Insights into the phototautomerism of free-base 5, 10, 15, 20-tetrakis(4-sulfonatophenyl) porphyrin

: Phototautomerism in the excited states of free-base 5, 10, 15, 20-tetrakis(4-sulfonatophenyl) porphyrin (H2TPPS4-) has been investigated combining, for the first time, advanced Electron Paramagnetic Resonance (EPR) with fluorescence and Raman spectroscopy. Triplet EPR spectroscopy, performed in protic and deuterated solvents and in the presence of photoselection, confirms the occurrence of phototautomerization and additionally suggests the formation of the cis tautomer as a minor component. The zero-field splitting parameters and triplet sublevel populations indicate that the process is slow in the triplet state. The results obtained by EPR combined with photoselection and fluorescence anisotropy have been interpreted within a model which accounts for a fast trans-trans tautomerization promoted by a spin-vibronic coupling mechanism for intersystem crossing, with an even distribution of the two trans tautomers at liquid nitrogen temperatures for H2TPPS4-

Excitation Wavelength- and Medium-Dependent Photoluminescence of Reduced Nanostructured TiO2 Films

The performance of TiO2 nanomaterials in solar energy conversion applications can be tuned by means of thermal treatments in reducing atmospheres, which introduce defects (such as oxygen vacancies), allowing, for instance, a better charge transport or a higher photocatalytic activity. The characterization of these defects and the understanding of their role are pivotal to carefully engineer the properties of TiO2, and, among various methods, they have been addressed by photoluminescence (PL) spectroscopy. A definitive framework to describe the PL properties of TiO2, however, is still lacking. In this work, we report on the PL of nanostructured anatase TiO2 thin films, annealed in different atmospheres (oxidizing and reducing), and consider the effects of different excitation energies and different surrounding media on their PL spectra. A broad PL signal centered around 1.8–2.0 eV is found for all the films with UV excitation in air as well as in vacuum, while the same measurements in ethanol lead to a blueshift and to intensity changes in the spectra. On the other hand, measurements with different sub-bandgap excitations show PL peaking at 1.8 eV, with an intensity trend only dependent on the thermal treatment and not on the surrounding medium. The results of PL spectroscopy, together with electron paramagnetic resonance spectroscopy, suggest the critical role of oxygen vacancies and Ti3+ ions as radiative recombination centers. The complex relationship between thermal treatments and PL data in the explored conditions is discussed, suggesting the importance of such investigations for a deeper understanding on the relationship between defects in TiO2 and photoactivity

Stabilization of linear carbon structures in a solid Ag nanoparticle assembly

Linear sp carbon nanostructures are gathering interest for the physical properties of one-dimensional (1D) systems. At present, the main obstacle to the synthesis and study of these systems is their instability. Here we present a simple method to obtain a solid system where linear sp chains (i.e. polyynes) in a silver nanoparticle assembly display a long term stability at ambient conditions. The presence and the behavior of linear carbon is investigated by Surface Enhanced Raman Scattering (SERS) exploiting the plasmon resonance of the silver nanoparticles assembly. This model system opens the possibility to investigate an intriguing form of carbon nanostructures

IQGAP1 and NWASP promote human cancer cell dissemination and metastasis by regulating β1-integrin via FAK and MRTF/SRF

Data and code availability: * All data are available in the main text or the supplementary materials. Original western blot images are in the supplemental material. Blot and imaging data reported in this paper will be shared by the lead contact upon request. * This paper does not report original code. * Any additional information required to reanalyze the data reported in this paper is available from the lead contact, Anne Ridley ([email protected]). upon request.Supplemental information is available online at: https://www.cell.com/cell-reports/fulltext/S2211-1247(24)00317-6?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2211124724003176%3Fshowall%3Dtrue#supplementaryMaterial .Summary: Attachment of circulating tumor cells to the endothelial cells (ECs) lining blood vessels is a critical step in cancer metastatic colonization, which leads to metastatic outgrowth. Breast and prostate cancers are common malignancies in women and men, respectively. Here, we observe that β1-integrin is required for human prostate and breast cancer cell adhesion to ECs under shear-stress conditions in vitro and to lung blood vessel ECs in vivo. We identify IQGAP1 and neural Wiskott-Aldrich syndrome protein (NWASP) as regulators of β1-integrin transcription and protein expression in prostate and breast cancer cells. IQGAP1 and NWASP depletion in cancer cells decreases adhesion to ECs in vitro and retention in the lung vasculature and metastatic lung nodule formation in vivo. Mechanistically, NWASP and IQGAP1 act downstream of Cdc42 to increase β1-integrin expression both via extracellular signal-regulated kinase (ERK)/focal adhesion kinase signaling at the protein level and by myocardin-related transcription factor/serum response factor (SRF) transcriptionally. Our results identify IQGAP1 and NWASP as potential therapeutic targets to reduce early metastatic dissemination.This work was funded by a Cancer Research UK grant (C6620/A15961) (A.J.R., C.C., R.G., and N.R.), the University of Bristol School of Cellular and Molecular Medicine (A.J.R. and C.C.), a Cancer Research UK Oxford Center DPhil Prize Studentship (BBRTJW00) (S.L.), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement (no. 655817) MSCA-IF-2014 (S.T.M. and A.R.), a Cancer Research UK grant A1731 (R.M.), and the Biotechnology and Biological Sciences Research Council (grant no. BB/K009184/1) (I.A.R.)

Supermultiplexed optical imaging and barcoding with engineered polyynes

Optical multiplexing has a large impact in photonics, the life sciences and biomedicine. However, current technology is limited by a 'multiplexing ceiling' from existing optical materials. Here we engineered a class of polyyne-based materials for optical supermultiplexing. We achieved 20 distinct Raman frequencies, as 'Carbon rainbow', through rational engineering of conjugation length, bond-selective isotope doping and end-capping substitution of polyynes. With further probe functionalization, we demonstrated ten-color organelle imaging in individual living cells with high specificity, sensitivity and photostability. Moreover, we realized optical data storage and identification by combinatorial barcoding, yielding to our knowledge the largest number of distinct spectral barcodes to date. Therefore, these polyynes hold great promise in live-cell imaging and sorting as well as in high-throughput diagnostics and screening

Femtosecond Dynamics of the Ring Closing Process of Diarylethene: A Case Study of Electrocyclic Reactions in Photochromic Single Crystals

The cyclization reaction of the photochromic diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene was studied in its single crystal phase with femtosecond transient absorption spectroscopy. The transient absorption measurements were performed with a robust acquisition scheme that explicitly exploits the photoreversibility of the molecular system and monitors the reversibility conditions. The crystalline system demonstrated 3 × 104 repeatable cycles before significant degradation was observed. Immediately following photoexcitation, the excited state absorption associated with the open-ring conformation undergoes a large spectral shift with a time constant of approximately 200 fs. Following this evolution on the excited state potential energy surface, the ring closure occurs with a time constant of 5.3 ps, which is significantly slower than previously reported measurements for similar derivatives in the solution phase. Time resolved electron diffraction studies were used to further demonstrate the assignment of the transient absorption dynamics to the ring closing reaction. The mechanistic details of the ring closing are discussed in the context of prior computational work along with a vibrational mode analysis using density functional theory to give some insight into the primary motions involved in the ring closing reaction

CZTS absorber layer for thin film solar cells from electrodeposited metallic stacked precursors (Zn/Cu-Sn)

In the present work, Kesterite-Cu2ZnSnS4 (CZTS) thin films were successfully synthesized from stacked bilayer precursor (Zn/Cu-Sn) through electrodeposition-annealing route. Adherent and homogeneous Cu-poor, Zn-rich stacked metal Cu-Zn-Sn precursors with different compositions were sequentially electrodeposited, in the order of Zn/Cu-Sn onto Mo foil substrates. Subsequently, stacked layers were soft annealed at 350 °C for 20 min in flowing N2 atmosphere in order to improve intermixing of the elements. Then, sulfurization was completed at 585 °C for 15 min in elemental sulfur environment in a quartz tube furnace with N2 atmosphere. Morphological, compositional and structural properties of the films were investigated using SEM, EDS and XRD methods. Raman spectroscopy with two different excitation lines (514.5 and 785 nm), has been carried out on the sulfurized films in order to fully characterize the CZTS phase. Higher excitation wavelength showed more secondary phases, but with low intensities. Glow discharge optical emission spectroscopy (GDOES) has also been performed on films showing well formed Kesterite CZTS along the film thickness as compositions of the elements do not change along the thickness. In order to investigate the electronic structure of the CZTS, Photoluminescence (PL) spectroscopy has been carried out on the films, whose results matched up with the literatures