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One‐Pot Exfoliation of Graphitic C <sub/>3</sub> N <sub/>4</sub> Quantum Dots for Blue QLEDs by Methylamine Intercalation
摘要： Here, a simplified synthesis of graphitic carbon nitride quantum dots (g-C3N4-QDs) with improved solution and electroluminescent properties using a one-pot methylamine intercalation–stripping method (OMIM) to hydrothermally exfoliate QDs from bulk graphitic carbon nitride (g-C3N4) is presented. The quantum dots synthesized by this method retain the blue photoluminescence with extremely high fluorescent quantum yield (47.0%). As compared to previously reported quantum dots, the g-C3N4-QDs synthesized herein have lower polydispersity and improved solution stability due to high absolute zeta-potential (?41.23 mV), which combine to create a much more tractable material for solution processed thin film fabrication. Spin coating of these QDs yields uniform films with full coverage and low surface roughness ideal for quantum dot light-emitting diode (QLED) fabrication. When incorporated into a functional QLED with OMIM g-C3N4-QDs as the emitting layer, the LED demonstrates ≈60× higher luminance (605 vs 11 Cd m?2) at lower operating voltage (9 vs 21 V), as compared to the previously reported first generation g-C3N4 QLEDs, though further work is needed to improve device stability.
关键词： graphitic carbon nitride,quantum dot light-emitting diodes,metal-free semiconductors,hydrothermal exfoliation
更新于2025-09-19 17:13:59
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Facile designing and assessment of photovoltaic performance of hydrothermally grown kesterite Cu2ZnSnS4 thin films: Influence of deposition time
摘要： Herein, low cost precursor source Cu2ZnSnS4 (CZTS) nanocrystalline thin films at various reaction time were successfully synthesized via one step hydrothermal route. Hydrothermal route was employed to achieve control over the size and grain growth of CZTS films. As deposited CZTS films were analyzed for its optoelectronic, structural, morphological and electrochemical properties to investigate the effect of hydrothermal reaction time on growth and photovoltaic performance. The hydrothermal synthesis promoted to high absorption (104 cm?1) of the CZTS film with a decrease in optical band gap energy from 1.52 eV to 1.41 eV. Structural study revealed that, improved crystallinity with A1 mode of vibration for pure phase kesterite CZTS structure. Morphological transition was observed from nanograins to well grown and compact nanospheres. Compositional analysis illustrates, stoichiometric CZTS film formation with the desired valence state of Cu+, Zn2+, Sn4+ and S2? elements. Current density-voltage (J-V) measurement of FTO/CZTS/(0.3 M Eu3+/Eu2+)/Graphite cell configuration shows, highest photocurrent of 2.60 mA/cm2 and open circuit voltage of 754 mV was observed for CZTS4 sample with best photoconversion efficiency (η) 3.21% under illumination of 30 mW/cm2 light intensity. Electron impedance spectroscopy (EIS) showed that, generation of lower charge transfer resistance (Rct) with increase in reaction time.
关键词： Photoelectrochemical (PEC) cell,Cu2ZnSnS4 thin films,Electron impedance spectroscopy,Hydrothermal route
更新于2025-09-19 17:13:59
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Low-temperature Synthesized Nba??doped TiO <sub/>2</sub> Electron Transport Layer enabling High-efficiency Perovskite Solar Cells by Band Alignment Tuning
摘要： An Nb-doped TiO2 (Nb-TiO2) film comprising a double structure stacked with a bottom compact layer and top mesoporous layers was synthesized by treating a Ti precursor-coated substrate using a one-step low-temperature steam-annealing (SA) method. SA-based Nb-TiO2 films possess high crystallinity and conductivity, and that allows better control over the conduction band (CB) of the TiO2 for electron transport layer (ETL) of the perovskite solar cells (PSCs) by the Nb doping level. Optimization of power conversion efficiency (PCE) for the Nb-TiO2 based ETL was combined with CB level tuning of the mixed-halide perovskite by changing the Br/I ratio. This band offset management enabled to establish the most suitable energy levels between ETL and perovskites. This method was applied to reduce the bandgap of perovskite to enhance photocurrent density while maintaining a high open-circuit voltage. As a result, the optimal combination of 5 mol% Nb-TiO2 ETL and 10 mol%-Br in the mixed-halide perovskite exhibited high photovoltaic performance for low-temperature device fabrication, achieving a high yield PCE of 21.3%.
关键词： low-temperature process,solvent-free hydrothermal synthesis,electron transport layer,steam-annealing method,Perovskite solar cell,niobium-doped TiO2
更新于2025-09-19 17:13:59
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Hydrothermal growth of n-ZnO films on a patterned p-GaN epilayer and its application in heterojunction light-emitting diodes
摘要： The hydrothermal growth (HTG) of crystalline n-ZnO ?lms on both the nonpatterned and patterned p-GaN epilayers with a honeycomb array of etched holes is demonstrated, and its application in n-ZnO/p-GaN heterojunction light-emitting diodes (HJ-LEDs) is reported. The results reveal that an HTG n-ZnO ?lm on a patterned p-GaN layer exhibits a high-quality single crystal with FWHMs of 0.463 and 0.983° obtained from a ω-rocking curve and a ?-scan pattern, respectively, which are much better than those obtained on a nonpatterned p-GaN layer. In addition, the n-ZnO/patterned p-GaN HJ-LED exhibited a much better rectifying diode behavior owing to having a higher n-ZnO ?lm crystallinity quality and an improved interface with the p-GaN layer. Strong violet and violet-blue lights emitted from the n-ZnO/patterned p-GaN HJ-LED at around 405, 412, and 430 nm were analyzed.
关键词： crystallinity quality,n-ZnO films,heterojunction light-emitting diodes,hydrothermal growth,p-GaN epilayer
更新于2025-09-19 17:13:59
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Green fluorescent carbon quantum dots functionalized with polyethyleneimine, and their application to aptamer-based determination of thrombin and ATP
摘要： Brightly fluorescent carbon quantum dots coated with polyethylenimine (PEI-CDs) were prepared using malic acid and PEI as the precursors. The PEI-CDs have a high quantum yield (41%) and green emission (peaking at 502 nm under 430 nm excitation), both of which are not affected by high ionic strength. The PEI-CDs have a positive charge at physiological pH values and can electrostatically bind aptamers with their negative charge. This is shown for aptamers binding thrombin or ATP. Binding of aptamers results in quenching of fluorescence. If thrombin or ATP are introduced, the respective aptamer will bind them, and the complex is then released from the PEI-CDs. Fluorescence increases in proportion to the analyte concentration. Under optimized conditions, thrombin and ATP can be sensitively and selectively detected by fluorometry with lower detection limits of 1.2 and 13 nM, respectively. The assay was successfully applied to the determination of thrombin and of ATP in spiked serum samples.
关键词： Aptamer sensor,Thrombin detection,Serum analysis,Green luminescent,PEI-CDs,Malic acid,Polyethylenimine,Fluorescence assay,ATP detection,Hydrothermal reaction
更新于2025-09-19 17:13:59
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The Impact of Growth Temperature on Nanorod Morphology and Optical Properties for CH3NH3PbI3 Perovskite Solar Cell Device Application
摘要： Perovskite solar cells have been studied intensively by photovoltaic researchers in recent years due to their ability to absorb proper light. This research describes the CH3NH3PbI3 perovskite solar cell fabrication process. The solar cell structure is composed of ITO/ZnO seed layer/ZnO NRs/CH3NH3PbI3, with ZnO NRs as a nano shaped stem layer where perovskite crystals form. ZnO NRs have been successfully synthesized on the ITO substrate by a hydrothermal method. The ZnO seed layer is synthesized by a spin coating method in a mixture of zinc acetate dihydrate solution and ethanol. ZnO NRs were synthesized using hexamethylenetetramine (HMT) and zinc nitrate with a 1:1 molar ratio for 6 h. Some variations in growth temperature used were 80, 90 and 100 oC with a zinc nitrate concentration of 50 mM. Similarly, perovskite film devices are made through a two-step deposition using PbI2 and CH3NH3I as the main ingredients. The effects of synthesis conditions on ZnO NRs film and perovskite film devices were systematically investigated to look at the structure, morphology, optical properties of films and electrical properties of films using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), IV meter and LCR AC meter. The SEM results show that as the temperature increases, the size of the diameter and length of the rods are increased. The large rod diameter and length decrease the value of energy band gap. ZnO NRs synthesized with 50 mM concentrations at 100 oC showed the best results regarding morphology and optical properties. The film has a diameter size of 365 nm, length of the rod of 5.1 μm, and an energy band gap of 3.15 eV. The diffraction results indicate a PbI2 peak implying that it has not been converted to CH3NH3PbI3. The existence of PbI2 is suspected of opening the gap of recombination so that the current value measured by I-V meter is relatively small (0.186×10-6 μA). The low current that was generated indicates a high dielectric value and resistivity so that the light absorbing ability is less than perfect.
关键词： hydrothermal,perovskite solar cell,seed layer,ZnO nanorods
更新于2025-09-19 17:13:59
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Controlled Fabrication of K2Ti8O17 Nanowires for Highly Efficient and Ultrafast Adsorption towards Methylene Blue
摘要： Advanced adsorbents need high adsorption rate and superior adsorption capability to clean up the organic methylene blue (MB) from wastewater. We prepared K2Ti8O17 nanowires grown along [0 1 0] direction with a one-step hydrothermal method. The K2Ti8O17 nanowires with tens of nanometers in diameter and tens of micrometers in length were achieved with smooth surfaces and twisted wire-like morphology. The K2Ti8O17 nanowires exhibit high uptake capacity of ～208.8 mg·g?1 in the MB removal under equilibrium pH = 7. The adsorption equilibriums of MB onto K2Ti8O17 adsorbent is achieved with 97% removal rate MB within only ~21 min, which is the shortest adsorption time among the recent reported inorganic adsorbents towards MB. The adsorption process has a good agreement with the well-known pseudo-second-order kinetic model (k2 = 0.2) and the Langmuir isotherm model. The FTIR measurements suggest that the adsorption can be assigned to the hydrogen bonding and electrostatic attraction between MB and K2Ti8O17. This ultrafast removal ability owns to the larger (0 2 0) interplanar spacing and zigzag surface structure of the nanowires, which provide abundant active adsorption sites. Thermodynamic parameters reflect the spontaneous, exothermic and feasible uptake of MB. Besides, K2Ti8O17 nanowires enjoy high adsorptive ability for chromium (VI) ions and photocatalytic removal towards NO. This work highlights the great significance of K2Ti8O17 nanowires as a low cast promising material used for adsorptive elimanation of organic contaminations in fast water purification on a large scale.
关键词： Hydrothermal synthesis,Tunnel-layered structure,Adsorption capability,K2Ti8O17 nanowires,Thermodynamics,Kinetics,Isotherms
更新于2025-09-16 10:30:52
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Silicate-germanates with the doubled mica-like layers [Pb(Si,Ge)O4]2-∞∞ in centrosymmetric Rb2Pb2[(Ge0.33Si0.67)2O7] and isolated in acentric, optically nonlinear Li6Pb2[(Ge0.4Si0.6)O4]2(OH)2
摘要： Silicate-germanates, Rb2Pb2[(Si0.67Ge0.33)2O7], P m1, and Li6Pb2[(Ge0.4Si0.6)O4]2(OH)2, P63mc, were synthesized in the multi-component hydrothermal systems. According to single crystal XR data, both structures contain identical mica-like layers [Pb(Ge,Si)O4]2- ∞∞, double or single, comprised of [(Si,Ge)O4]4--tetrahedra and umbrella-like groups [PbO3]4-: the latter play a unique role of (Si,Ge)-tetrahedra being of the same charge, dimension and the Pb-lone-pair as the forth apex. Predicted earlier polar ortho-silicate structure appears with small Li atom, while the centrosymmetric diortho-silicate structure type A2Pb2[B2O7] is stable with large A = K, Rb, Cs. Layers with {Li3O7}11- atomic clusters separate single tetrahedral layers. Under Nd:YAG laser illumination the powder of acentric Li,Pb-silicate-germanate yields intensive light of second harmonic. The maximum second harmonic intensity 10 times more in comparison with quartz standard is achieved in the powder with a grain size of about 20 μm. The space-averaged second-order nonlinear coefficient <d> = 1.1 pm/V. The comparably high optical nonlinearity is connected with the one-side directed umbrella-like polar units [PbO3]4- in polar structure of the Li,Pb-silicate-germanate.
关键词： materials design,structure,hydrothermal synthesis,lead-silicate-germanate,structure-properties relations,optical nonlinearity
更新于2025-09-16 10:30:52
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Controlled Hydrothermal Synthesis of K<sub>2</sub>Ti<sub>6</sub>O<sub>13</sub> Nanowires and their Photo-Electronic Response
摘要： A hydrothermal method using tetrabutyl titanate and KOH as reactants for synthesis of K2Ti6O13 nanowires was developed, obtaining nanowires with a uniform diameter around 10nm. It is shown that the hydrothermal temperature and the KOH concentration have little influence in tuning the growth of K2Ti6O13 nanowires. By changing the time for hydrothermal reaction, the length of K2Ti6O13 nanowires can be controlled from several dozen of nanometers to several hundreds of nanometers. The as-prepared K2Ti6O13 nanowires exhibit a wide and strong absorption band in the ultraviolet range (around 200~300 nm), and stable photocurrent of 0.5μA/cm2, which might suggest potential applications in solar cell and water splitting.
关键词： photo-electronic response,hydrothermal synthesis,K2Ti6O13 nanowires
更新于2025-09-16 10:30:52
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Modulation doping of absorbent cotton derived carbon dots for quantum dot-sensitized solar cells
摘要： In order to improve the power conversion efficiency (PCE) of quantum dot-sensitized solar cells (QDSC), a series of absorbent cotton derived carbon quantum dots (CQDs) with different dopants (namely carbamide, thiourea, and 1,3-diaminopropane) have been successfully synthesized by a one-pot hydrothermal method. The average particle sizes of the three doped CQDs are 1.7 nm, 5.6 nm, and 1.4 nm respectively, smaller than that of the undoped ones (24.2 nm). The morphological and structural characteristics of the four CQDs have been studied in detail. In addition, the three doped CQDs exhibit better optical properties compared with the undoped ones in the UV-vis and PL spectra. Then CQD-based QDSC are experimentally fabricated, showing that the short current density (Jsc) and open circuit voltage (Voc) of the QDSC are distinctly improved owing to the dopants. Especially the QDSC with the 1,3-diaminopropane doped CQD achieves the highest PCE (0.527%), 299% larger than that without dopant (0.176%). In order to highlight a reasonable mechanism, the UV-vis diffuse reflectance spectrum of CQD sensitized TiO2 and the calculated energy band structures of various CQDs are investigated. It’s found from the above analysis that the addition of carbamide, thiourea, and 1,3-diaminopropane is beneficial to obtain CQDs of smaller size, and with a smaller band gap and more nitrogenous or sulphureous functional groups, which enhance the light absorption performance and photo-excitation properties. The above factors are helpful to improve the Jsc of QDSC. Nitrogen, acting as a donor to the CQDs, will assist the sensitized photoanode with a higher Fermi level, resulting in a larger Voc of the QSDC. Finally this study builds the relation among the microstructure of the CQDs, three characteristics of the CQDs (namely the spectra, energy band structure and functional groups) and the photoelectric properties of the QDSC, which will provide guidance for the modulation doping of CQDs to improve the PCE of QDSC.
关键词： dopants,carbon quantum dots,hydrothermal method,power conversion efficiency,quantum dot-sensitized solar cells
更新于2025-09-16 10:30:52