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Unraveling the impact of the Pd nanoparticle@BiVO <sub/>4</sub> /S-CN heterostructure on the photo-physical & opto-electronic properties for enhanced catalytic activity in water splitting and one-pot three-step tandem reaction
摘要： Pd nanoparticles embedded SBVCN-37 heterostructure photocatalyst is synthesized and employed in the water splitting reaction and for the synthesis of imines via one-pot tandem reaction involving photocatalytic reduction of nitrobenzene, oxidation of benzyl alcohol, followed by condensation reaction between them. Embedded Pd nanoparticles (mean diameter ~ 5-7 nm) act as an electron mediator and enhance the catalytic activity during oxidation and reduction reactions. Experimental results confirm that the light induced holes owing to its favourable redox potential oxidize N2H4 to N2 and liberate H+ ions that subsequently react with photogenerated electrons and facilitate the nitrobenzene reduction. The obtained quantum yield for benzyl alcohol oxidation and nitrobenzene reduction are calculated to be (2.08 %) and (6.53 %) at λ = 420 nm light illumination. The obtained apparent quantum yields for OER and HER are calculated to be 10.22 % and 12.72 % at 420 nm indicating the excellent potentiality of the presently investigated photocatalyst for solar fuel production. Photoelectrochemical (PEC) and time resolved & steady state photoluminescence measurements reveal that an optimum amount of Pd nanoparticles over SBVCN-37 is the crucial factor for achieving the highest photocurrent response, the lowest charge transfer resistance, and the efficient carrier’s mobility alteration leading to a prominent catalytic activity. Further, Mott-Schottky (M-S) analysis confirms that the deposition of Pd nanoparticles effectively reduces the over-potential and fine-tunes the band edge potential required for HER and OER reactions, independently.
关键词： Tandem Reaction,BiVO4,Benzyl Alcohol Oxidation,Apparent Quantum Yield,Nitrobenzene Reduction,g-C3N4,Photocatalytic H2 and O2 Production
更新于2025-09-19 17:15:36
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Harnessing Brightness in Naphthalene Diimides
摘要： The development of brightly emissive compounds is of great research and commercial interest, with established and emerging applications across chemistry, biology, physics, medicine and engineering. Among the many types of molecules available, naphthalene diimides have been widely used for both fundamental photophysical studies and in practical applications that utilise information readout. The monomeric naphthalene diimide is weakly fluorescent, however through various methods of core-derivatisation, it can be developed to be highly fluorescent and further functionalised to add utility. In this review, we highlight recent advances made in naphthalene diimide chemistry that have led to development of molecules with improved optical properties, and the design strategies utilised to produce bright fluorescence emission as small molecules or in supramolecular architectures.
关键词： naphthalene diimides,fluorescence,molecular brightness,absorption coefficient,quantum yield
更新于2025-09-19 17:15:36
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Ultrahigh-efficiency aqueous flat nanocrystals of CdSe/CdS@Cd <sub/>1?x</sub> Zn <sub/>x</sub> S colloidal core/crown@alloyed-shell quantum wells
摘要： Colloidal semiconductor nanoplatelets (NPLs) are highly promising luminescent materials owing to their exceptionally narrow emission spectra. While high-efficiency NPLs in non-polar organic media can be obtained readily, NPLs in aqueous media suffer from extremely low quantum yields (QYs), which completely undermines their potential, especially in biological applications. Here, we show high-efficiency water-soluble CdSe/CdS@Cd1?xZnxS core/crown@shell NPLs formed by layer-by-layer grown and composition-tuned gradient Cd1?xZnxS shells on CdSe/CdS core/crown seeds. Such control of shell composition with monolayer precision and effective peripheral crown passivation, together with the compact capping density of short 3-mercaptopropionic acid ligands, allow for QYs reaching 90% in water, accompanied by a significantly increased photoluminescence lifetime (～35 ns), indicating the suppression of nonradiative channels in these NPLs. We also demonstrate the controlled attachment of these NPLs without stacking at the nanoscale by taking advantage of their 2D geometry and hydrophilicity. This is a significant step in achieving controlled assemblies and overcoming the stacking process, which otherwise undermines their film formation and performance in optoelectronic applications. Moreover, we show that the parallel orientation of such NPLs achieved by the controlled attachment enables directed emission perpendicular to the surface of the NPL films, which is highly advantageous for light extraction in light-emitting platforms.
关键词： nanoplatelets,quantum yield,core/crown@shell,aqueous media,directed emission
更新于2025-09-19 17:15:36
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Extending the ?-electron conjugation in 2D planar graphitic carbon nitride: Efficient charge separation for overall water splitting
摘要： We report the direct overall pure water splitting by visible light excited graphitic carbon nitride incorporated with conjugated aromatic rings without using sacrificial agents. We fabricated the modified graphitic carbon nitride polymer samples by copolymerization of melamine with 2,4,6-triaminopyrimidine and 1,3,5-triaminobenzene, containing a few-carbon (pyrimidine) to all-carbon (benzene) aromatic rings. Solid state 13C NMR shows that the core molecular skeleton of g-C3N4 remained intact even after the incorporation of benzene and pyrimidine aromatic rings into g-C3N4 chemical structure. Upon substitution of benzene aromatic ring in the place of triazine ring, the optical band gap energy of g-C3N4 is narrowed down from 2.8 eV to 2.1 eV with negative shifts of valence and conduction bands and due to the formation of defects like nitrogen vacancies. The DFT calculations predict that the benzene doped carbon nitride polymer has localized charge densities over valence band maxima and conduction band minima in different parts of heptazine rings, which assist in reducing the recombination rate of the charge carriers. The benzene ring incorporated carbon nitride photoelectrode shows higher photocurrent with lesser charge transfer resistance than the parent g-C3N4 and pyrimidine doped g-C3N4 polymers. This demonstrates the importance of the extended conjugation in g-C3N4 due to the presence of aromatic benzene rings. This is further corroborated by photoluminescence and electron paramagnetic resonance measurements. As a result, the benzene ring incorporated carbon nitride is more active than the pyrimidine ring incorporated carbon nitride for solar water splitting. The benzene ring incorporated carbon nitride polymer directly splits water and generates about 7 μmol h-1 of hydrogen with apparent quantum yield of 1.6% at 450 nm in the absence of sacrificial reagents, achieving turnover number of 1.6.
关键词： turnover number,benzene,DFT calculations,Carbon nitride,apparent quantum yield,charge separation,pyrimidine,water splitting
更新于2025-09-19 17:15:36
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Photoluminescence in <i>m</i> -carborane–anthracene triads: a combined experimental and computational study
摘要： New hybrids synthesized by linking two anthracenyl units to the Ccluster atoms of a non- (4), a mono- (5) and a di-iodinated (6) m-carborane fragment through CH2 spacers, along with their full characterization, are reported. Noticeably, bonding the m-carborane fragment to the anthracene moieties produces a significant increase of more than two-fold in the intrinsic fluorescence quantum yield (fF) of the anthracene itself, with values of fF 4 60% in THF and fF 4 48% in toluene, although it does not alter the absorption and emission patterns of the fluorophore in solution. A red-shift of the emission maximum with respect to the solution is observed in the aggregate state (THF/H2O, 1 : 99 v/v), along with moderate quantum yields; compounds 4 and 5 show fF = 22 and 19%, respectively, whereas 6 has a lower value (fF = 8%). The di?erence between the fF values in the aggregate state has been attributed to the arrangement of dimers for each compound in the solid state structures. X-ray crystal structures of compounds 4 and 5 show the anthracene units to be roughly parallel, whereas such an arrangement is clearly disrupted in compound 6. Such di?erences have been analyzed by Hirshfeld surfaces, decomposed fingerprint plots for the three compounds and DFT calculations. The combined results from the supramolecular analyses and DFT studies support the idea that a less delocalized system in the case of 6 can be explained by the di?erent packing in the aggregate or solid state for this di-iodo-derivative. The observed arrangement of molecules of 6 seems to be related to a larger number of H(cid:2) (cid:2) (cid:2)I contacts, with respect to the non-iodinated or mono-iodinated compounds, 4 or 5. According to this assumption, there is a direct relationship between the structure in the solid state and the PL properties; in the m-carborane derivatives, small changes in their structures have caused variations in the photophysical properties, especially in the quantum e?ciency.
关键词： X-ray diffraction,anthracene,m-carborane,Hirshfeld surfaces,photoluminescence,DFT calculations,fluorescence quantum yield
更新于2025-09-19 17:15:36
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Intensification of UV-C treatment to remove emerging contaminants by UV-C/H2O2 and UV-C/S2O82?: Susceptibility to photolysis and investigation of acute toxicity
摘要： In this study, the degradation of four emerging contaminants losartan potassium (LP), furosemide (FRSM), caffeine (CAF), and carbendazim (CBZ) under UV-C, UV-C/H2O2, and UV-C/S2O8^2- was investigated. A comparative evaluation of the efficiency of UV-C/H2O2 and UV-C/S2O8^2- in the degradation of these target CECs has not yet been reported. Moreover, target compounds were submitted to UV-C/AOPs individually in pure water and their simultaneous degradation was investigated in real surface water. Evolution of the acute toxicity of each compound during treatment was evaluated using Alivibrio fischeri. Quantum yields were determined for LP (0.011–0.016), FRSM (0.024–0.092), CAF (0.0007–0.0009), and CBZ (0.0016–0.0036) at different pH values. UV-C/H2O2 and UV-C/S2O8^2- achieved more than 98% removal of all compounds within 600 mJ cm^-2, and pseudo-first-order kinetic constants (k′app) for the degradation reactions were up to seven times higher in the presence of these oxidants when compared to k′app values obtained for UV-C photolysis. k′app measured for UV-C/H2O2 were higher than those calculated for UV-C/S2O8^2- except in the case of LP. Acute toxicity analysis suggested the formation of toxic intermediates during the UV-C photolysis of LP and FRSM, and the degradation of LP via UV-C/S2O8^2- also enhanced acute toxicity although electric energy efficiency per order identified UV-C/S2O8^2- as the most efficient process for the removal of this compound. Finally, different transformation products obtained during the degradation of caffeine under the different UV-C AOPs suggested that distinct degradation routes were involved in each treatment tested.
关键词： Contaminants of emerging concern,Advanced oxidation processes,Quantum yield,Persulfate,UV-C process
更新于2025-09-19 17:15:36
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Photophysical Constants of the Tetraoxa[8]Circulene Molecule
摘要： The rate constants of photophysical processes (radiation rate constant, internal conversion rate constant, and quantum fluorescence yield) have been calculated for the tetraoxa[8]circulene molecule by the INDO/S, TDDFT, and CC2 methods. It is confirmed that the doubly degenerate triplet level Т2 and the level Т1 are located below the first singlet excited level S1. According to the selection rules for the angular momentum, the spin-orbit interaction between the levels S1 and T1 (S1 and T2) is equal to zero. Therefore, the internal conversion is the only nonradiative channel in this molecule. The results of calculations also demonstrate that values of the internal conversion rate constant and the quantum fluorescence yield obtained by the INDO/S method are incorrect.
关键词： heterocirculenes,quantum yield,nonradiative transition constants
更新于2025-09-19 17:15:36
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Dynamics and quantum yields of H <sub/>2</sub> + CH <sub/>2</sub> CO as a primary photolysis channel in CH <sub/>3</sub> CHO
摘要： The first experimental observation of the primary photochemical channel of acetaldehyde leading to the formation of ketene (CH2CO) and hydrogen (H2) molecular products is reported. Acetaldehyde (CH3CHO) was photolysed in a molecular beam at 305.6 nm and the resulting H2 product characterized using velocity-map ion (VMI) imaging. Resonance-enhanced multiphoton ionization (REMPI), via two-photon excitation to the double-well EF 1S+ g state, was used to state-selectively ionize the H2 and determine angular momentum distributions for H2 (n = 0) and H2 (n = 1). Velocity-map ion images were obtained for H2 (n = 0 and 1, J = 5), allowing the total translational energy release of the photodissociation process to be determined. Following photolysis of CH3CHO in a gas cell, the CH2CO co-fragment was identified, using Fourier transform infrared spectroscopy, by its characteristic infrared absorption at 2150 cm?1. The measured quantum yield of the CH2CO + H2 product channel at 305.0 nm is f = 0.0075 ± 0.0025 for both 15 Torr of neat CH3CHO and a mixture with 745 Torr of N2. Although small, this result has implications for the atmospheric photochemistry of carbonyls and this reaction represents a new tropospheric source of H2. Quasi-classical trajectory (QCT) simulations on a zero-point energy corrected reaction-path potential are also performed. The experimental REMPI and VMI image distributions are not consistent with the QCT simulations, indicating a non reaction-path mechanism should be considered.
关键词： FTIR,velocity-map imaging,atmospheric chemistry,hydrogen,quantum yield,REMPI,ketene,acetaldehyde,photodissociation
更新于2025-09-19 17:15:36
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Enhanced thermal stability of InP quantum dots coated with Al-doped ZnS shell
摘要： Colloidal InP quantum dots (QDs) have attracted a surge of interest as environmentally friendly light-emitters in downconversion liquid crystal displays and light-emitting diodes (LEDs). A ZnS shell on InP-based core QDs has helped achieve high photoluminescence (PL) quantum yield (QY) and stability. Yet, due to the difficulty in the growth of a thick ZnS shell without crystalline defects, InP-based core/shell QDs show inferior stability against QY drop compared to Cd chalcogenide precedents, e.g., CdSe/CdS core/thick-shell QDs. In this work, we demonstrate the synthesis of InP-based core/shell QDs coated with an Al-doped ZnS outer shell. QDs with an Al-doped shell exhibit remarkable improvement in thermal and air stability even when the shell thickness is below 2 nm, while the absorption and PL spectra, size, and crystal structure are nearly the same as the case of QDs with a pristine ZnS shell. X-ray photoelectron spectroscopy reveals that Al3+ in Al-doped QDs forms an Al-oxide layer at elevated temperature under ambient atmosphere. The as-formed Al-oxide layer blocks the access of external oxidative species penetrating into QDs and prevents QDs from oxidative degradation. We also trace the chemical pathway of the incorporation of Al3+ into ZnS lattice during the shell growth. Furthermore, we fabricate QD-LEDs using Al-doped and undoped QDs and compare the optoelectronic characteristics and stability.
关键词： quantum yield,QD-LEDs,photoluminescence,Al-doped ZnS shell,X-ray photoelectron spectroscopy,InP quantum dots,thermal stability
更新于2025-09-19 17:13:59
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High-efficiency perovskite nanocrystal light-emitting diodes <i>via</i> decorating NiO <sub/>x</sub> on the nanocrystal surface
摘要： Nickel oxides exhibit a great potential as hole transport layers for the fabrication of efficient perovskite light-emitting diodes (LEDs) due to their high carrier mobility and good energy band matching with perovskite nanocrystals. In this work, nickel oxides were directly decorated on the CsPbBr3 nanocrystal surface through adsorption and a sequential oxidation treatment. The resulting sample shows a high photoluminescence quantum-yield of 82%. The LED using CsPbBr3 nanocrystals with nickel oxides achieves a high external quantum efficiency (EQE) of up to 16.8% with a low turn-on voltage of 2.8 V, which is much superior to that of the counterpart LED based on pristine CsPbBr3 nanocrystals (EQE = 0.7%, turn-on voltage = 5.6 V). The excellent performance of the nickel oxide decorated CsPbBr3 nanocrystal device could be attributed to the better energy level matching between the decorated nanocrystals and the transport layers of the device and more balanced charge carrier injection. Furthermore, the operational lifetime of the nickel oxide decorated CsPbBr3 nanocrystal device is 40 times longer than that of the pristine CsPbBr3 nanocrystal device.
关键词： perovskite nanocrystals,photoluminescence quantum-yield,light-emitting diodes,external quantum efficiency,nickel oxides
更新于2025-09-19 17:13:59