Photochem

26 pages, 1521 KB

Open AccessReview

Mechanical Characterization of Natural Polymers Using Brillouin Spectroscopy: A Comprehensive Review

by José A. Rodrigues, Bruno Esteves, Patrícia Costa and José H. Correia

Photochem 2025, 5(4), 34; https://doi.org/10.3390/photochem5040034 - 23 Oct 2025

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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 [...] Read more.

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

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13 pages, 2362 KB

Open AccessArticle

Immune Gene Expression Modulation and In Vitro Inhibitory Effect of TiO₂ Nanoparticles Under UV Irradiation on Viral Necrosis Virus

by Rim El Jeni, Gian Luca Chiarello, Elena Selli, Annamaria Costa, Alessia Di Giancamillo, Daniela Bertotto, Giuseppe Radaelli, Tarek Temraz and Nadia Chérif

Photochem 2025, 5(4), 33; https://doi.org/10.3390/photochem5040033 - 16 Oct 2025

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Abstract

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 [...] Read more.

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

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19 pages, 1607 KB

Open AccessArticle

Upcycled Carbon Dots as Multifunctional Boosters for Broad-Spectrum Photostable Sunscreens

by Gustavo Teixeira Machado, Caio Rui Chiabai, Isaac dos Santos Orgino, Leticia Neves Ferraz, Flavia Dayrell França, Fábio Luiz Partelli, Paulo Eduardo Narcizo de Souza, Ana Sofia Fernandes, Ana Luísa Gomes Júlio, André Rolim Baby, George Ricardo Santana Andrade and Fabiana Vieira Lima Solino Pessoa

Photochem 2025, 5(4), 32; https://doi.org/10.3390/photochem5040032 - 13 Oct 2025

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Abstract

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, [...] Read more.

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

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12 pages, 1113 KB

Open AccessArticle

[2+2]-Photocycloadditions of 2-Acetoxy-1,4-naphthoquinone and Structure Determination of the Main Photoadducts

by Madyan A. Yaseen, Zhifang Guo, Peter C. Junk and Michael Oelgemöller

Photochem 2025, 5(4), 31; https://doi.org/10.3390/photochem5040031 - 10 Oct 2025

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Abstract

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 [...] Read more.

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

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18 pages, 3046 KB

Open AccessArticle

Simultaneous Photocatalytic CO₂ Reduction and Methylene Blue Degradation over TiO₂@(Pt, Au, or Pd)

by Elisenda Pulido-Melián, Cristina Valeria Santana-Fleitas, Javier Araña and Óscar Manuel González-Díaz

Photochem 2025, 5(4), 30; https://doi.org/10.3390/photochem5040030 - 28 Sep 2025

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Abstract

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, [...] Read more.

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

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14 pages, 926 KB

Open AccessReview

Biomedical Applications of Raman Spectroscopy: A Review

by Sara Pimenta and José H. Correia

Photochem 2025, 5(4), 29; https://doi.org/10.3390/photochem5040029 - 26 Sep 2025

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Abstract

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 [...] Read more.

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

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13 pages, 1438 KB

Open AccessReview

ROS Generation in the Light Reactions of Photosynthesis Triggers Acclimation Signaling to Environmental Stress

by Julietta Moustaka and Michael Moustakas

Photochem 2025, 5(4), 28; https://doi.org/10.3390/photochem5040028 - 25 Sep 2025

Viewed by 447

Abstract

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 [...] Read more.

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

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Photochem, Volume 5, Issue 4 (December 2025) – 7 articles

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