Photochem, Volume 5, Issue 4 (December 2025) – 13 articles

Gold nanoparticles (AuNPs) synthesized via picosecond pulsed laser ablation were investigated as enhancers of methylene blue (MB)-mediated photodynamic therapy (PDT) against Escherichia coli. AuNPs produced at 532 and 1064 nm with frequencies of 20–50 kHz showed frequency- and size-dependent effects, with 50 kHz yielding the highest particle concentrations and smaller particles enhancing reactive oxygen species (ROS) generation. UV-Vis and fluorescence spectroscopy confirmed nanoparticle formation and plasmonic properties consistent with TEM measurements. Photobleaching assays demonstrated that AuNPs significantly increased MB singlet oxygen generation, while the efflux pump inhibitor INF-55 further amplified bacterial killing without altering net ROS yield. In vitro assays revealed that INF-55 combined with MB/AuNPs achieved ~59% higher bacterial deactivation compared to MB/AuNPs alone. Molecular docking confirmed stronger binding of INF-55 to the AcrB efflux pump (−9.1 kcal/mol) than MB, supporting its role as a competitive inhibitor that promotes intracellular MB retention. These findings establish a dual-action PDT strategy in which AuNPs enhance ROS production and INF-55 augments antibacterial efficacy via efflux pump inhibition. Together, this platform provides a proof of concept for future translation to biofilm- and tissue-based infection models, and potentially to localized clinical applications such as prosthetic joint, catheter-associated, or chronic wound infections where conventional sterilization or systemic antibiotics are insufficient. Full article

Natural Product Synthesis (NPS) is a cornerstone of organic chemistry, historically rooted in the dual goals of structure elucidation and synthetic strategy development for bioactive compounds. Initially focused on identifying the structures of medicinally relevant natural products, NPS has evolved into a dynamic field with applications in drug discovery, immunotherapy, and smart materials. This evolution has been propelled by advances in reaction design, mechanistic insight, and the integration of green chemistry principles. A particularly promising development in NPS is the use of photochemistry, which harnesses light—a renewable energy source—to drive chemical transformations. Photochemical reactions offer unique excited-state reactivity, enabling synthetic pathways that are often inaccessible through thermal methods. Their precision and sustainability make them ideal for modern synthetic challenges. This review explores a wide range of photochemical reactions, from classical to contemporary, emphasizing their role in total synthesis. By showcasing their potential, the review aims to encourage broader adoption of photochemical strategies in the synthesis of complex natural products, promoting innovation at the intersection of molecular complexity, sustainability, and synthetic efficiency. Full article

Long persistent phosphors are widely used in many fields, such as LED, bioimaging, urgent lighting, temperature sensors, etc. Although green and blue long persistent phosphors are well developed, efficient orange-yellow long persistent phosphors are still relatively rare. In this work, a novel orange-yellow long-persistent phosphors Ca₂LuScGa₂Ge₂O₁₂:xPr³⁺ (CLSGGO:xPr³⁺, x = 0.003, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05) are prepared and systematically investigated through its crystal structural information, photoluminescence, and persistent luminescence properties. Under ultraviolet light excitation, these phosphors exhibit orange-yellow emission stemming from the ³P₀ and ¹D₂ multiple electron transitions in the 4f level of Pr³⁺ ion. In addition, the material exhibits bright persistent luminescence. The complex garnet matrix structure of Ca₂LuScGa₂Ge₂O₁₂ provides excellent conditions for the formation of traps. Through the testing of thermoluminescence curve and function fitting, the density and depth of traps are studied; also, the storage and release process of carriers in the material are calculated in detail. A reasonable persistent luminescence mechanism is proposed for CLSGGO:0.01Pr³⁺. This work enriches the research content of photoluminescence and long persistent luminescence of Pr³⁺-doped garnet-based phosphors and paves the way for the future research of long persistent luminescent materials doped with rare earth ions. Full article

In this study, the fluorescence (FL) behavior of a fluorenone derivative (FDMFA) in four chlorinated hydrocarbon solvents was investigated. While all four solvents have low polarities, their proticities are considerably different. Therefore, the FL properties of FDMFA could be considered to depend solely on the solvent’s proticity, with any polarity effects being insignificant. The hydrogen bond donor acidity was used as a measure of proticity, with higher values representing greater FL quenching due to vibronic coupling. The hydrogen bonding between FDMFA and the solvents could be thermodynamically controlled; thus, the FL emission was substantially enhanced during the heating process and quenched again during the cooling process. This change occurred reversibly and repeatedly. Because chlorinated hydrocarbon solvents are widely used for reaction and cleaning purposes in industrial applications, the findings of this study will be helpful in ensuring that such solvents are appropriately handled. Full article

Organic luminogens (OLs) with piezochromic (PC) properties have attracted significant attention for their varied applications in chemical sensors, organic optoelectronic devices, biological imaging, etc. In this work, we designed and synthesized three donor–acceptor–donor- or donor–acceptor-structured OLs with different donor or acceptor moieties. Their photophysical properties in both dilute solution and aggregated states were studied through various spectroscopic analytical methods, and their PC properties were investigated under mechanical grinding (MG) conditions. The OLs containing cyanostilbene moiety exhibited a photoemission shift up to ~45 nm after simple grinding, while that was only ~10 nm for cyanostyrene-containing OL. Combined with the powder X-ray diffraction analysis, the incorporation of the cyanostilbene moiety is inferred to play an important role in inducing the apparent PC properties. Our study not only reports novel OLs with good PC properties, but also discusses the structure–property relationships in order to provide guidance for future rational design and the development of novel PC materials. Full article

Biocatalysis is fundamental to biological processes and sustainable chemical productions. Over time, the biocatalysis strategy has been widely researched. Initially, biomanufacturing and catalysis of high-value chemicals were carried out through direct immobilization and application of biocatalysts, including natural enzymes and living cells. With the evolution of green chemistry and environmental concern, hybrid photoelectro-biocatalysis (HPEB) platforms are seen as a new approach to enhance biocatalysis. This strategy greatly expands the domain of natural biocatalysis, especially for bio-based components. The selective valorization of renewable furan derivatives, such as 5-hydroxymethylfurfural (HMF) and furfural, is central to advancing biomass-based chemical production. Biocatalysis offers high chemo-, regio-, and stereo-selectivity under mild conditions compared with traditional chemical catalysis, yet it is often constrained by the costly and inefficient regeneration of redox cofactors like NAD(P)H. Photoelectrocatalysis provides a sustainable means to supply reducing equivalents using solar or electrical energy. In recent years, hybrid systems that integrate biocatalysis with photoelectrocatalysis have emerged as a promising strategy to overcome this limitation. This review focuses on recent advances in such systems, where photoelectrochemical platforms enable in situ cofactor regeneration to drive enzymatic transformations of furan-based substrates. We critically analyze representative coupling strategies, materials and device configurations, and reaction engineering approaches. Finally, we outline future directions for developing efficient, robust, and industrially viable hybrid catalytic platforms for green biomass valorization. Full article

Experimental analysis of the viscoelastic properties of natural polymers over different testing durations and response time scales yields complementary insights into their static and dynamic mechanical behavior. Within this context, Brillouin spectroscopy has emerged as a contactless, non-invasive and label-free tool for the mechanical characterization of materials. In this review article, we provide a comprehensive overview of recent advances in Brillouin spectroscopy techniques applied to various natural polymers, including proteins, carbohydrates, and polysaccharides. We discuss the principles of Brillouin scattering and their application in investigating the mechanical properties of natural polymers. Additionally, we explore future perspectives and challenges. This review aims to provide researchers and practitioners with a comprehensive understanding of the capabilities and limitations of Brillouin spectroscopy for the mechanical characterization of natural polymers, promoting new advances in this interdisciplinary field. Full article

This study examines the potential in vitro application of different concentrations of titanium dioxide (TiO₂) nanoparticles (NPs) irradiated with UV light for the sanitation of recirculating aquaculture systems (RASs) and their antiviral activity. The diverse effects of Nodavirus on immune gene expression (i.e., pro-inflammatory and anti-inflammatory genes, cellular response genes, humoral response genes, and stress genes) were studied using RT-qPCR (Reverse Transcription Quantitative Polymerase Chain Reaction). In addition, the viability and cytopathic effect in E-11 fish cells were also investigated. The results obtained did not show a clear cytopathic effect under the reversed-phase microscope observation at different TiO₂ concentrations. A significant decrease in viral coat protein gene expression was observed when using 2.5 and 1.25 g/L TiO₂ suspensions under UV irradiation. TiO₂ at 1.25 g/L induced an inflammatory response to Nodavirus by increasing the expression of all target genes. Thus, this work suggests that TiO₂ NPs can strengthen the immune system of fish to fight virus infection and make aquaculture a greener and more sustainable activity. Full article

Sustainable ultraviolet (UV) filters that couple photoprotection with antioxidant activity are needed. Carbon dots (CDots) derived from agro-industrial waste have emerged as promising candidates. CDots were prepared from Coffea canephora (coffee leaf) residues by a one-pot microwave route and characterized by UV–Vis, FTIR, and TEM. Antioxidant capacity was determined by CUPRAC and DPPH-EPR. The photoprotective efficacy was assessed in vitro by diffuse reflectance spectrophotometry before and after solar-simulator exposure. Nearly spherical CDots (3.3 ± 0.7 nm) displayed a 4.16 eV optical bandgap and broad absorption from 200 to 400 nm. At 10 μg mL⁻¹, CDots exhibited 24.62 ± 0.19% antioxidant activity relative to Trolox by CUPRAC, while by DPPH-EPR, they showed 99.9 ± 12.5% of radical quenching at 240 µg mL⁻¹. Addition of 4.5% w/w (dry basis) CDots to the sunscreen system increased the in vitro SPF from 26 ± 13 to 161 ± 8 (p < 0.05) while maintaining the critical wavelength at 380 ± 0.64 nm. After 30 min of irradiation, the SPF dropped only 10%, versus 44% for the CDots-free sample (control), indicating superior photostability. Coffee leaf CDots acted as an efficient broadband UV absorber and antioxidant that markedly enhanced and stabilized a conventional sunscreen formulation. The work positions waste-derived CDots as an eco-friendly, next-generation multifunctional ingredient, aligning with circular economy principles. Full article

The [2+2]-photocycloaddition of 2-acetoxy-1,4-naphthoquinone with 1,1-diphenylethylene, styrene and cyclopentene was conducted in a conventional batch reactor. Prolonged irradiation selectively produced the corresponding anti and head-to-head cyclobutanes in acceptable to good yields. The batch process was subsequently transferred to continuous-flow operation in a simple capillary device. Likewise, the photocycloaddition with diphenylacetylene gave the corresponding cyclobutene and a benzoanthracenone derivative in acceptable yields. The crystal structures of all main photoproducts were successfully determined. Full article

In this work, the photocatalytic reduction of CO₂ was innovatively tested with the simultaneous removal and mineralization of a textile contaminant, methylene blue (MB), which acts as a sacrificial agent. The process was carried out in a flow regime under atmospheric conditions, using a liquid-phase photoreactor under UVA illumination with a duration of 24 h per test. Two commercial TiO₂-based photocatalysts, P25 and P90 from Evonik, were used and surface modified through the photodeposition of metallic nanoparticles of Pt, Au, and Pd, as they did not show gas-phase products from CO₂ reduction on their own. The optimal pH was 5, the decreasing order of activity by metal was Pt > Au > Pd, and the optimal MB concentration was 20 ppm. The major products were CH₄ and H₂ in the gas phase. The presence of CH₄ was only detected in the presence of a CO₂ flow. In the liquid phase, carboxylic acids were also detected in small amounts, and in the test, 100 ppm of MB ethanol was additionally detected. A 100% degradation of MB and 72.5% mineralization was achieved under the conditions of highest CH₄ production (20 ppm MB at pH 5 with 4 g·L⁻¹ P25-0.70%Pt). Full article

Raman spectroscopy is a widely used technology in the biomedical field, including specific applications from cancer diagnosis to an active role in the pharmaceutical industry. Despite the extensive use of Raman spectroscopy in research studies, there are still some limitations to its applicability in daily clinical diagnosis. This review initially presents the main principles of Raman spectroscopy and then its most relevant applications in the biomedical field, exploring the main advantages, challenges, and limitations. Additionally, other Raman-based techniques are identified as alternatives to the conventional technique. Overall, this review aims to present the currently available applications of Raman spectroscopy in the biomedical field and future appropriate perspectives, as possible guidance for new Raman-based biomedical devices. Full article

In the light reactions of photosynthesis, reactive oxygen species (ROS), such as superoxide anion radical (O₂^•−), hydrogen peroxide (H₂O₂), singlet oxygen (¹O₂*), and hydroxyl radical (OH^•), are continuously generated at basal levels and are kept in homeostasis by the antioxidative enzymatic and non-enzymatic systems. Nevertheless, under abiotic or biotic stress conditions, this balance between the creation and elimination of ROS is disrupted, and the increased ROS production leads to oxidative stress, which is involved in the growth retardation of plants. However, ROS are also beneficial, since they trigger the plant’s defense mechanisms for handling oxidative stress and are fundamental signaling molecules for the regulation of a range of physiological functions under optimum growth conditions or environmental stress circumstances, activating a plethora of acclimation responses. Gaining insight into the relationship between ROS generation, ROS scavenging, and the protective role of ROS will contribute to improving agricultural sustainability in the face of global climate change. Full article