreduction method to obtain Ag/WO3 gas sensitive materials. WO3 and Ag/WO3 are characterized by scanning electron microscope techniques, transmission electron microscope, and X-ray diffraction. The experimental results indicated that Ag nanoparticles have an important effect on the gas response of WO3 . The Ag/WO3 sensor greatly improves the selectivity and response compared to the traditional WO3 sensor; the response is 300 for 100 ppm ammonia when the Ag/WO3 sensor operates at the optimum operating temperature. The Ag/WO3 sensor can respond to 50 ppb ammonia.
关键词： nanoparticle,One-step hydrothermal method,gas sensing mechanism,high sensitivity
更新于2025-09-10 09:29:36