Quantum dots (QDs) are semiconductor nanocrystals (NCs) with excellent optical and electronic properties arising from strong exciton confinement. Their biomedical and technological potential have significantly contributed to nanotechnology. The QD field has evolved from traditional toxic heavy metal-based elements, such as Cd, Pb, Hg, chalcogens, and halogens, to a new focus on less-toxic alternatives from I-VI, III-V, and I-III-VI groups. Despite their attractive optical properties, the toxicity of conventional QDs limits their biomedical and clinical prospects. Recently, safer QDs based on chalcogenides of In, Ag, Ga, and Cu have been developed, offering absorption and emission in the biological I and II windows. Advances in synthesis, shell preparation, ligand exchange, and bioconjugation have further tailored these QDs for stable and specific applications, including targeted multimodal bioimaging, drug delivery, phototherapy, and image-guided therapy with high spatial, spectral, and temporal resolutions. This review highlights the transition from classical cadmium-, lead-, and mercury-based QDs to less-toxic silver-, copper-, and indium-based QDs for bioimaging and photodynamic therapy (PDT). First, we touch on classical developments in the synthesis, optical properties, and biological applications of heavy metals (Cd/Pb/Hg)-based QDs, before focusing the major parts on the synthesis, optical properties, bioconjugation, and bioimaging aspects of core only and core-shell nanomaterials from I-VI (Ag2S, Ag2Se, and Ag2Te), III-V (GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb), and I-III-VI (CuInS2, CuInSe2, CuInTe2, CuGaS2, CuGaSe2, AgGaS2, AgGaSe2, AgInS2, AgInSe2, and AgInTe2) groups. The discussion proceeds to the PDT potential of QDs, a minimally invasive method for treating cancers and infections that uses lightactivated PSs to generate ROS, such as singlet oxygen (1O2) and superoxide (O2 center dot-). We emphasize the importance of these nanomaterials over traditional organic PSs, such as porphyrins and phthalocyanines, which suffer from poor stability, narrow-band light absorption, and limited tissue penetration. Conversely, QDs offer broad and NIR light absorption, high photostability, and tunable surfaces for bioconjugation and targeted, imageguided therapy. The review highlights the mechanism and applications of III-V and I-III-VI QDs in tumor and infection treatment, while addressing challenges such as toxicity, hypoxia tolerance, and clinical translation toward multifunctional theragnostic systems, highlighting the pathway for safer, more versatile tools in clinical testing, imaging, and therapy, driving future innovations in healthcare.
Sunlight-driven photocatalysis offers a promising approach to simultaneously and sustainably address environmental pollution and energy challenges. Among the various photocatalysts, TiO2 nanotube arrays (TNTAs) have gained prominence owing to their distinctive structural configuration, large surface area, rapid electron transport, and adjustable morphology. However, owing to the intrinsic bandgap limitations of TiO2, modifications are required to enhance its photocatalytic efficiency. This review article provides a comprehensive overview of the formation of TNTAs on various substrates and explores their modification for applications in photo-electrochemical (PEC) water splitting and environmental remediation. The mechanisms of photocatalysis and PEC reactions, along with strategies for electronic structure engineering are discussed. The manuscript systematically evaluates the primary synthesis approaches for TNTAs, including electrochemical anodization, hydrothermal, sol-gel, and template-assisted methods. Recent developments in the growth of TNTAs on different substrates are presented, covering pristine titanium and modified TNTAs incorporating metals, metal oxides, semiconductors, and carbon materials as well as Ti-based binary alloys and other substrates. In addition, recent applications in water splitting and environmental remediation consisting of the degradation of organic dyes, the photoreduction of heavy metal ions, and the elimination of gaseous pollutants on these TNTA-based substrates are comprehensively described. Research gaps are discussed, and the challenges and prospects for the use of TNTAs are highlighted. This review aims to provide insights toward a better understanding of TNTA-based composites and their future applications as efficient photocatalysts.
The global cancer burden continues to rise, underscoring an urgent need for therapeutic approaches that are both safe and precisely targeted. Photodynamic therapy (PDT) has gained increasing attention in precision oncology owing to its high selectivity, minimal systemic toxicity, spatiotemporal control, and effectiveness against tumors exhibiting multidrug resistance. Its mechanism centers on photosensitizers (PSs) that generate reactive oxygen species (ROS) upon light exposure to trigger tumor cell death. These processes are broadly categorized into two types: Type I, which operates through electron transfer to yield radical species with low oxygen dependence, and Type II, which primarily produces singlet oxygen (1O2) in a manner strictly reliant on molecular oxygen. The latter is significantly constrained in hypoxic tumor microenvironments, whereas Type I pathways remain functional under such conditions. This article reviews the design strategies and latest progress of the transition from type II to type I PSs in recent years, including structural modification of small molecule photosensitizers and functional construction strategies based on nanocarriers and supramolecular assembly. And their application in photodynamic therapy aims to promote the development of new PDT systems suitable for hypoxic tumor environments, and explores the current challenges and future development directions.
Hydrogen peroxide (H2O2), an environmentally friendly and highly efficient oxidant, is widely utilized in fields including medicine, energy, and environmental engineering. Compared with the conventional anthraquinone process, photocatalytic H2O2 production is recognized as a highly promising technical route, attributed to its safety, green properties, and low cost. Moreover, donor-acceptor (D-A) type organic pi-conjugated polymers (CPs) constructed from D-A units have emerged as highly potential photocatalysts in this field, owing to their excellent light absorption performance, precisely tunable molecular structures, and high charge carrier separation rates. Herein, we systematically review the latest research progress and modification strategies of D-A type CPs for photocatalytic H2O2 production. First, we briefly introduce the fundamental principles of photocatalysis and the formation pathways of H2O2, while simultaneously outlining the typical characteristics of intramolecular and intermolecular D-A structures. Subsequently, we systematically summarize the construction approaches of D-A type CPs, with a particular focus on elaborating the synergistic modification strategies that integrate structural regulation with morphological optimization/functionalization. Finally, this review outlines the future development directions and potential challenges of D-A type CPs in solar-driven H2O2 production. It aims to provide a comprehensive and novel reference for the precise molecular-level design and performance optimization of D-A type photocatalysts, which is expected to facilitate the advancement of D-A type CPs in the field of photocatalysis.
Stenhouse compounds were first described in the 19th century but have recently received renewed interest due to their novel light-responsive chemistry, particularly the formation of cyclic intermediates known as Stenhouse photoadducts. The photochromic reversible switching of these compounds is central to the formation of photoadducts during the light-induced rearrangement of open-chain Stenhouse intermediates. When formed, they alter the optical properties of the molecules and modify their thermal stability, fatigue properties, and capabilities, making them suitable for use as innovative material components. The structural tunability, solvent effects, and external stimuli tunability of these transformations have made Stenhouse photoadducts attractive building blocks for demonstrating second-generation molecular machines. In recent times, the combination of powerful experimental methods has allowed a complete picture of their formation channels, excited-state dynamics, and energetic landscapes. This study critically examines the structural, mechanistic, and photophysical properties of Stenhouse photoadducts, as well as the dynamics of these properties in relation to the compounds' behavior under actual conditions. It explains the emerging applications of these compounds in molecular switches, data storage, sensing, and adaptive materials, as well as their current limitations, including poor stability and limited tunability. The review concludes with an opinion on additional areas of research to enhance the flexibility and functionality of systems based on Stenhouse. This analysis provides a detailed picture of existing knowledge and technological potential, which will help scientists develop photoresponsive molecular materials and explore the field of organic photochemistry.
Proteins govern cellular homeostasis through tightly regulated expression, localization, and interactions. Their dysregulation is the underlying cause of diseases ranging from cancer to neurodegeneration. Imaging of these dynamics in living systems therefore provides valuable information to understand not only biological phenomena but also pathogenesis. Although genetically encoded fluorescent proteins (FPs) enable live-cell imaging of proteins, they face several limitations, including susceptibility to photobleaching, scarcity of bright near-infrared (NIR) emitters, limited pulse-chase control, and bulky tags. To overcome these limitations, protein labeling techniques that use protein tags together with their specific fluorescent probes have been developed. These techniques afford superior photostability, near-infrared (NIR) compatibility, on-demand temporal labeling, and smaller tags. This review summarizes recent advances in fluorogenic probes for both covalent and noncovalent self-labeling tags, highlighting fluorescence regulation mechanisms that suppress background signals from free probes and promote emission upon protein labeling. The advantages and limitations of the probe design strategies are discussed, and then future perspectives on protein labeling techniques are described.
Photocatalytic small-molecule conversion by harnessing sunlight energy is of interest because of its potential to achieve artificial photosynthesis. This review explores the potential of conjugated polymers as CO2 reduction photocatalysts and highlights their unique molecular-level designs. Following the basic design principles of conventional metal complexes and semiconductor photocatalysts, the specific photocatalyst designs developed for conjugated polymers are summarized. This review further covers intermolecular hybridization with metal complexes and built-in approaches for site-selective catalyst incorporation, highlighting the importance of precisely tuning the energy levels for direction-selective photoinduced charge transport within both intermolecular and built-in hybrid photocatalysts to improve photocatalytic efficiency. Understanding and utilizing the characteristic features of molecular-based photocatalyst materials, including conjugated polymers, that enable molecular-level functional integration will facilitate the development of artificial photosynthetic reactions.
This paper reviews state-of-the-art spin-photonic devices, which are among the potential candidates, focusing on the development of circularly polarized light (CPL) devices and CPL applications. Initially, it introduces the differences in approaches between chemistry and physics for CPL emission research. Then, it explains the CPL emission mechanism of spin-polarized light-emitting diodes (Spin-LEDs), which are representative of spin-photonic devices. Subsequently, it discusses the functions of the lateral-type spin-LEDs, which have overcome the major challenge of achieving fully polarized CPL emission at room temperature, as well as helicity controllability and CPL detection. Finally, it introduces various proposed applications of CPL.
Aluminum, an earth-abundant, inexpensive, and lightweight metal, has recently attracted notable attention as a promising key element in photofunctional materials. Historically, aluminum complexes-most notably tris(8hydroxyquinolinato)aluminum-were among the earliest compounds explored for device applications. However, subsequent development in optoelectronics lagged behind systems based on boron, transition metals, and lanthanides. Over the past two decades (2005-2025), remarkable progress has been achieved in the molecular design, photophysical properties, and practical applications of aluminum complexes. This review summarizes recent advances in organometallic and coordination materials based on aluminum, beginning with an overview of the structural motifs and coordination environments that define these systems. We then highlight the key properties and emerging functions of aluminum complexes, with particular emphasis on luminescence, thermally activated delayed fluorescence, circularly polarized luminescence, crystallization-induced emission, aggregationinduced emission, and their applications in sensing and photocatalysis.
The near-infrared (NIR) spectral region plays a pivotal role in modern photonics and optoelectronics, yet most conventional semiconductors and molecular materials fail to utilize low-energy photons efficiently. Lanthanide (Ln)-based luminescent systems offer a unique means to overcome this limitation through two complementary photon conversion mechanisms—downconversion (or quantum cutting, QC) and upconversion (UC). In QC processes, a single high-energy photon is converted into two or more lower-energy photons via cooperative energy transfer between neighboring Ln ions (Ln3+), leading to photon multiplication and enhanced light-harvesting efficiency. Recent advances in QC-active materials, including Gd3+, Tb3+, and Yb3+-codoped oxides and fluorides, as well as emerging Ln3+-doped perovskite hosts, have demonstrated efficient UV/visible-to-NIR photon conversion, expanding the spectral coverage for photovoltaic and light-emitting device applications. In contrast, UC processes enable the stepwise absorption of multiple NIR photons to generate higher-energy visible or UV emission. To address the intrinsically weak absorption cross-sections of Ln ions, molecularly sensitized hybrid systems have been developed, where organic dyes act as broadband NIR antennae to mediate efficient energy transfer to Ln3+ centers. Additionally, core-shell and inorganic-passivated nanostructures have been engineered to suppress nonradiative quenching by controlling lattice phonons and surface states. The integration of Ln3+-based UC materials with halide perovskites further enables synergistic photon management, allowing sub-bandgap NIR photons to be utilized in solar cells and photodetectors. These developments illustrate a unified strategy for bidirectional photon conversion through QC and UV, paving the way toward next-generation energy-harvesting and photonic devices.
Photon upconversion based on triplet-triplet annihilation (TTA-UC) enables the conversion of low-energy photons into higher-energy ones, even under low-intensity, incoherent light. This process has recently gained renewed attention as a route toward efficient light-energy conversion for solar, photocatalytic, and biological technologies. Organic molecules exhibiting thermally activated delayed fluorescence (TADF) have recently attracted attention as efficient heavy-metal-free sensitizers owing to their strong visible-light absorption, efficient intersystem crossing (ISC), and tunable excited-state energy levels. The use of TADF compounds has expanded the accessible spectral window of TTA-UC, allowing large anti-Stokes shifts such as visible-to-UV and near-infrared (NIR)-to-visible TTA-UC. This review provides an overview of recent advances in TADF-sensitized TTA-UC systems and discusses the critical factors that determine their performance, including ISC dynamics, triplet energy transfer, and material stability. Challenges and prospects for designing efficient molecular architectures to achieve high TTA-UC efficiencies, lower threshold excitation intensities, and broader wavelength coverage are also highlighted.
Boron-dipyrromethene (BODIPY) dyes have emerged as transformative agents in precision biomedicine due to their exceptional photophysical properties including high molar absorption coefficients, tunable near-infrared (NIR) absorption/emission, superior photostability, and biocompatibility. This review comprehensively explores recent advances in BODIPY-based systems for diagnostic and therapeutic applications. We highlight their roles in in vitro and in vivo bioimaging (e.g., aldehyde detection, cytokine signaling visualization, super-resolution lysosomal tracking) and phototherapy (photodynamic therapy (PDT) and photothermal therapy (PTT)). Strategic molecular engineering enhances BODIPY performance, such as heavy-atom-free designs for improved intersystem crossing, J-aggregation for NIR photothermal conversion, and oxygen-independent Type I PDT for hypoxic tumors. Combinatorial approaches integrating PDT/PTT with chemotherapy or immunotherapy further amplify therapeutic efficacy. Despite promising outcomes, challenges in spectral optimization, in vivo targeting specificity, pharmacokinetics, and clinical translation persist. Future directions include low-power NIR-II activatable probes, stimuli-responsive nanoplatforms, and scalable biocompatible formulations. BODIPY-based theranostics hold immense potential to revolutionize precision oncology and antimicrobial therapy.
Photo-induced reactive oxygen species (ROS) are central to the selective oxidation of plastics and biomass, enabling efficient activation of inert C-H and C-C bonds under mild conditions-a crucial step toward bond cleavage and targeted functionalization. However, achieving precise control over the type, concentration, and spatial distribution of ROS remains challenging, especially for complex multicomponent substrates, as intermediate pathways depend critically on both ROS species and photocatalyst structure. This review systematically summarizes the formation and transformation mechanisms of radical and non-radical ROS and examines the direct role of photogenerated charges in oxidation. It demonstrates how rational catalyst design-through modulation of semiconductor properties, surface/interface structures, co-catalysts, and reaction conditions-can regulate ROS generation, evolution, and reactivity. Representative examples in plastic and biomass oxidation are discussed to illustrate how ROS and charge carriers drive selective depolymerization, monomer recovery, and functionalization via distinct mechanisms. Finally, this review highlights ongoing challenges in controlling ROS dynamics and elucidating their mechanistic roles, underscoring the need to correlate ROS behavior with reaction selectivity and product distribution.
Photothermal conversion is a fundamental yet rapidly evolving energy transformation processes that has consistently attracted significant research interest. Recent advances in photothermal nanomaterials have demonstrated their remarkable potential for biomedical applications. This review summarizes recent advances in photothermal nanomaterials, focusing on fundamental photothermal conversion mechanisms and representative material systems associated with each mechanism. Recent progress in applying photothermal materials for disease therapy and diagnosis is also systematically discussed. In therapy, strategies involving photothermal materials for tumor ablation, antibacterial therapy, and immunotherapy are described in detail. In diagnosis, photothermal properties are leveraged for multimodal bioimaging and highly sensitive detection of disease biomarkers. More recently, integrated strategies for multimodal diagnosis and therapy, along with their translational applications, have emerged as key research focuses. Finally, this review outlines key challenges and future prospects of photothermal nanomaterials in preclinical development. This review aims to advance next-generation photothermal nanomaterials and facilitate clinical translation of precision therapy and diagnosis to meet the growing demand for efficient, safe, and personalized healthcare.
Photocatalytic artificial photosynthesis mimics its natural counterpart by converting solar energy into chemical energy, producing organic molecules from CO2 and H2O. In particular, photocatalytic CO2 reduction with water as the electron donor offers a clean alternative to fossil-fuel-based processes and considered as a promising strategy toward carbon neutrality and environmental sustainability. For example, the conversion of CO2 and H2O to HCOOH and O-2 is thermodynamically uphill, with a standard Gibbs free-energy change of Delta G degrees similar to + 250 kJ mol(-1). Early related studies mainly examined semiconductors or molecular metal complexes as standalone photocatalysts. More recently, increasing attention has focused on semiconductor/metal complex hybrid systems, which couple the strong water-oxidation activity and robustness of semiconductors with the high CO2 reduction selectivity of metal complexes. Although particulate photocatalytic systems that use water as both the electron and proton source were once considered difficult to realize, recent studies have demonstrated highly selective C-1-product formation at appreciable rates by suppressing competing H-2 evolution. This minireview highlights recent advances in semiconductor/metal complex hybrid photocatalysts for CO2 reduction, covering both half-reactions that use sacrificial electron donors and fully uphill overall reactions that use water.
With growing concerns over fossil fuel depletion, hydrogen is widely recognized as a clean energy carrier with high energy density, but its storage and transport remain major challenges. As an alternative, formic acid has gained attention as a promising liquid organic hydrogen carrier due to its stability, non-toxicity, and ease of handling. Among various hydrogen release strategies, photocatalytic dehydrogenation of formic acid offers a sustainable route by utilizing sunlight under mild conditions via heterogeneous catalysis. In this review, we provide a comprehensive and mechanistic perspective on recent advances in photocatalytic formic acid dehydrogenation (FAD), with a unique classification into three core systems: plasmonic nanomaterial-based, semiconductor-based, and hybrid heterojunction-based photocatalysts, shifting focus from conventional material listings. Each section outlines the corresponding enhancement mechanisms, such as localized surface plasmon resonance-induced charge dynamics, Mott-Schottky junction formation, and interfacial charge transfer across heterostructures. A complete timeline of FAD research is introduced for the first time, providing historical and developmental context. This approach offers a structured understanding of recent progress and points toward future opportunities in sustainable hydrogen generation.
