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The structural and electrical characteristics of (Mg, Zn)O ceramics produced using the solid state reaction at 1100 °C for 3 hours were studied applying X-ray diffraction and IR reflection spectroscopy as well as means of direct current measurements versus MgO content in initial charge (varied from 0 to 100 mol.%). It has been shown that electrical conductivity extracted from the IR reflection spectra corresponds to that of hexagonal phase in a solid solution, while plasmon in cubic phase was not observed. The electron concentration in the hexagonal grains of solid solution prepared with MgO content below 30 mol. % in the charge was found to be close to that of ZnO grains. It shows the tendency to decrease with further growth of the MgO content, which was explained by extraction of zinc interstitials, responsible for ZnO conductivity, from ZnO under formation of the MgZnO cubic phase. The direct current measurements have shown the lower conductivity as compared to the value estimated from IR reflection spectra. This fact along with the superlinearity of current-voltage characteristics has been explained by the presence of intergranular barriers, which does not allow obtaining information on the concentration of free electrons in the grain by this method. The possible nature of intergranular barriers as well as the role of grain boundaries in the DC conductivity of samples has been discussed. [ABSTRACT FROM AUTHOR]

The effect of Au nanoparticles (AuNPs) on the photoluminescence (PL) of AgInS2/ZnS quantum dots (QDs) in buffer solutions was investigated. The QDs stabilized with mercaptoacetic acid and glutathione were modified by 19-bases thiolated oligonucleotides, and the AuNPs grown in citrate solution and stabilized with lipoic acid and mercaptohexanol were modified by 26-bases thiolated oligonucleotide. These oligonucleotides are not complementary to each other. The nanoobjects were placed in buffer solutions of SSC with different dilutions (0.1 × , 0.25 × , 0.5 × SSC). The PL and optical absorption (OA) spectra of prepared solutions were studied. In the buffer solutions of different dilutions, the formation of aggregates of AuNPs depends on QDs' stabilizing ligands and presence/absence of oligonucleotides on AuNPs' surface, which was detected by specific changes in the OA spectra. The degree of PL quenching also was different in solution with modified and unmodified nanoobjects. The solutions were additionally incubated at room temperature for 24 h to see the dynamic of changing in the interaction between AuNPs and QDs, one of the manifestations of this interaction was an electrolytic aggregation. It is proposed that the observed decrease of PL intensity (PLI) in solutions with unmodified nanoobjects is due to the partial absorption of excitation light by AuNPs, and the interaction between QDs and AuNPs is caused by the presence of noncomplementary oligonucleotides on their surface. [ABSTRACT FROM AUTHOR]

The Zn2TiO4 ceramics doped with manganese of nominal content from 0.0016 to 1.6 mol% were produced by a solid-state reaction and investigated by the X-ray diffraction, photoluminescence (PL), diffuse reflectance spectroscopy and electron paramagnetic resonance (EPR) methods. The influence of sintering conditions (annealing temperature in the range of 800–1200 °C and atmosphere, Mn concentration) on Mn charge state and red PL has been studied. All samples contained a spinel Zn2TiO4 crystal phase with a minor amount of ZnO. The ceramics showed a PL band peaked at 680 nm, which was ascribed to 2Eg → 4A2g transition of Mn4+Ti in the Zn2TiO4. The PL intensity increased with annealing temperature and Mn concentration. The highest PL intensity was found in the samples with 0.1 mol% Mn sintered at 1100 °C. In the EPR spectra, the signals ascribed to residual Cr3+ in the Zn2TiO4, Mn2+ in the ZnO (g = 2.0014, A = 74.1 × 10−4 cm−1, b20 = 235 × 10−4 сm−1) and Mn2+ in the Zn2TiO4 (g = 1.987, A = 74.510 × 10−4 сm−1, b20 = 45 × 10−4 сm−1) were detected. The intensity of EPR signal due to Mn2+ in the Zn2TiO4 increased noticeably in the samples with 1.0 mol% Mn and in those sintered at 1200 °C. This was accompanied by the decrease of Mn4+ PL intensity. It is concluded that manganese dopes the Zn2TiO4 as both Mn4+ and Mn2+, the Mn2+ incorporation is strongly promoted by high annealing temperature (> 1100 °C) and high Mn concentration (~ 1 mol%). It is proposed that optical absorption of Mn-doped Zn2TiO ceramics in the visible spectral range is determined by spin allowed transition of Mn4+Ti and Mn2+/3+ donor-type photoionization transition in the Zn2TiO4. [ABSTRACT FROM AUTHOR]

Controlling the succession of chemical processes with high specificity in complex systems is advantageous for widespread applications, from biomedical research to drug manufacturing. Despite synthetic advances in bioorthogonal and photochemical methodologies, there is a need for generic chemical approaches that can universally modulate photodynamic reactivity in organic photosensitizers. Herein we present a strategy to fine-tune the production of singlet oxygen in multiple photosensitive scaffolds under the activation of bioresponsive and bioorthogonal stimuli. We demonstrate that the photocatalytic activity of nitrobenzoselenadiazoles can be fully blocked by site-selective incorporation of electron-withdrawing carbamate moieties and restored on demand upon uncaging with a wide range of molecular triggers, including abiotic transition-metal catalysts. We also prove that this strategy can be expanded to most photosensitizers, including diverse structures and spectral properties. Finally, we show that such advanced control of singlet oxygen generation can be broadly applied to the photodynamic ablation of human cells as well as to regulate the release of singlet oxygen in the semi-synthesis of natural product drugs., (© 2024. The Author(s).)

Despite advances in genome sequencing technology, the complete molecular interaction networks reflecting the biological functions of gene products have not been fully elucidated due to the lack of robust molecular interactome profiling techniques. Traditionally, molecular interactions have been investigated in vitro by measuring their affinity. However, such a reductionist approach comes with throughput constraints and does not depict an intact living cell environment. Therefore, molecular interactions in live cells must be captured to minimize false-positive results. The photo-cross-linking technique is a promising tool because the production of a temporally controlled reactive functional group can be induced using light exposure. Photoaffinity labeling is used in biochemistry and medicinal chemistry for bioconjugation, including drug and antibody conjugation, target protein identification of bioactive compounds, and fluorescent labeling of target proteins. This Account summarizes recent advances in multifunctional photo-cross-linkers for drug target identification and bioimaging. In addition to our group's contributions, we reviewed the most notable examples from the last few decades to provide a comprehensive overview of how this field is evolving. Based on cross-linking chemistry, photo-cross-linkers are classified as either (i) reactive intermediate-generating or (ii) electrophile-generating. Reactive intermediates generating photoaffinity tags have been extensively modified to target a molecule of interest using aryl azide, benzophenone, diazirine, diazo, and acyl silanes. These species are highly reactive and can form covalent bonds, irrespective of residue. Their short lifetime is ideal for the instant capture and labeling of biomolecules. Recently, photocaged electrophiles have been investigated to take advantage of their residue selectivity and relatively high yield for adduct formation with tetrazole, nitrobenzyl alcohol, o -nitrophenylethylene, pyrone, and pyrimidone. Multifunctional photo-cross-linkers for two parallel practical applications have been developed using both classes of photoactivatable groups. Unbiased target interactome profiling of small-molecule drugs requires a challenging structure-activity relationship study (SAR) step to retain the nature or biological activity of the lead compound, which led to the design of a multifunctional "minimalist tag" comprising a bio-orthogonal handle, a photoaffinity labeling group, and functional groups to load target molecules. In contrast, fluorogenic photo-cross-linking is advantageous for bioimaging because it does not require an additional bio-orthogonal reaction to introduce a fluorophore to the minimalist tag. Our group has made progress on minimalist tags and fluorogenic photo-cross-linkers through fruitful collaborations with other groups. The current range of photoactivation reactions and applications demonstrate that photoaffinity tags can be improved. We expect exciting days in the rational design of new multifunctional photo-cross-linkers, particularly clinically interesting versions used in photodynamic or photothermal therapy.