Designing chemically robust photoanodes capable of efficient oxygen evolution reaction (OER) in neutral media remains a central challenge for practical photoelectrochemical (PEC) water splitting. By experiment and theory herein we report the PEC OER functionality of a durable and mechanistically well-defined 2D-SnSe2/mesoporous TiO2 heterostructure photoanode operating at pH 7. Highly crystalline 2D-SnSe2 nanosheets (1.8 ± 0.1 μm lateral size and 100 ± 5 nm thickness) were solvothermally grown over mesoporous TiO2 films, forming a layered 2D-SnSe2/TiO2 heterojunction, with efficient carrier transport and strong interfacial adhesion, solving the common delamination problem of 2D/TiO2 systems. Under solar illumination, the 2D-SnSe2/TiO2 photoanode delivers a 16-fold higher current density than its single counterparts (0.80 mA/cm2 at 1.7 V vs RHE), together with excellent operational stability ( < 3% decay over 3 × 16 h continuous irradiation). Combining Mott–Schottky, valence-band XPS, and optical bandgap measurements with density functional theory (DFT), we reconstruct a defect-driven S-scheme charge-transfer mechanism, where oxygen vacancies in (110) TiO2 shift band edges to promote selective electron–hole recombination at the interface. Finally, differential free adsorption energies calculations of the four OER intermediates over oxygen defective (110) TiO2, indicate the OH* → O* transition as the potential-determining step. These results establish 2D-SnSe2/TiO2 as a stable, visible-light-responsive S-scheme heterostructure for neutral-pH OER, broadening the OER applications of group-IV chalcogenides MX2 (M = Sn, Ge; X = S, Se)/TiO2 photoanodes in neutral electrolytes.

The widespread description of carbon dots (C-dots) as semiconductor nanomaterials of quantum nature has become a diffuse paradigm in the field. This representation, although conceptually sounding at a first approach, is not supported for a large fraction of reported systems. In many cases, the optical response of C-dots arises, instead, from ensembles of localized, molecular-like emissive states, often coexisting with disordered carbon domains and surface defects. This review critically examines the origin and persistence of the semiconductor paradigm, tracing it to the early transfer of quantum dot terminology and to the reliance on limited characterization protocols. It is shown that commonly used descriptors, including band-gap estimation via Tauc analysis, frequently lack physical meaning in heterogeneous, multi-state systems. An operational categorization that replaces the binary semiconductor-versus-molecular ambiguity with three limiting classes is proposed. Molecular-state-dominated C-dots, hybrid core–surface systems, and graphenic/quantum-dot-like nanostructures. Each class is associated with specific structural signatures, photophysical properties, and levels of applicability of semiconductor descriptors. Photophysical interpretation directly impacts functional claims, particularly singlet oxygen generation and photocatalytic activity, where misassignment of electronic structure can lead to misleading mechanistic conclusions. The review suggests that progress in the field requires a shift from a unified but imprecise material identity to a class-resolved, evidence-driven approach, in which the structure-property relationships are supported by purification, molecular analysis, and direct probing of electronic structure.

The rapid growth of reports claiming the top-down synthesis of free-standing borophene from boron has generated substantial ambiguity regarding the true nature of the resulting materials. Here, representative sonication- and milling-based processing routes were investigated through multimodal structural, chemical, and optical characterization. Boron powders were treated by bath sonication in water, hydrogen peroxide, dimethylformamide, and isopropanol, as well as by ball milling under air and argon atmospheres. In all cases, no evidence of known borophene polymorphs was observed. Instead, the treatments produced fragmented β‑boron grains coated by defect-rich BxOy/B2O3 and boric-acid-derived surface species. Sonication promotes oxidation and hydrolysis, while ball milling induces partial amorphization and ultrathin oxide-layer formation. The observed photoluminescence originates from defect states in oxidized boron networks rather than from quantum confinement in putative borophene nanosheets. Processing in dimethylformamide can also induce solvent carbonization, potentially leading to misassignment of carbonaceous fluorescent species as boron nanostructures. These findings challenge current interpretations of top-down borophene synthesis and establish experimentally grounded criteria for distinguishing borophene from defect-mediated β‑boron-derived nanostructures.

Dihydroxynaphthalenes (DHN) provide a simple molecular platform to probe how hydroxy-group topology governs the interplay between antioxidant activity and photoinduced reactive oxygen species generation. Four regioisomeric dihydroxynaphthalenes (1,3-, 1,5-, 1,8-, and 2,7-DHN) have been investigated by combining steady-state spectroscopy, time-correlated single-photon counting, and femtosecond transient absorption with functional assays. The results show that intramolecular hydrogen bonding and π-electron delocalization control excited-state relaxation pathways, determining the balance between nonradiative energy dissipation and intersystem crossing. Peri-hydrogen-bonded 1,8-DHN exhibits the highest radical-scavenging efficiency while suppressing triplet formation and singlet-oxygen generation, whereas isomers lacking intramolecular hydrogen bonding display enhanced photosensitizing behavior. These findings establish hydroxy-group topology as a key structural parameter linking ground-state redox chemistry with excited-state photophysics.

The class of diamino-naphthalene exhibits antioxidant properties, which are partly related to the relative positions of the two amino groups. This study demonstrates how the reactivity of one of these compounds, 1,5-diamino-naphthalene (DAN), can be adjusted by introducing a single amide bond through a simple thermal coupling with l-pyroglutamic acid (PyroGlu). The solventless thermal reaction between PyroGlu and DAN at 160 °C yielded a new mono-pyroglutanilide compound (PyroDAN) that was characterized using various analytical techniques, including a thermal and infrared analysis, HRMS (ESI), and one- (1D) and two-dimensional (2D) NMR. The optical properties were investigated using UV-Vis and fluorescence spectroscopy. Additionally, two chemical standard assays were used to measure both the antioxidant and pro-oxidant properties of PyroDAN. The molecule has shown nearly negligible pro-oxidant activity, while a mild antioxidant activity is still retained. These findings indicate that the transformation of DAN into a mono-pyroglutanilide derivative breaks the original molecular symmetry and effectively modifies the electronic distribution of the aromatic system, suppressing the oxidant properties while keeping a mild antioxidant activity. Furthermore, the tuneable fluorescent properties of PyroDAN—the mild antioxidant activity and the inhibition of the cytologically harmful pro-oxidant properties—suggest promising applications in bioimaging and other biological fields.

The increasing need for effective antiviral strategies has led to the development of innovative surface coatings to combat the transmission of viruses via fomites. The aim of this review is to critically assess the efficacy of antiviral coatings in mitigating virus transmission, particularly those activated by visible light. The alarm created by the COVID-19 pandemic, including the initial uncertainty about the mechanisms of its spread, attracted attention to fomites as a possible source of virus transmission. However, later research has shown that surface-dependent infection mechanisms need to be carefully evaluated experimentally. By briefly analyzing virus–surface interactions and their implications, this review highlights the importance of shifting to innovative solutions. In particular, visible-light-activated antiviral coatings that use reactive oxygen species such as singlet oxygen to disrupt viral components have emerged as promising options. These coatings can allow for obtaining safe, continuous, and long-term active biocidal surfaces suitable for various applications, including healthcare environments and public spaces. This review indicates that while the significance of fomite transmission is context-dependent, advances in material science provide actionable pathways for designing multifunctional, visible-light-activated antiviral coatings. These innovations align with the lessons learned from the COVID-19 pandemic and pave the way for sustainable, broad-spectrum antiviral solutions capable of addressing future public health challenges.

Se rods decorated with SnO2 nanoparticles have been synthesized via a facile hydrothermal approach to bridge the gap between ultraviolet-only and visible-only photocatalysis and to enhance reactive oxygen species generation under visible illumination. Structural and morphological analyses using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy have confirmed the coexistence of cassiterite SnO2 particles intimately interfaced with trigonal selenium rods. Diffuse-reflectance spectroscopy revealed a long absorption tail extending into the 400-550 nm range. Under 450 nm sample illumination, the composite produced singlet oxygen in higher yields than either bare SnO2 or Se, as evidenced by the indocyanine green assay. The system alone does not produce free radicals, as shown by the terephthalic acid test; however, the addition of rhodamine B acts as an effective sensitizer, enabling hydroxyl radical generation. Photodegradation tests using rhodamine B have shown that the SnO2-Se system outperforms both its single components, Se and SnO2, as a catalyst. The synergistic interplay underscores the potential of SnO2-Se heterostructures in photochemical applications under visible light.

1,5-Diaminonaphthalene (DAN) is a small polyaromatic molecule known for its remarkable antioxidant properties. While its effective radical-scavenging activity under ambient conditions has been previously documented, this study unveils an equally compelling yet contrasting duality in the nature of this molecule. Indeed, DAN can also act as a photosensitizer under UV light irradiation, generating reactive singlet oxygen species, 1O2. We have studied the mechanisms underlying this dual behavior using a combination of characterization techniques, including FTIR, XRD, thermogravimetric analysis, UV-Vis spectroscopy, and electronic paramagnetic resonance. Without light, DAN efficiently neutralizes the 2,2-Diphenyl-1-picrylhydrazyl (DPPH & sdot;) radicals used as probe molecules through hydrogen atom transfer and exhibits antioxidant properties. However, under UV-light irradiation, DAN nature shifts dramatically. The photo-stimulation enables the production of reactive singlet oxygen with significant oxidative response, as demonstrated by the test with the standard probe indocyanine green. This light-triggered transformation highlights the versatility of DAN, bridging its use as a radical scavenger and pro oxidant. The findings pave the way for exploiting the dynamic redox properties of DAN in designing multifunctional nanomaterials where controlled oxidative and antioxidative responses are critical.

The synthesis of biocidal peptide materials using simple, low-cost, solvent-free methods is a crucial challenge for developing new antimicrobial approaches. In this study, we produced proteinoid nanostructures through simple, inexpensive, and environmentally friendly thermal reactions between glutamic acid (Glu) and tyrosine (Tyr) in various molar ratios. Mechanistically, the thermal cyclization of glutamic acid into pyroglutamic acid (pGlu) facilitated the formation of short peptide chains containing pGlu as the N-terminus moiety and subsequent L-tyrosine or glutamic acid residues, which self-assembled into nanometric spheroidal structures that exhibit blue emission. Spectroscopic (FTIR, UV-Vis, photoluminescence) and mass (LC-MS) analyses confirmed the formation of mixed pGlu-/Tyr/Glu peptides. All products exhibit dose-dependent antimicrobial activity against Methicillin-Resistant Staphylococcus aureus (MRSA), with a minimum inhibitory concentration (MIC) of 25 mg mL−1 for the GluTyr 1:1 and 2:1 proteinoids. The outcomes observed following 24 h exposure of the HEK293 cell line to the materials indicate their suitability for integration into hybrid systems for antimicrobial surfaces. This work is the first to demonstrate a direct antibacterial activity of proteinoids obtained by thermal condensation, opening up the possibility of designing a new class of synthetic antimicrobial peptides.

Sodium molybdate is a potential candidate as an effective antioxidant even if no significant proof of its antioxidant properties has been reported so far, especially for nanoparticles. In the present work, we have synthesised sodium molybdate nanoparticles using MoS2 and NaOH as precursors. After thermal treatment at 200 degrees C for 20 hours, sodium molybdate nanoparticles with an average dimension of 26 nm have been obtained. An intermediate treatment time of 8 hours gives nanoparticles with a mixed composition, MoS2-Na2MoO4. The nanoparticles have been characterized using Raman and infrared spectroscopy, X-ray diffraction, atomic force microscopy and dynamic light scattering. The radical scavenging capability has been tested using 1,1-diphenyl-2-picrylhydrazyl as a molecular probe. Both pure Na2MoO4 and the heterostructured MoS2-Na2MoO4 nanoparticles have exhibited excellent radical scavenging activity in aqueous solutions, with MoS2-Na2MoO4 showing an enhanced response. Another test has been conducted in the solid state, introducing the nanoparticles within a mesoporous titania film matrix. The high photocatalytic activity of titania has been completely quenched by the presence of the sodium molybdate nanoparticles. Finally, in vitro studies using Hep G2 cells further confirmed the antioxidant capacity of the nanoparticles without inducing cytotoxicity. These findings suggest that sodium molybdate nanoparticles are promising candidates for biomedical and environmental applications, particularly in reducing oxidative stress.

Carbon dots (CDs) are promising for agro-environmental applications; however, clear connections between synthesis, photophysical properties, size, and biosafety are often not well established. In this study, we map these relationships for glucose–arginine CDs (GA-CDs). By using microwave and hydrothermal routes at precursor ratios of 1:3, 1:9, and 1:15, we produced sub-10 nm nanoparticles (analyzed by dynamic light scattering and atomic force microscopy) that exhibit tunable absorption and emission properties, as well as surface properties (demonstrated through UV–Vis spectroscopy, 3D photoluminescence, and FTIR analysis). The hydrothermal 1:9 condition yielded the narrowest size distribution and red-shifted photoluminescence. Across biological models spanning plants, insects, plant-growth-promoting bacteria (PGPR), and human cells, GA-CDs were well tolerated, with no adverse changes detected in plant stress markers, aphid feeding behavior or fecundity, or PGPR growth. In A549 cells, viability remained stable up to a concentration of 0.125 mg mL−1, while exposure to 0.5 mg mL−1 reduced viability, establishing a practical operating range. These results provide a clearer picture of how the structure and properties of carbon dots derived from arginine and glucose are correlated to their safety. The GA-CDs are, therefore, useful, and traceable tools for agro-environmental research. The findings support their use as biocompatible nanomaterials for studying interactions among plants, insects, and microbes in agriculture.

Engineering emissive defects is key to developing fluorescent or phosphorescent compounds for optics and sensing applications in boron-based materials. The present work reports a bottom-up synthesis of boron oxide nanoparticles directly obtained from crystalline boron. The method does not employ organic solvents or harmful reactants and allows one to obtain pure boron oxide nanoparticles, avoiding the uncontrolled presence of carbon or other contaminants. The nanoparticles are formed through a two-step protocol: ultrasonication in water of bulk boron powder, followed by thermal annealing treatment in air. The first step allows for the formation of nanoparticles containing nonstoichiometric oxo-hydroxy BOH compounds, while the second induces dehydration and further oxidation of the boron species. The annealing temperature controls the number of defects formed during dehydration, and the defects modulate the nanoparticle fluorescence. The defects mainly comprise nonbridging oxygen within trigonal BO3 units, which have already proved to activate radiative pathways in the BOH system.

Sodium molybdate shows potential as an effective antioxidant, although limited studies on its antioxidant properties exist, and there are no reports concerning nanoparticles. In the present work we have synthesised...

The increasing need for effective antiviral strategies has led to the development of advanced surface coatings to combat the transmission of viruses via fomites. The Covid-19 pandemic has dramatically stimulated research in the field, and numerous advances have been made in understanding virus-surface interactions. A crucial step has been the experimental study of viral infection due to interactions with fomites. The alarm created by the pandemic, including the initial uncertainty about the mechanisms of infection spread, put the focus on fomites as a possible cause of virus transmission. Later research showed, however, that such a mechanism is implausible. The knowledge gained about fomites during the pandemic can be used to develop a new generation of biocidal coatings for bacteria and viruses that surfaces can actually transmit. In particular, biocidal coatings photoactivated by visible light represent a promising opportunity.

The discovery of borophene, a two-dimensional boron polymorph stabilized on metal substrates, has promoted intense efforts to obtain free-standing 2D boron sheets. Since its first epitaxial synthesis on Ag(111), several reports have claimed the formation of borophene sheets through mechanical or liquid-phase “exfoliation” of bulk β-rhombohedral boron. These claims, if correct, would represent a breakthrough in fabricating non-van der Waals bidimensional materials. In this review, we have critically evaluated the available experimental evidence in the published data. In the first part of the article, the structure of β-Boron (β-B) and borophene has been described; the presence and potential role of defects in producing 2D materials via top-down synthesis have been then analyzed. In the second part, we have discussed how the absence of van der Waals gaps in β-B precludes true “exfoliation” and is inconsistent with the theoretical framework. The formation of nanostructures upon “exfoliation” is better explained as defect-mediated cleavage formation of nanoscale intrinsic van der Waals gaps boron fragments, often oxidized, rather than true borophene polymorphs (β12, χ3). Based on this analysis, we propose diagnostic criteria for identifying the phases obtained through top-down synthesis processes starting from β-B. This critical review highlights how to avoid structural assignment errors and outlines best practices for phase identification in the search for 2D materials derived from non-layered solids.

Porphyrins are well-known photosensitizers with applications in photodynamic treatments for oncology and antimicrobial therapies, mainly due to their high singlet oxygen (1O2) quantum yield. However, challenges such as poor water solubility and complex multi-step synthetic procedure still hinder their clinical development. This study presents an innovative one-pot method for the synthesis of water-soluble and red-emitting porphyrin virucidal photosensitizers in the form of carbon polymer dots by direct thermal processing of glycine. We have made a significant stride by extending glycine condensation beyond the traditional formation of polypeptides, now achieving the remarkable generation and self-assembly of porphyrin derivatives within a carbonized polymeric matrix. The resultant "porphyrin-like dots" exhibit high water solubility, biocompatibility, strong photoluminescence and efficient 1O2 generation, as demonstrated by Indocyanine Green photodegradation tests. Notably, the dots also displayed significant photoinduced virucidal activity against Vaccinia virus, with up to 92 % inactivation at the highest concentration. These findings propose the produced porphyrin-like dots as promising theranostic tools for biomedical applications, combining potential diagnostic imaging and therapeutics functions.

Oxidative stress caused by reactive oxygen species is at the origin of several diseases, creating a need for a compelling new generation of antioxidant agents. This study reports on the synthesis of carbon dots (C-dots) from citric acid and evaluates their antioxidant properties. C-dots were obtained via a solventless thermal degradation of citric acid at 240 degrees C studying the process with in-situ temperature resolved infrared spectroscopy. The blueemitting fluorescent C-dots have an average dimension of 10 nm and exhibit antioxidant and oxidant activities. This surprising dual nature, in particular the ability of generating singlet oxygen under UV irradiation, was confirmed by colorimetric assays. The citric acid C-dots exhibited a radical scavenging efficiency of 90 % and retained the antioxidant activity for over six days, demonstrating high stability in aqueous environments and showing a better long-term stability than traditional antioxidants like ascorbic acid. These results emphasize the potential of citric acid C-dots in reducing the oxidative stress in different environments. These findings underscore the potential of citric acid-derived C-dots as versatile, stable, and cost-effective materials for mitigating oxidative stress. Moreover, when photo-stimulated by UV light, these C-dots behave as oxidant agent for singlet oxygen generation.