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Synergistic the modulation of photon absorption capability and interfacial charge transfer of the photocatalyst are highly required for developing high-performance heterojunction photocatalysts. The ternary CdS-graphene quantum dots-titanate nanotubes (CdS-GQDs-TNTs) nanocomposite have been prepared by an in situ growth method. The physicochemical characterization reveals that the GQDs are firmly decorated on both inner and outer surface of TNT through the formation of Ti–O–C chemical bonding, and CdS QDs are loaded on the outer surface of TNTs through strong interfacial interaction. The intimate integrated CdS-GQDs-TNTs nanocomposite exhibits much superior photocatalytic performance toward H2 production compared with binary GQDs-TNTs and pure TNTs photocatalyst, which can be attributed to the combined interaction of the stronger visible light harvesting, the longer lifetime of photogenerated electron−hole pairs, faster interfacial charge transfer rate, fast and long-distance electron transport pass. The interfacial charge transfer mechanism of CdS-GQDs-TNTs ternary composite are proposed based on photoelectrochemical measurements.

Epitaxial PbTiO3 films with a smooth and dense surface were fabricated by a promising hydrothermal synthesis on an Nb:SrTiO3(100) substrate. The resulting coated substrate was used to fabricate a Pt/PbTiO3/Nb:SrTiO3 heterostructure device. The device exhibited a multilevel storage capacity with an appropriate R OFF / R ON ratio and excellent endurance and retention. An electric conduction analysis indicated that the resistive switching behavior of the device was attributed to the trap controlled space-charge-limited current conduction that was caused by the oxygen vacancies in the PbTiO3 hydrothermal films. The modulation of the Pt/PbTiO3 Schottky-like junction depletion under an applied electric field is thought to be responsible for the resistive switching behavior of the device in the carrier injection-trapped/detrapped process.

The large number of energy levels available to lanthanide ions makes the emission mechanism of lanthanide-doped luminescent materials extremely complicated. Herein, we focus on the discussion and analysis of luminescence manipulation in Gd2O3:Yb3+/Er3+ nanocrystals and systematically investigate ion-ion interaction–induced energy transfer in up- and downconversion processes to shed light on the manipulation mechanism, showing that the luminescence of the above nanocrystals can be controlled by varying the content of Yb3+. Based on Dexter's energy transfer theory and the fact that excitation of Er3+ ions results in the appearance of emission attributed to the 2F5/2→2F7/2 transition of Yb3+ in the near-infrared region (950–1100 nm), this behavior is ascribed to the occurrence of energy transfer from Er3+ to Yb3+.

Tailoring the band gap and understanding the underlying mechanism are important for extending the applications of graphene quantum dots in optoelectronics. In this work, we synthesize fluorinated graphene oxide quantum dots (F-GOQDs) through a photochemical method, and study their optical properties. The obtained F-GOQDs exhibit a maximal blue-shift of photoluminescence (PL) emission of ca. 77 nm compared to that of the graphene oxide quantum dots (GOQDs). The PL shift results from the substitution of the hydroxyls and carbonyls groups with fluorine during the fluorination process, which can tune the band gap of the GOQDs. Density functional theory (DFT) calculations support our proposed mechanism for band gap tuning in the GOQDs through the use of fluorination.

Light-modulated lead-free perovskites-based memristors, combining photoresponse and memory, are promising as multifunctional devices. In this work, lead-free double perovskite Cs2AgBiBr6 films with dense surfaces and uniform grains were prepared by the low-temperature sol-gel method on indium tin oxide (ITO) substrates. A memory device based on a lead-free double perovskite Cs2AgBiBr6 film, Pt/Cs2AgBiBr6/ITO/glass, presents obvious bipolar resistive switching behavior. The ROFF/RON ratio under 445 nm wavelength light illumination is ~100 times greater than that in darkness. A long retention capability (&gt, 2400 s) and cycle-to-cycle consistency (&gt, 500 times) were observed in this device under light illumination. The resistive switching behavior is primarily attributed to the trap-controlled space-charge-limited current mechanism caused by bromine vacancies in the Cs2AgBiBr6 medium layer. Light modulates resistive states by regulating the condition of photo-generated carriers and changing the Schottky-like barrier of the Pt/Cs2AgBiBr6 interface under bias voltage sweeping.

High-quality CH3NH3PbI 3−xClx (MAPIC) films were prepared using potassium chloride (KCl) as an additive on indium tin oxide (ITO)-coated glass substrates using a simple one-step and low-temperature solution reaction. The Au/KCl-MAPIC/ITO/glass devices exhibited obvious multilevel resistive switching behavior, moderate endurance, and good retention performance. Electrical conduction analysis indicated that the resistive switching behavior of the KCl-doped MAPIC films was primarily attributed to the trap-controlled space-charge-limited current conduction that was caused by the iodine vacancies in the films. Moreover, the modulations of the barrier in the Au/KCl-MAPIC interface under bias voltages were thought to be responsible for the resistive switching in the carrier injection trapping/detrapping process.

Materials with tunable photoluminescence (PL) are highly desirable. It can lead to important applications such as photodetectors, bio-imaging, and broadband modulators. In this work, nitrogen-doped graphene oxide quantum dots (NGOQDs) were synthesized by hydrothermal method. The microstructures as well as optical properties of NGOQDs were studied. The as-prepared NGOQDs present tunable PL and exhibit a maximal PL blue-shift of ca. 88 nm compared to that of the graphene oxide quantum dots (GOQDs). The observed PL blue-shift of the NGOQDs is attributed to the high content of pyridine-like and pyrrolic-like nitrogen atoms doping in the NGOQDs. Our proposed mechanism for the PL blue-shift of the NGOQDs is supported by density functional theory (DFT) calculations.

Highly efficient H2 production from water splitting has been achieved by N-doped titanate nanotubes (N-TNTs) decorated with graphene quantum dots (GQDs) in this work. In order to promote charge carrier transmission at the interface, a facile and environmentally friendly in situ growth method was employed to construct a strongly coupled N-TNT/GQD composite photocatalyst. The results revealed that N atoms were effectively doped into the crystal lattice of the TNTs in the form of both interstitial N and substitutional N, and the GQDs were decorated onto both the inner and outer surfaces of the N-TNTs through the formation of Ti-O-C chemical bonds. Photoelectrochemical measurements proved that, in N-TNT/GQD composite, N-doping can extend light response to the visible-light range, and the coupling with GQDs not only enhanced visible-light absorption, but also promoted interfacial charge carrier transfer. Due to the synergistic effect between N-doping and GQD coupling, the closely integrated N-TNT/GQD composite exhibits a much superior photocatalytic H2 production performance under UV-vis irradiation, being 2.1 times higher than that of pure TNTs.