Shoaib Anwer

Integrated optoelectronic synapses that combine sensing, memory, and computation in a mechanically compliant platform are attractive for energy‐efficient wearable artificial vision and in‐sensor computing. However, simultaneously achieving intrinsic rectification, analog weight programmability, optical responsivity, and facile, scalable fabrication remains challenging. Here, we report a self‐rectifying, flexible, semi‐transparent optoelectronic memristor fabricated by layer‐by‐layer solution processing and spray coating, thereby avoiding the use of vacuum‐deposited noble‐metal top electrodes. The indium tin oxide/ZnO/TiO ₂ nanosheet/MXene heterostructure uses defect‐rich ZnO as a photoactive oxygen‐vacancy reservoir, crystalline TiO ₂ nanosheets (TS) as a charge‐trapping and barrier‐modulating interlayer, and a termination‐rich 2D MXene sheets (MS) electrode to promote asymmetric carrier injection. The device exhibits unidirectional analog switching with a rectification ratio of ~10 ³ , stable potentiation and depression with nonlinearity values of 2.02 and 2.38, a conductance on/off ratio of 121.4, and 94.3% inference accuracy using experimentally extracted weight states. Under illumination, it shows wavelength‐selective photosynaptic behavior, stronger excitation at 365 nm, along with intensity‐ and duration‐dependent transitions from short‐term plasticity (STP) to long‐term plasticity (LTP), paired‐pulse facilitation (PPF), and learning‐forgetting‐relearning characteristics. These electrical and optoelectronic functions are preserved under bending, supporting robust mechanical reliability. Mechanistically, the response is governed by interface‐controlled barrier modulation mediated by oxygen‐vacancy redistribution, charge trapping/de‐trapping at the ZnO/TS interface, and asymmetric carrier injection at the MS/TS contact, as evidenced by postsynaptic current (PSC). This work establishes a scalable, semi‐transparent platform for energy‐efficient neuromorphic photosensing and in‐sensor wearable computing for artificial vision systems.

Achieving stable dispersion of graphite flakes (GFs) in aqueous media remains a critical challenge in developing high‐performance graphite flake nanofluids (GNFs) for direct photothermal energy harvesting. This study explored the synergistic effects of anionic and nonionic surfactants on colloidal stability, optical properties, and photothermal response of GNFs. Among all the engineered formulations, the mixed‐surfactant system containing 20 wt.% Tween 80 (T80, nonionic) and 80 wt.% sodium dodecyl sulfate (SDS, anionic), (GNF@T80 ₂₀ %–SDS ₈₀ %) exhibited the highest dispersion stability with improved photothermal performance, maintaining uniform suspension for over 40 days. UV–Vis spectroscopy showed a distinct redshift in the π → π* transition, attributed to improved exfoliation and enhanced interfacial polarizability from the dual surfactant system, which stabilized the excited electronic states at lower energies. This optimized formulation achieved photothermal conversion efficiency of 91% under AM 1.5G solar irradiation, outperforming both single‐surfactant and base fluid counterparts. Numerical simulations using a morphology‐corrected Mie scattering model closely matched the experimental extinction spectra, validating the optical behavior. Radiative transfer analysis further confirmed ~93% total solar absorption before 3 cm depth. This work establishes a synergistic surfactant‐assisted design and modeling strategy for producing stable, high‐efficiency GNFs, paving the way for their application in next‐generation solar thermal energy conversion systems.

Two‐dimensional nanoparticle‐enhanced phase change materials are transforming thermal management by improving thermal conductivity and heat transfer efficiency, offering efficient and sustainable cooling solutions than conventional hydrocarbon‐based phase change materials. However, the environmental concerns necessitate the development of eco‐friendly and green alternatives. This study presents a green alternative by developing two‐dimensional nanoparticle‐enhanced phase change materials using biodegradable beeswax infused with reduced graphene oxide, graphene oxide, and Ti ₃ C ₂ T _x MXene nanoparticles at varying concentrations (0.1–0.5 wt.%), a sustainable and eco‐friendly alternative to paraffin wax. Comprehensive material characterization confirmed the structural stability and chemical compatibility of the prepared composites. Experimental results demonstrated that the addition of nanoparticles increased the thermal conductivity by 21.9% (up to 0.278 W (m·K) ⁻¹ ) while maintaining latent heat storage capacity within 6–18% of the base phase change materials values. Experimental findings of thermophysical properties, including thermal conductivity and viscosity, were used to train machine learning based regression models, yielding predictive accuracy levels up to 95%. Additionally, numerical simulations based on these models replicated the experimental results, providing a reliable framework for future predictions. A discontinuity estimation model was also developed to accurately predict thermal conductivity changes during phase transitions, achieving 98% accuracy compared with experimental data. Computational simulations validated against experimental data showed a strong correlation (3 C ₂ T _x MXene, supporting its potential as a sustainable, biodegradable alternative. This integrated experimental‐numerical approach supports the development of high‐performance, eco‐friendly nanoparticle‐enhanced phase change materials, advancing sustainable thermal management solutions for next‐generation cooling applications.

Solar energy harvesting using photothermal nanofluids (NFs) depends greatly on how well light interacts with the suspended particles and how stable those particles remain in the base fluid. This work presents a geometrically engineered hierarchical design of hollow‐core copper sulfide (H‐Cu ₂ S) nanostructures (NSs) dispersed in ethylene glycol (EG) to enhance photothermal performance. The tailored shell morphology with hollow‐core facilitates multiple light scattering and extended photon trapping, significantly enhancing solar absorption, particularly in the near‐infrared region. This morphology‐driven approach addresses limitations of conventional polymer or surfactant coatings, which, while improving colloidal stability, often compromise light accessibility and thermal conversion efficiency. The synthesized H‐Cu ₂ S/EG NF demonstrated exceptional colloidal stability, negligible sedimentation, low viscosity enhancement, and robust thermal cycling, even at ultra‐low loading of 0.01 wt%. Compared to 2D Cu ₂ S counterparts, this enhanced photon trapping, combined with the material's intrinsic semiconductor properties, yields an exceptional photothermal conversion efficiency of 86.8%, representing a 64.72% increase over EG as the base fluid. These features are achieved without the need for surface modification, benefiting from the intrinsically low density and optimized geometry of the NS. The resulting NFs exhibit significantly enhanced solar absorption and efficient light‐to‐heat conversion, establishing H‐Cu ₂ S/EG NFs as promising candidates for next‐generation solar thermal technologies. image

The world is striving to design renewable energy systems to reduce reliance on finite fossil fuels and minimize environmental impacts. Photothermal nanofluids (NFs) in solar energy harvesting center on achieving a delicate balance between effective solar absorption, light-to-heat thermal conversion, dispersion stability, and viscosity. This study focuses on the formulation of high-performance stable NFs by incorporating different mass fractions of sodium ascorbate-treated ultrathin 2-dimensional (2D) Ti ₃ C ₂ T _x MXene nanosheets (SA-TMS) in ethylene glycol (EG) base fluid. Optical and photothermal characterization of the NF, including dispersion, suspension stability, viscosity, and photothermal conversion, were thoroughly examined for the prepared series. Interestingly, compared to pure EG, adding 0.0018 wt % of SA-TMS improved the photothermal performance of EG by 68.73%, credited to the large extinction coefficient of 64.4 l/(g·cm) and localized surface plasmon resonance effect of high conductive ultrathin SA-TMS nanosheets. Furthermore, the optimized SA-TMS/EG ^o NF was semitransparent with a minimum effective viscosity of 18.88 mPa·s because of its exceptional self-lubricating properties. In addition to having a good cycling life, the recruited SA-TMS/EG NFs showed no signs of sedimentation after 90 d and showed promising shelf stability. Furthermore, the photothermal conversion performance study proved that large-size 2D sheets are more efficient than smaller-size sheets. This comprehensive study opens an exciting regime to design stable and efficient 2D material-based NFs for direct solar energy harvesting, leveraging their enhanced thermal conductivity and optically semitransparent nature.