The investigation and understanding of heterointerfaces formation and charge transfer dynamics in two or more semiconductor heterojunctions increased ensuing establishment of S-scheme and dual S-scheme heterojunctions. However, investigations of possible charge transfer at interfaces and their type in four component systems are limited. Herein, a four-component heterojunction was investigated to postulate and demonstrate deviation between quadruple and triple S-scheme heterojunctions possibilities using LaNiO₃, BiOBr, CuBi₂O₄, and Bi₂WO₆. DFT and XPS were used to construct the band structure and support the charge transfer at the interfaces to follow S-S strategy during OTC and SMX degradation under visible light. IEF, bend bending systematically modulated charge transfer, and the core-shell strategy restricted possible junctions’ formation to three to accord triple S-scheme heterojunction. This work demonstrated the construction of Triple S-scheme heterostructures as a promising strategy for efficient charge separation making it a suitable candidate for elimination of pollutants.

Complications accompanying photocatalyst stability and recombination of exciton charges in pollutants degradation has been addressed through the construction of heterojunctions, especially S‐scheme heterojunction with strong and distinctive redox centres. Herein, an S‐scheme BiOBr (BOR) and g‐C₃N₄PO₄ (CNPO) catalyst (BORCNPO) with oxygen vacancy (Ov) was synthesized for levofloxacin (LVX) and oxytetracycline (OTC) photodegradation under visible light. The 3D/3D BORCNPO catalyst possessed C−O−Br bridging bonds for efficient charge transfer during the fabrication of S‐scheme heterojunction. In‐situ H₂O₂ formation affirmed by potassium titanium (IV) oxalate spectrophotometric method improved the mineralization ability of BORCNPO7.5 catalyst. Bi⁰ surface plasmon resonance (SPR) enhanced formation and involvement of ⋅O₂⁻ and the stability of the catalyst which increased reaction rate with increasing cycling experiments. XPS and radical trapping experiments supported the S‐scheme charge transfer mechanism formation with high degradation rate of LVX which was 3 times higher than OTC degradation rate. Mineralization of pollutants and their intermediates were demonstrated with florescence excitation and emission matrix (FEEM) and quadruple time of flight high performance liquid chromatography (QTOF‐HPLC). This work advances development of highly stable and efficient catalysts for photodegradation of pollutants through the formation of S‐scheme heterostructure.

Sulfate radicals based advanced oxidation processes (SR‐AOPs) have gained attention recently due to their high mineralization capability in environmental remediation. The high persulfate (PS) activation activity of cobalt‐based semiconductors has epitomized them as preferred catalysts for SR‐AOPs but shortcomings such as leaching, and loss of catalytic active sites limit their applicability. Herein, two different strategies are employed to minimize leaching and improve charge transportation and separation for efficient PS activation under visible light irradiation using LDH/CaCO ₃ /PS and Ba ₂ CoMnO ₅ /PS AOP systems synthesized by solid state method. LDH/CaCO ₃ /PS achieved 17.9% higher reaction rate than Ba ₂ CoMnO ₅ /PS for degradation of amoxicillin (AMX) with higher TOC mineralization efficacy. Despite SO ₄ ^•− and OH ^• existence and involvement in both systems, the degradation pathways mapped from QTOF‐HPLC‐MS data demonstrated formation of different pathways during AMX mineralization. This work demonstrates novel fabrication of brownmillerite double layered perovskite and insulator supported LDH for environmental pollution remediation.

Novel meso-tetra(4-carboxyphenyl)porphyrin tetramethyl ester metal derivatives were synthesised and characterized. These derivatives were interacted with graphene quantum dots (GDQs). Spectroscopic evidence that was obtained showed that the resultant conjugates were stable due to the strong π–π stacking interaction between the GQDs and the porphyrins. The fluorescence and singlet oxygen generating behaviour of the porphyrins and the nanoconjugates were investigated following incorporation. The dark toxicity and photodynamic therapy activities of the porphyrins and the nanoconjugates were successfully studied using MCF-7 breast cancer cells. Cell viability for the dark toxicity was more than 90% for all complexes. The PDT activities at the highest concentration of 120 μg ml⁻¹ showed a decrease in cell viability down to 15.2% for the GaClTMPP–GQDs.

Waterborne pathogens find their way into water bodies through contamination of fecal discharge, stormwater run-offs, agriculture and industrial activities, and poor water infrastructure. These organisms are responsible for causing diarrheal, gastroenteritis, cholera, and typhoid diseases which raise an alarming sense on public human health due to the high mortality rate, especially in children. Several studies have indicated that these waterborne diseases can be managed by monitoring pathogens in water using traditional culture-based and molecular techniques. However, these methods have shown several setbacks such as the longer duration for detection and the inability to detect pathogens at low concentrations. Effective management of these diseases requires rapid, sensitive, highly selective, fast, and efficient economic methods to monitor pathogens in water. Since the creation of biosensors, these tools have been applied and shown the ability to detect pathogens at low concentrations. The highlights of biosensor systems are that they are fast, portable, easy to use, highly sensitive, and specific. The capabilities of biosensors have given these tools exposure to be widely applied in detecting pharmaceutical pollutants, pesticides, toxins, residues of detergents, and cosmetics from household activities in soil and water. With such difficulties faced for detecting waterborne pathogens, this review evaluates the effectiveness of technologies for waterborne pathogens detection and their drawbacks. It further highlights biosensors as the current reliable method available for detecting pathogens in water and its future capabilities in sustaining safe potable water.