Colloidal Quantum Dots as an Emerging Vast Platform and Versatile Sensitizer for Singlet Molecular Oxygen Generation

Singlet molecular oxygen (¹O₂) has been reported in wide arrays of applications ranging from optoelectronic to photooxygenation reactions and therapy in biomedical proposals. It is also considered a major determinant of photodynamic therapy (PDT) efficacy. Since the direct excitation from the triplet ground state (³O₂) of oxygen to the singlet excited state ¹O₂ is spin forbidden; therefore, a rational design and development of heterogeneous sensitizers is remarkably important for the efficient production of ¹O₂. For this purpose, quantum dots (QDs) have emerged as versatile candidates either by acting individually as sensitizers for ¹O₂ generation or by working in conjunction with other inorganic materials or organic sensitizers by providing them a vast platform. Thus, conjoining the photophysical properties of QDs with other materials, e.g., coupling/combining with other inorganic materials, doping with the transition metal ions or lanthanide ions, and conjugation with a molecular sensitizer provide the opportunity to achieve high-efficiency quantum yields of ¹O₂ which is not possible with either component separately. Hence, the current review has been focused on the recent advances made in the semiconductor QDs, perovskite QDs, and transition metal dichalcogenide QD-sensitized ¹O₂ generation in the context of ongoing and previously published research work (over the past eight years, from 2015 to 2023).