Rodrigues, J. A. O.Oliveira Neto, J. G.Santos, C. C.Nogueira, C. E. S....
12页
查看更多>>摘要：Tris(glycinato)chromium(III) monohydrate [Cr(C2H4NO2)(3)center dot H2O] crystals were grown through the slow solvent evaporation method. The crystals were studied by Fourier transform infrared (FTIR) and Raman spectroscopy at room temperature. The assignments of vibration modes were performed using the Density Functional Theory (DFT). Thermal analyses (TGA, DTA, and DSC), X-ray diffraction (XRD), and Raman were used to study the phase changes on the crystals under high- and low-temperature conditions. Temperature-dependent XRPD measurements were carried out in the interval of 473-12 K. Several changes were observed in the patterns, like the appearance of new peaks and the disappearance of peaks occurring within 373-393 K due to water loss. In addition, the Raman measurements were performed in the 423-10 K interval. Several changes on the inter and intramolecular vibration bands during the cooling, such as decreasing bands' intensities, the appearance of vibration modes, and discontinuities on the modes' behavior, were observed. These spectral modifications occurred at about 370 K and within 120-220 K, thus, confirming that the crystals undergo two phase changes, one being structural and the other one conformational, respectively, at high- temperature and low-temperature conditions. Finally, thermal investigations corroborated the structural and vibrational results under high temperatures. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this paper, one-photon absorption (OPA) spectrum and two-photon absorption (TPA) spectrum and its electronic excitation, charge transfer, partial density of states (PDOS) and magnetic induction current density of zigzag edge twisted bilayer graphene quantum dots (Z-TwBLG-QDs) with different twisted angles which were divide into two pattern of Moire superlatrate (MS) are qualitativly and quantitativly analyed by using density functional theory (DFT), excited state wave function, single electron approximation, and gauge-invariant atomic orbital (GIAO) method. The inter-layer local excitation in the electronic transition and intra-layer charge transfer dominated by MS and anti-symmetric electron-hole pair density induced by PDOS are discussed. The twisted angle is decisive to the absorption spectrum, large twisted angle will lead to the red shift of the absorption spectrum. The two-photon transition shows that the twisted angle can regulate the TPA cross section and the boundary effect of Z-TwBLG-QDs in a specific wavelength range. The edge effect of two-step transition can be enhanced by MS with specific twisted angles. The physical mechanism of twisted angle regulating electron transition behavior is revealed by magnetic induction current density analysis. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The study of secondary structure is essential for understanding peptides and proteins. Here, we measured the terahertz (THz) spectra of gamma-polyglutamic acid (gamma-PGA) dominated by alpha-helix and random coil (RC) respectively. The alpha-helix has two absorption peaks in the THz region, but no absorption peak is observed in the RC conformation. We believe this is because the hydrogen bonding effect leads to a higher orientation in the helix-dominated gamma-PGA. At lower pH, the absorption intensity of gamma-PGA increases with the induction time. Similar changes were obtained in the Fourier infrared spectroscopy (FTIR). Through the correlation analysis of THz and IR spectroscopy, it is found that the characteristic peak at 1.2 THz can be used as a sensitive indicator of the intermediate conformation of the alpha-helical structure. In addition, the transformation of alpha-helix-RC conformation is related to the peak intensity at 1.99 THz (R-2 = 0.991), which preliminarily indicates that terahertz time-domain spectroscopy (THz-TDS) has the potential to become a new effective method for characterizing and evaluating secondary structure. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Metallohydrogels and lanthanide (Ln) fluorescent materials have gained much attention recently. In this study, we designed and synthesized a facile gelator of a phenylalanine-based derivative containing an indazole group (namely IZF). It was found that IZF can self-assemble to form hydrogel at pH <= 7. Meanwhile, IZF and Tb3+/Eu3+ can co-assemble to generate IZF-Tb and IZF-Eu metallohydrogels with green and red fluorescence, respectively, at pH 8-11, with excellent multi-stimuli responsiveness. The bimetallic hydrogels of IZF-Tb/Eu exhibit different colors under UV light by adjusting the ratio of Tb3+ and Eu3+. Moreover, white light emission was achieved with IZF-Tb/Eu bimetallic gels through doping carbon dots (CDs) by tailoring the stoichiometric ratio of Ln-complex and CDs. Remarkably, IZF-Tb and IZF-Eu could be used as fluorescent inks with excellent stability. This study indicates that the amino acid derivative-based Ln-metallohydrogels are excellent candidates for constructing information storage and multiple anti-counterfeiting materials. (C) 2022 Elsevier B.V. All rights reserved.
Zahid, MuhammadKhan, Muhammad FarooqIsmail, MuhammadWang Xiangke...
10页
查看更多>>摘要：Herein, an economical, analytical and sensitive method was established for the fluorometric determination of urea using freshly prepared silver nanoparticles (Ag-NPs) in real urine samples. The standard addition and second-order derivative methods were selected for the ongoing research work to eliminate the possible effect of interferences in a real environment. In this work, Ag-NPs were prepared by reducing silver nitrate salt in the presence of 1,3-di-(1H-imidazole-1-yl) -2-propanol (DIPO) in an aqueous medium. Urea in the urine samples was successfully determined through the complexation of Ag-NPs with urea molecules. The results revealed high percent recovery with +/- RSD of urea in the three different urine samples, where percent recoveries by spectrofluorometric standard addition were 99.77 +/- 3.4, 100.24 +/- 5. 1, 100.93 +/- 2.8 and that is by the spectrofluorometric second-order derivative method were 103.57 +/- 2.4, 101.8 +/- 1.3, 98 +/- 3.2, respectively. The successful application of these analytical methods in the spectrofluorometric determination of urea in urine samples can accumulate further addition in the effects and possible role of Ag-NPs in the determination of biological molecules in biological and nonbiological samples in the scientific as well as clinical fields. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Though a number of on-off or off-on fluorescent probes have been developed for the detection of thiophenol by using its unique recognition groups, such as 2, 4-dinitrophenyl ether, 2, 4-dinitrophenyl sulfonamide, and 2, 4-dinitrophenyl sulfonate, up to now, there are few probes that can detect thiophenol by the proportional fluorescence signal. We developed a ratiometric fluorescent probe with coumarin pyridine derivative as fluorophore and 2, 4-dinitrophenyl ether moiety as the sensing unit which could be used to detect thiophenol derivatives by the aromatic nucleophilic substitution reaction. This probe (CPBPN) displayed significant change in fluorescence ratio (256 fold) to result in a more reliable analysis by self-calibration and a relatively low detection limit of 24 nM toward 4-methylthiophenol (MTP) within 30 min to achieve more sensitivity. Besides, the probe was also applied to detect the presence of thiophenol derivatives in actual water samples and fluorescence imaging in living cells. The present work is of great importance for monitoring environmental pollutants and studying their biological function. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The carbon nanomaterial based fluorescent probes have been widely applied in biological imaging. In the current research, we propose an interesting strategy for selective sensing of hypochlorite (ClO-) by a water-soluble and highly fluorescent nanosensor based on the N-doped carbon quantum dots (CDs) which was fabricated by a facile and environmental friendly hydrothermal approach from polyvinyl pyrrolidone, L-arginine and tryptophan. The structural characteristics of the probe were measured by multitudinous methods which proved the nanometer spherical structure of the probe and the successfully N-doping. Fluorescent investigation demonstrated that the probe is not only highly stable under interferences of pH, ionic strength, and irradiation, but also significantly selective toward ClO- amongst a variety of attractive bioactive species through the fluorescent quenching process which was correlative with the concentration of ClO- and linearly in the range of 0.1-50 mu mol.L-1 with the sensitivity of 0.03 mu mol.L-1. The probe can also be further illustrated in a prospective application for determination of ClO- in environmental water through both solution response and filer paper sensing. Moreover, the positive biocompatibility and ignorable cytotoxicity made the probe a promising effective agent for detection and visualizing ClO- in living cells which can facilitate the understanding the oxidative stress from the overexpressing ClO-. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In view of the ever-growing demand for efficient NIR fluorophores for biomedical applications, we herein report the synthesis and properties of four unsymmetrical aza-BODIPYs exhibiting NIR fluorescence. Highly desirable photophysical and photochemical properties were induced in these molecules due to the presence of both strongly electron-withdrawing p-nitrophenyl rings (p-NO2Ph-) and mildly electron-donating p-methoxyphenyl rings (p-MeOPh-) within the aza-BODIPY core. In particular, upon excitation with lambda(abs) the unsymmetrical aza-BODIPYs studied exhibited NIR emission with lambda(f) ranging from 699 nm to 718 nm in toluene. The fluorescence quantum yields (Phi(f)), depending on the substitution pattern, ranged from Phi(f) = 0.49 to Phi(f) = 0.22 and the fluorescence lifetimes ranged from tau(f) = 1.90 ns to tau(f) = 3.59 ns. Aza-BODIPY with electron-donating substituent at 3 position and electron-withdrawing substituent at 5 position was identified as cell permeable, NIR emitting fluorophore suitable for bioimaging. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Polymethine dyes (PMD) have proved to be excellent candidates in the biomedical field for potential applications in both diagnostic and therapeutic. However, PMD application in biomedicine is hindered by their poor solubility and stability in physiological conditions. Therefore, the incorporation of these dyes in nanosystems could be important to prevent the formation of dye aggregates in aqueous environment and to protect their photophysical characteristics. In the present work, two PMD based on the benzoindolenine ring (bromine benzo-cyanine-C4 and bromine benzo-squaraine-C4) were incorporated into Solid Lipid Nanoparticles (SLN) to solubilize and stabilize them in aqueous solutions. Obtained SLN showed a high incorporation efficiency for both PMD (approximate to 90%) and not only preserved their spectroscopic properties in the NIR region even under physiological conditions but also improved them. Viability assays showed good biocompatibility of both empty and loaded nanocarriers while the cellular uptake and intracellular localization showed the effective internalization in MCF-7 cells, with a partial mitochondrial localization for CY-SLN. Moreover, in vitro phototoxicity assay showed that cyanine loaded-SLN (CY-SLN) is more photoactive than the free dye. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Considering the scarcity of hydrogen sulfide (H2S) probes with subcellular organelle targeting, especially probes with near-infrared (NIR) emission wavelengths fluorophores, our group has been working to overcome this problem and looking forward to providing potential practical tools for exploring the relationship between the physiology and pathology of H2S at subcellular level. In this paper, a novel colorimetric and NIR fluorescent probe SHCy-H2S for the specific detection of H2S in lysosome over other biological thiols was designed and synthesized. The xanthene-benzothiozolium fluorophore was chosen to provide fluorescence emission maxima over 735 nm, and 2,4-dinitrophenyl group was chosen as fluorescence quenching group and specific H2S response site. Impressively, SHCy-H2S exhibited high selectivity, fast response and detection limit as low as 0.116 lM for H2S, marked obvious color changes in naked-eye and fluorescence. Specially, SHCy-H2S was capable of specifically imaging endogenous lysosomal hydrogen sulfide, providing a potential tool for exploring the function of H2S at subcellular level. (C) 2022 Elsevier B.V. All rights reserved.
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