Journal of Materials Chemistry C最新文献

Perovskite (PVSK) materials have emerged as promising photo-responsive elements in memory devices due to their strong light absorption, simple structure, and non-contact optical programmability. In this study, pentacene was employed as the charge transport layer, MAPbBr₃ nanocrystals as the photoactive memory layer, and siloxane-based polyimides (PIs) as floating-gate dielectrics to modulate energy-level alignment and interfacial properties. Compared with polyamic acid (PAA), which is prone to hydrolysis and thermal degradation, PIs exhibit higher aromatic stability and defect passivation through imide groups, promoting stable PVSK crystal growth. Among the four PI variants, 6FDA-derived PIs contain bulky –CF₃ groups that interrupt conjugation, elevate HOMO energy levels, and increase the bandgap. Shorter siloxane segments further reduce surface energy and enhance interfacial contact, enabling optimal charge storage. The optimized 6FDA-1/PVSK device exhibited excellent photomemory performance under visible illumination (455–656 nm) at an ultralow operating voltage of −1 V, delivering an ON/OFF current ratio of ∼10⁴, a photocurrent ratio of ∼10⁵, stable cycling, and retention exceeding 10⁴ s. The ultralow operating voltage not only reduces power consumption but also offers potential advantages for biological and wearable applications, including enhanced safety, reduced thermal effects, and compatibility with flexible substrates. These results highlight that the low-voltage operation is a key advantage of this design. The findings indicate that molecular engineering of siloxane-based PIs not only stabilizes interfaces but also enables low-power, robust photomemory operation, offering potential for portable and flexible optoelectronic applications.

Liquid phase exfoliation of graphene is a sustainable and versatile approach for graphene processing. Mild solvents are commonly preferred for their lower toxicity, ease of handling, and environmental compatibility; however, they are not as effective at matching the surface energy of graphene, compromising exfoliation yield and stability. Here, we introduce phospholipids (PLs) to reduce the energy barrier for exfoliation owing to their amphiphilic nature. The PL-driven liquid phase exfoliation resulting in few-layer graphene (FLG) dispersions is investigated in organic (green) solvents of varying polarities to elucidate the effect of polarity on the resulting structures and dispersion. While previous studies have examined graphene exfoliation using green solvents, an understanding of how solvent polarity modulates surfactant behaviour, such as PLs conformation and its subsequent interaction with graphene, remains largely unexplored. The interaction between alcohols and PLs regulates their fluidity, conformation, orientation, and species formations. These properties emerge as key experimental parameters leading to enhanced dispersibility, higher exfoliation yield, and distinct lipid fingerprints on the graphene surface. Among the tested solvents, ethanol provided superior graphene dispersibility and stability over an extended period compared to methanol and isopropanol. As proof of concept, the resulting dispersion was used as a conducting ink to coat a hydrogel-based adhesive, highlighting its excellent film-forming properties and wettability, and was used to record electrocardiogram signals from the skin surface. Our findings reveal that alcohol interactions can modify PL properties, and highlights that the bare surface of nanomaterials, such as graphene, can trigger the formation of a slowly exchanging interfacial molecular layer. This process depends on the physiochemical state of the biomolecule in the surrounding medium and provides new insights into controlling interfacial behavior for targeted applications. This work establishes a framework for employing environmentally friendly solvents and biomolecules in graphene exfoliation, offering a versatile platform for the direct integration of biomimetic structures and biomolecules onto 2D materials.

Thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs) offer high external quantum efficiencies without rare metals, but efficient orange–red emitters remain limited due to difficulty in achieving high photoluminescence quantum yields (PLQYs) at longer wavelengths. In this study, we report the design, synthesis, and comprehensive characterization of three novel donor–π–acceptor (D–π–A) TADF emitters Cz-PhQx4CN, Ac-PhQx4CN, and PXZ-PhQx4CN based on a cyanophenyl-substituted quinoxaline acceptor unit. Strategic donor modulation and cyano-functionalized quinoxaline acceptor design enabled broad range orange-to-deep red emission (603–700 nm) by enhancing intramolecular charge transfer and minimizing the singlet–triplet energy gap (ΔE_ST). Photophysical, electrochemical, and theoretical studies confirmed strong ICT character and efficient RISC across the series. Cz-PhQx4CN showed pronounced AIE, a high PLQY (37.8%), a small ΔE_ST (34 meV), and the best device performance with an EQE of 9.9% in vacuum-deposited and 3.6% in solution-processed OLEDs. PXZ-PhQx4CN and Ac-PhQx4CN also exhibited TADF behaviour with red-shifted emissions but lower efficiencies. These results highlight how molecular rigidity, extended conjugation, and careful donor–acceptor design enable efficient long-wavelength TADF emission, offering valuable guidance for developing high-performance orange–red OLEDs.

Phthalocyanines and subphthalocyanines have emerged as highly adaptable molecular platforms with diverse applications, predominantly due to their tunable photophysical properties achieved through the variation in axial and peripheral substituents and central metal atoms. Despite these benefits, their broader application has been hindered by their intrinsic hydrophobicity and strong aggregation in aqueous environments, leading to aggregation-caused quenching (ACQ) and poor photoluminescence performance. Recent advances have demonstrated that integrating aggregation-induced emission luminogens (AIEgens), such as tetraphenylethene and triphenylamine, into phthalocyanine and subphthalocyanine frameworks can efficiently overcome ACQ. This strategy restricts intramolecular motions, converting traditional ACQ-type systems into AIE-active materials with significantly improved emission. Moreover, the unique cone-shaped, π-conjugated architecture of subphthalocyanines enables efficient fluorescence resonance energy transfer when combined with AIE-active groups, further enhancing their photophysical properties. In this perspective, we highlight the recent progress in the development of AIEgen-integrated phthalocyanines and subphthalocyanines, discuss their structure–activity relationships, and explore their potential for advanced applications. To our knowledge, this is the first review to focus on the growing importance and future opportunities of integrating AIEgens with phthalocyanine and subphthalocyanine systems.

Two-dimensional MXene materials have demonstrated significant potential in the field of nonlinear optics. However, their environmental stability remains a challenge, limiting their practical applications. In this study, a fluoride-free etching strategy is proposed for the synthesis of ultrastable partially etched Ti₃AlC₂. A tunable transition from nonlinear scattering (NLS) to saturable absorption (SA) is achieved via ultrasonic-assisted particle size regulation. This transformation is attributed to the enhanced heat dissipation capacity of the samples resulting from the increase in the specific surface area. Z-scan measurements reveal that the sample (S-Ti₃Al_1−xC₂) obtained after 60 minutes of ultrasonication exhibits pronounced saturable absorption under 532 nm laser excitation, with a nonlinear absorption coefficient of −2.4844 cm GW⁻¹ and a modulation depth of 29.57%, comparable to that of fully etched Ti₃C₂T_x. In addition, the presence of residual aluminum atoms endows the material with excellent oxidation resistance. After undergoing a high-temperature aging process at 80 °C for 30 hours, S-Ti₃Al_1−xC₂ retained over 85% of their initial saturable absorption properties. Furthermore, no TiO₂ peaks were observed in the XRD pattern, indicating minimal oxidation. These findings demonstrate a safe and effective preparation method for the synthesis of highly stable nonlinear optical materials.

Rhodamine B (RhB) is a dye extensively used in the textile industry; however, it poses significant environmental challenges due to its high stability in aquatic environments. To address this issue, we have successfully synthesized a water-stable organic–inorganic hybrid perovskite material [(4,4′-VDP)Pb₂Br₆] and applied it for the first time for the photocatalytic degradation of RhB in aqueous solutions. Results demonstrate that (4,4′-VDP)Pb₂Br₆ is a highly efficient photocatalyst, which achieved over 96% degradation of RhB within 60 minutes of illumination and nearly complete degradation after an extended irradiation for 100 minutes, following reaction kinetics consistent with a pseudo-first-order model. Moreover, the material retained a stable photocatalytic activity over five consecutive cycles without significant loss in its performance, highlighting its excellent reusability and stability. The unchanged X-ray diffraction (XRD) patterns before and after the photocatalytic reaction confirm the exceptional structural stability of (4,4′-VDP)Pb₂Br₆ and further validate its outstanding water stability. These findings indicate that the as-prepared (4,4′-VDP)Pb₂Br₆ material holds great promise for practical applications owing to its high degradation efficiency and remarkable stability in aqueous environments.

Programmable devices exhibit inherent advantages in communication systems, low-power multi-logic operations, and intelligent optical sensing applications, making them ideal candidates for optoelectronic integrated circuits. This study demonstrates a local gate photodetector based on a WSe₂/h-BN/Gr heterostructure. Through the synergistic modulation of gate voltages and optical signals, the device achieves reconfigurable logic operations, optical communication, and image recognition functionalities within a single architecture. The fabricated device exhibits remarkable performance metrics, including an ultrahigh switching ratio of 8 × 10⁵ and a fast response time of 0.33 ms, ensuring reliable logic gate switching in photovoltaic mode. Gate-voltage modulation enables the dynamic configuration of n⁺–n and p–n junctions, with reversible switching between positive and negative photoresponses under illumination. Furthermore, the linear dependence of photocurrent on both light intensity and gate voltage facilitates the implementation of convolutional neural networks for broadband image recognition and classification.

Charge-transfer transitions constitute a pivotal mechanism for modulating the photophysical characteristics in organic luminescent materials. Intermolecular charge transfer transitions offer flexibility for designing organic light-emitting materials beyond the single-molecule level. However, the lower-lying triplet excited states in such systems usually remain in the dark state and decay either through reverse intersystem crossing, triplet–triplet energy transfer or nonradiative transitions. Activating the emission from the lowest triplet intermolecular charge-transfer excited states unlocks new possibilities for advancing organic optoelectronics. In this study, we demonstrate a crystal engineering strategy by incorporating a multi-resonance organic molecule, 9H-quinolino[3,2,1-kl]phenothiazin-9-one (QPO), into a crystal matrix of a phosphorescent iridium complex, bis(2-phenylpyridine)(acetylacetonate)iridium (Ir(ppy)₂(acac)). The crystalline lattice enables tighter binding between QPO and Ir(ppy)₂(acac) molecules, facilitating strong intermolecular charge transfer interactions. The doped crystal exhibits a remarkable 135 nm bathochromic shift in emission compared to its individual components and amorphous counterpart. Through detailed experimental and theoretical characterization of the crystal, we attributed the emission to phosphorescence from the lowest intermolecular charge-transfer state with a triplet character. The proposed crystal design approach can be applied to a broad class of materials, opening new opportunities for improving the performance of optoelectronic devices.

Ferroelectric phases in Hf_0.5Zr_0.5O₂ (HZO) films are stabilized by an appropriate concentration of oxygen vacancies, but an artificial heterostructure that controls oxygen vacancies at the interface needs to be developed to balance the beneficial and detrimental effects of oxygen vacancies. Here, we demonstrate that inserting oxygen-diffusive V₂O₅ interlayers at the electrode/HZO interface increases remnant polarization (P_r) and decreases coercive field (V_c), as well as improves the device reliability of HZO ferroelectric devices further. Interestingly, the fully woken-up V₂O₅ (6 nm)/HZO (9 nm) stack exhibited a maximum 2P_r of 77.07 µC cm⁻² from hysteresis loops and 64.42 µC cm⁻² from PUND, whose values are 48.27% and 41.99% higher than those of HZO without V₂O₅, respectively. Moreover, V₂O₅/HZO showed an excellent device-to-device variation of 2P_r with a standard deviation of 1.10 µC cm⁻². Atomic-scale characterization combined with synchrotron X-ray diffraction confirms that V₂O₅-triggered oxygen redistribution during wakeup cycles is likely to facilitate the conversion and alignment of the ferroelectric domain of HZO; our study will provide a new strategy of interface engineering between electrodes and ferroelectrics to further enhance remnant polarization and decrease the coercive field in hafnium-based ferroelectrics for emerging applications.

In inkjet printing, ink formulation is the foundation to get stable droplets and films with high uniformity. Typically, inks for printing are composed of binary solvents consisting of the main solvent and a co-solvent, where the main solvent provides solubility for the luminescent materials and the co-solvent adjusts the physical parameters of the ink to optimize the ink's printability and film-uniformity properties. However, the principles of main solvent selection are not the same for small molecules and polymers. In this work, we propose the selection criterion of main solvents for small molecules and polymers from three aspects: solvent solubility, film-forming ability, and droplet behavior. The dendrimer Ir(Ph-BM-P2D2)₃ (G2P2) and the polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) were used to compare the differences in solvent selection between small-molecule and polymer inks. Polymer F8BT is poorly soluble but has good film-forming ability. Toluene (TOL), with low viscosity and surface tension, meets dissolution requirements and film-forming integrity. Small molecule G2P2 has many good solvents; however, cyclohexanone (CYC) as the main solvent has not only good solubility but also a high boiling point (155 °C), viscosity (2.2 mPa s) and low surface tension (32.5 mN m⁻¹), ensuring that the film dries slowly without de-wetting. The role of co-solvents for polymers and dendrimers is the same: to eliminate satellite droplets and coffee-ring effects. Cyclohexylbenzene (CHB), with a high viscosity (2.7 mPa s) and a high boiling point (237 °C), was used as a co-solvent. The parameter ranges for printhead suitability were 23.20 < Z < 68.05 for F8BT and 14.87 < Z < 21.17 for G2P2. Finally, the F8BT binary solvent is TOL/CHB = 5/5 and the G2P2 binary solvent is CYC/CHB = 5/5, which inhibits the generation of long trailing and satellite droplets in ink printing and the de-wetting and coffee-ring effects in the film-forming process.