The discharge of synthetic dyes from the textile industry poses a pressing environmental problem requiring sustainable and efficient photocatalytic treatment. In this work, CaO/activated carbon nanocomposites (CaO/AC NCs) were synthesized by thermal treatment of biowaste, namely eggshells and rice husks, without the use of chemical additives. Comprehensive physicochemical characterizations using FE-SEM, EDX, FTIR, and XRD confirmed the formation of a well-integrated CaO/AC heterointerface with improved surface area and crystallinity. The synthesized nanocomposite (CaO/AC3) exhibited the best architecture for visible-induced photocatalysis at 900°C, with rapid degradation rates of 99.8% for methylene blue (MB, 120 min) and 98.4% for methyl orange (MO, 130 min). Surprisingly, an equimolar mixture of MB and MO was completely degraded within 90 min, indicating optimal charge transport at the interface and strong redox synergy. Kinetic analyses revealed that the photocatalysis follows zero-order kinetics, suggesting dye-independent photocatalytic activity. Mechanistic investigations showed that CaO/AC3 operates via an S-scheme charge transfer mechanism, enabling effective electron-hole separation and maintaining a high redox potential in visible light. Overall, the developed catalyst can therefore be used as an efficient and effective photocatalyst, killing two birds with one stone. Remarkably, the calculated quantum yield of waste-derived CaO/AC3 (4.948 × 10−6 (MB) and 4.734 × 10−4 (MO)) is significantly higher than that of other reported chemically synthesized photocatalysts (e.g., rGO/TiO2, Ni-doped/TiO2, and Cds/CoFe2O4). Moreover, CaO/AC3 exhibited remarkable stability with an efficiency exceeding 95% over five consecutive cycles. This work not only elucidates the relationship between the structure and properties of the S-scheme in the charge migration of biowaste heterostructures but also establishes a scalable, environmentally friendly approach for finely tuned, second-generation photocatalysts for the purification of industrial wastewater.
Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized via a green plasma–liquid interaction approach and evaluated as fluorescent probes for Cu2+ detection. The N-CQDs exhibited excitation-dependent photoluminescence and efficient fluorescence quenching upon the addition of Cu2+. Stern–Volmer analysis showed a linear response over 0–6 nM, with a quenching constant of 0.8505 nM⁻1 and a detection limit of 2.3 nM. Time-resolved photoluminescence revealed enhanced non-radiative relaxation, while deviation from Stern–Volmer linearity at higher concentrations indicated the coexistence of dynamic and static quenching. DFT and TD-DFT calculations showed that Cu2+ adsorption redistributed the frontier molecular orbitals, with the HOMO delocalized over the π-conjugated framework and the LUMO localized near the Cu²⁺ adsorption site, supporting an orbital-mediated π→Cu2+ charge-transfer mechanism. These findings demonstrate that defect-induced electronic-structure modulation, rather than conventional coordination alone, governs fluorescence quenching and provides a framework for designing carbon-based fluorescent sensors.
Improving the performance of DSSCs relies on engineering photoanodes that can efficiently harvest photons, promote dye adsorption and inhibit recombination of charges. To address these challenges, DSSCs using Cu:Nb2O5 films as photoanode have been fabricated and their photovoltaic performance was investigated. XRD confirmed the retention of orthorhombic Nb2O5 with lattice distortion arising from Cu doping. Morphological examination revealed nanopore formation and increased particle size upon doping. Contact angle and AFM results showed that Cu doping promoted hydrophilicity and surface roughness that favours dye loading and electrolyte penetration. PL quenching upon Cu doping confirmed effective suppression of charge carrier pair recombination. The outcomes reveal that 5 wt% Cu:Nb2O5 photoanode based DSSC exhibited the best PCE of 8.82% with longer electron lifetime (16.61 ms) and reduced recombination resistance (21.06 Ω) compared to the pristine system 7.05%. Thus, Cu doping boosts its photovoltaic function, positioning Cu:Nb2O5 as workable photoanode for high performance DSSCs.
The uncontrolled release of dyes and pathogens from textile effluents demands multifunctional materials for water remediation. In this study, TiO2 and 1%, 3%, and 5% Ce-doped TiO2 nanoparticles were synthesised via a Sol-Gel method. Structural and elemental analyses confirmed anatase-phase nanoparticles with successful Ce incorporation, mixed Ce3+/Ce4+ states, and oxygen-vacancy formation. Ce doping reduced the band gap from 3.11 eV (TiO2) to 2.92 eV (3% Ce-TiO2), accompanied by pronounced photoluminescence quenching. Among the synthesized samples, 3% Ce-TiO2 demonstrated superior photocatalytic performance. The catalyst efficiently degraded various cationic and anionic dyes, as well as real textile wastewater, achieving degradation efficiencies of 97% under UV irradiation and 94% under sunlight, while retaining its stability over five cycles. Treated wastewater showed reduced toxicity in Vigna radiata seed germination assays. The material also demonstrated antibacterial activity against Staphylococcus aureus and Escherichia coli, highlighting its potential for sustainable textile wastewater treatment.
High-performance optical thermometers operating in the second near-infrared (NIR-II) window hold great promise for biomedical applications due to their tissue penetration depth and minimal autofluorescence. However, developing reliable NIR-II thermometers with high sensitivity and robust performance across a wide temperature range remains a challenge. Herein, the luminescence properties and NIR-II ratiometric thermometric performance of Er3+, Ho3+, Yb3+ co-doped Bi4Ti3O12 (BTO) perovskite oxide were investigated. Upon 980 nm excitation, NIR-II emission from Er3+ at 1560 nm (4I13/2 → 4I15/2) and Ho3+ at 1200 nm (5I6 → 5I8) was achieved. A ratiometric thermometer was constructed using the temperature-dependent intensity ratio, IEr/IHo. Relying on the thermal dependence of this ratio, the BTO system exhibits a relative sensitivity (Sr) of 1.3% at 333 K. Furthermore, the results suggest that phonon characteristics of the BTO host influence energy-transfer processes and NIR-II thermometric performance, highlighting importance of host properties in designing rare-earth-doped NIR-II thermometric materials.
The development of efficient photocatalysts for water purification remains challenged by rapid charge recombination and limited surface reactivity. Here, we report a rationally designed PHI/W₁₈O₄₉ heterojunction photocatalyst, integrating interfacial W–N bonds and oxygen vacancies to synergistically overcome these limitations. The optimized PHI/W₁₈O₄₉ heterojunction exhibits significantly enhanced visible-light absorption, efficient spatial charge separation, and improved surface reaction kinetics. Consequently, it demonstrates superior and versatile photocatalytic performance in degrading organic contaminants, along with stable recyclability and consistent performance in real water matrices, highlighting its potential for practical applications. Mechanistic studies combining DFT calculations and experimental characterization reveal that interfacial W–N bonds direct S-scheme electron transfer, while oxygen vacancies enhance reactant adsorption, jointly boosting charge separation and surface reactivity. This work establishes a design paradigm that couples’ defect-enhanced surface adsorption with directed interfacial electron flow, offering an effective strategy for developing robust photocatalysts for practical environmental remediation.
We report the temperature-dependent photoluminescence properties of 2-thenoyltrifluoroacetone (TTFA)-sensitised NaMgF3:Eu (0.1 mol% to 5 mol%) nanoparticles. Maximum sensitisation was observed for 1%Eu doping, and the sensitised emissions were dominated by highly distorted Eu3+ ions in the nanoparticle shell region. All Eu3+ emissions decreased as the temperature increased from 300 K to 460 K. This thermal quenching is well described by a kinetic model featuring thermally-induced back transfer from the Eu3+ 5D0 state to the TTFA T1 triplet state prior to non-radiative decay. The model places the T1 state 0.44 eV above the 5D0 state and 0.21 eV above the Eu3+ 5D1 state in TTFA-sensitised NaMgF3:Eu. The ratio of the magnetic dipole (5D0 → 7F1) and forced electric dipole (5D0 → 7F2) emission intensities was also temperature dependent. Thus, TTFA-sensitised NaMgF3:Eu nanoparticles have potential for both intensity-based and ratiometric photoluminescent nanothermometry with relative sensitivities up to 2.7%/K.
ZnS/ZnO heterojunctions were fabricated by controlled calcination of commercial ZnS powder. The phase evolution, microstructure, and n-butanol sensing properties were systematically correlated to identify the role of oxidation degree in regulating sensing behavior. The sample calcined at 550 °C for 7 h exhibited a porous coral-like architecture with in situ formed ZnS/ZnO interfaces and showed the best sensing performance. At 260 °C, the response to 100 ppm n-butanol reached 42.9, which was 2.5 and 3.8 times higher than those of pure ZnS and ZnO, respectively. The sensor exhibited relatively rapid response and recovery, good repeatability, and distinguishable response signals at 0.2 ppm n-butanol, which was the minimum tested concentration in this study, with a statistically estimated LOD of approximately 0.15 ppm. The improved sensing behavior was mainly associated with the cooperative contribution of interfacial charge modulation at the ZnS/ZnO heterointerface and the preserved porous structure.
With the emergence of two-dimensional (2D) black phosphorus (BP), there has been a resurgence of interest in black phosphorus within scientific and technological circles. Consequently, numerous investigations of this recent component of the 2D realm have emerged. This review presents current advancements, structural characteristics, and synthesis methods of black phosphorus. The discussion comprehensively addresses anisotropies in mechanical properties, thermal conductivity, carrier transport, and optical properties. In this review, essential characteristics of BP photocatalysts, such as their crystal structure, band-gap and electronic structures, charge mobility and electrical conductivity, material stability, mechanical and thermal properties, are briefly described. Synthesis techniques, modifications, morphology control of 2D black phosphorus and their application in energy harvesting through photocatalysis, energy storage, environmental pollutant treatment, solar-driven nitrogen fixation, and disinfection have been discussed. It also identifies challenges faced by the community and provides a forward-looking perspective on next-generation 2D black phosphorus, emphasising its potential for energy production.
