An Efficient Visible and Near‐Infrared (NIR) Emitting SmIII Metal–Organic Framework (Sm‐MOF) Sensitized by Excited‐State Intramolecular Proton Transfer (ESIPT) Ligand

We report herein an unprecedented example of a luminescent Sm^III metal–organic framework (Sm‐MOF), in which both the visible and near‐infrared (NIR) emissions of Sm³⁺ ions are able to be sensitized by an excited‐state intramolecular proton transfer (ESIPT) ligand. Due to the solvent‐mediated interchange between enol and keto excited states of the ligand and subsequent energy transfer rate to Sm³⁺ ions, the luminescent decay lifetime of the Sm‐MOF can be tuned in different solvent‐grinding systems.     

Homogenous Boron‐doping in Self‐sensitized Carbon Nitride for Enhanced Visible‐light Photocatalytic Activity

We report a solvothermal approach for the preparation of homogeneously B‐doped self‐sensitized carbon nitride (B‐SSCN) composed of a core of B‐doped carbon nitride microspheres and a covalently linked shell of s‐triazine oligomers. Compared to the undoped structure, the obtained B‐SSCN photocatalyst exhibits an enhanced visible‐light activity, excellent stability for photocatalytic hydrogen generation due to a reduced band‐gap, enhanced charge‐separation efficiency, and better surface reactivity of B‐SSCN. This work provides a new strategy to uniformly insert heteroatoms into the polymeric carbon nitride framework for the development of metal‐free photocatalysts towards efficient production of solar fuels.     

Front Cover: Design,Synthesis and Photophysical Studies of Luminescent Rhodium(III) Complexes in Near-Infrared Region (Eur. J. Inorg. Chem. 11/2023)

A series of near-infrared (NIR)-emitting cyclometalated rhodium(III) complexes have been designed, synthesized and characterized. The NIR luminescence has been realized by rational design of strong σ-donor cyclometalating (C^N) ligand with extended π-conjugation structure for decreasing the energy level of intraligand (IL) state. In addition, the investigation of substituents on the benzo[g]quinoxaline moiety as the carbon-donor demonstrated that the luminescence can be further shifted to the red by the introduction of electron-donating thienyl groups. The luminescence maxima of these complexes are ranging from 763 nm to 792 nm with the luminescence quantum yield (Φ_lum) of 0.41 %–0.66 % in dichloromethane solution. This work demonstrates the first example of NIR-phosphorescent rhodium(III) complexes and provides an alternative for diversifying the development of NIR materials.     

Screening of humic and fulvic acids in estuarine sediments by near-infrared spectrometry

Diffuse reflectance near-infrared spectroscopy (NIR) combined with partial least squares (PLS) data treatment has been employed for the rapid and nondestructive determination of sedimentary humic substances. Forty one samples of surface estuarine sediments, taken during distinct seasonal periods from different locations across Ria de Arousa (northwest of Spain), were scanned at wavelengths from 833 to 2,976 nm (12,000 to 3,360 cm⁻¹). Twenty four samples were randomly selected, from previous hierarchical cluster analysis of their NIR spectra, for the calibration set, and the 17 remaining samples were assigned to the validation set. NIR spectra of calibration samples were correlated to measured values of humic acids (HAs) and fulvic acids (FAs), which ranged from 1.53 to 28.17 mg/g and from 0.37 to 2.45 mg/g, respectively, using PLS regression and multiplicative scattering correction on the raw and first-derivative NIR spectra, respectively. Low root mean square error of prediction values of 4.3 mg HA/g sediment and 0.25 mg FA/g sediment were obtained. Good residual prediction deviation values of 1.16 and 1.2 were obtained for HA and FA, respectively, allowing the PLS models built to be considered as appropriate tools for screening purposes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Establishment of “one-piece” large-gel 2-DE for high-resolution analysis of small amounts of sample using difference gel electrophoresis saturation labelling

Large-gel two-dimensional gel electrophoresis (2-DE) is the method of choice for high-resolution proteome analysis of complex protein mixtures. Until now, however, the advantages of large 2-DE in combination with multiplexed fluorescence dye protein labelling has been complicated by the separate handling and analysis of the second-dimension gels. Therefore, we adapted the large 2-DE procedure allowing us to run “one-piece” large 2-DE gels (40 cm × 30 cm) in the second dimension for high resolution proteome analysis. Here, we show that in combination with fluorescence dye protein saturation labelling “one-piece” large 2-DE enables analysis of small amounts of sample (3 μg protein) for high-resolution proteome analysis.     

Efficiency enhancement of solid‐state dye sensitized solar cell by in situ deposition of CuI

Solid‐state dye‐sensitized solar cells based on nanocrystalline TiO₂ thin film with the structures TiO₂/dye/CuI/Pt and TiO₂/dye/In situ CuI/CuI/Pt were developed in order to compare the use of In situ deposited CuI (In situ CuI). Porosity of the screen‐printed nanoporous TiO₂ thin film was enhanced by the addition of polystyrene balls. Evidence of decrease in interfacial resistance was observed by electrochemical impedance measurement for the device with In situ deposited CuI as compared to that without In situ deposited CuI as hole conductor. This was attributed to good interfacial contacts and better charge transfer between CuI and dye‐sensitized TiO₂ nanoparticles, which resulted in the enhancement of power conversion efficiency from 0.058 to 1.01%. Copyright © 2008 John Wiley & Sons, Ltd.     

Use of UV-visible spectroscopy to monitor nitrocellulose degradation in thin films

Activation energies for nitrocellulose (NC) degradation have been determined from Arrhenius plots constructed using first-order rate constants measured at 40, 50 and 60 °C. The rate constants were obtained by monitoring the absorbance (A) at a wavelength in the visible region of an anthraquinone dye dispersed in NC thin films. The dye acts as a stabilizer and is slowly depleted as a result of its reaction with NO_x from the breakdown of the nitrate ester groups on NC. The data produced two linear regions in the first-order plots of ln(A₀/A_t) vs aging time. The first-region is attributed to the reaction of the dye with NO_x desorbed from the NC surface. The activation energy (∼73.5 kJ mol⁻¹) is in line with that found for NO_x surface desorption processes. The second linear region is thought to be due to the reaction of NO_x from the breakdown of the nitrate ester groups on the NC molecule. The activation energy (∼104.0 kJ mol⁻¹) is consistent with that for nitrate ester hydrolysis. The use of UV-visible spectroscopy has in this way made it possible to monitor the degradation of NC non-destructively without the need for stabilizer extraction and analysis.     

Focusing and stabilization of bis‐intercalating dye–DNA complexes for high‐sensitive CE‐LIF DNA analysis

Multiple labeling of nucleic acids by intercalative dyes is a promising method for ultrasensitive nucleic acid assays. The properties of the fast dissociation and instability of dye–DNA complexes may prevent from their wide applications in CE‐LIF nucleic acid analysis. Here, we describe an optimum CE focusing method by using appropriately paired sample and separation buffers, Tris‐glycine buffer and Tris‐glycine‐acetic acid buffer. The developed method was applied in both uncoated and polyacrylamide coated fused‐silica capillary‐based CE‐LIF analysis while the sample and separation buffers were conversely used. The complexes of intercalative dye benzoxazolium‐4‐pyridinium dimer and dsDNA were greatly focused (separation efficiency: 1.8 million theoretical plates per meter) by transient isotachophoresis mechanism in uncoated capillary, and moderately focused by transient isotachophoresis in combination of field amplified sample stacking and further stabilized by the paired buffer in polyacrylamide coated capillary. Based on the developed focusing strategy, an ultrasensitive DNA assay was developed for quantitation of calf thymus dsDNA (from 0.02 to 2.14 pM). By the use of an excitation laser power as low as 1 mW, the detection limits of calf thymus dsDNA (3.5 kb) are 7.9 fM in concentration and 2.4×10^?22 mol (150 molecules) in mass. We further demonstrate that the non‐gel sieving CE‐LIF analysis of DNA fragments can be enhanced by the same strategy. Since the presented strategy can be applied to uncoated and coated capillaries and does not require special device, it is also reasonable to extend to the applications in chip‐based CE DNA analysis.     

Relaxation dynamics in the excited states of a ketocyanine dye probed by femtosecond transient absorption spectroscopy

Relaxation dynamics of the excited singlet states of 2,5-bis-(N-methyl-N-1,3-propdienylaniline)-cyclopentanone (MPAC), a ketocyanine dye, have been investigated using steady-state absorption and emission as well as femtosecond time-resolved absorption spectroscopic techniques. Following photoexcitation using 400 nm light, the molecule is excited to the S₂ state, which is fluorescent in rigid matrices at 77 K. S₂ state is nearly non-fluorescent in solution and has a very short lifetime (0.5 ± 0.2 ps). In polar aprotic solvents, the S₁ state follows a complex multi-exponential relaxation dynamics consisting of torsional motion of the donor groups, solvent re-organization as well as photoisomerization processes. However, in alcoholic solvents, solvent re-organization via intermolecular hydrogen-bonding interaction is the only relaxation process observed in the S₁ state. In trifluoroethanol, a strong hydrogen bonding solvent, conversion of the non-hydrogen-bonded form, which is formed following photoexcitation, to the hydrogen-bonded complex has been clearly evident in the relaxation process of the S₁ state.     

Application of the Organic Photosensitizers Bearing Two Carboxylic Acid Groups to Dye‐Sensitized Solar Cells

Three electron donor‐?? bridge‐electron acceptor (D‐π‐A) organic dyes bearing two carboxylic acid groups were applied to dye‐sensitized solar cells (DSSC) as sensitizers, in which one triphenylamine or modified triphenylamine and two rhodanine‐3‐acetic acid fragments act as D and A, respectively. It was found that the introduction of t‐butyl or methoxy group in the triphenylamine subunit could lead to more efficient photoinduced intramolecular charge transfer, thus improving the overall photoelectric conversion efficiency of the resultant DSSC. Under global AM 1.5 solar irradiation (73 mW·cm^?2), the dye molecule based on methoxy‐substituted triphenylamine achieved the best photovoltaic performance: a short circuit photocurrent density (J_sc) of 12.63 mA·cm^?2, an open circuit voltage (V_oc) of 0.55 V, a fill factor (FF) of 0.62, corresponding to an overall efficiency (η) of 5.9%.