Fluorescence Emission Spectra Research Articles

Optical and dielectric features of PVC/ZnCo2O4/MWCNTs/TBAI polymers for optoelectronic and energy storage applications

Zinc cobalt oxide is considered a highly desirable substance for use in a wide range of applications, particularly supercapacitors. In this study, polyvinyl chloride/zinc cobalt oxide/multi-walled carbon nanotubes/x wt % tetrabutylammonium iodide (PVC/ZnCo2O4/MWCNTs/x wt % TBAI) composite polymers were fabricated using casting and hydrothermal approaches. The resulting composites were then analyzed to determine their structure, optical properties, and dielectric characteristics. The structure of ZnCo2O4 and PVC/ZnCo2O4/MWCNTs/x wt.% TBAI were studied using the X-ray diffraction technique. The morphologies of doped polymer were investigated using SEM technique. The impact of ZnCo2O4/MWCNTs/x wt.% TBAI filler samples on the linear and nonlinear optical properties of PVC polymer has been analyzed through UV diffused reflectance measurements. The doped samples could serve as effective shields against ultraviolet radiation across different wavelengths (UVA, UVB, UVC) and a highly effective material for absorbing solar energy in solar cells. The lowest optical energy gap values are attained (3.77, 3.03) and (3.32, 2.55) eV for the direct and indirect optical band gaps in PVC/ZnCo2O4/MWCNTs/3 wt% TBAI polymer, respectively. The largest refractive index value at 600 nm was observed in the doped polymer with 6 wt% TBAI. The fluorescence emission spectra and dielectric properties of the PVC/ZnCo2O4/MWCNTs/x wt.% TBAI polymers are also studied. The highest electrical dielectric constant was achieved in the ZnCo2O4/MWCNTs/9 wt% TBAI polymer. It follows that the PVC/ZnCo2O4/MWCNTs/x wt % TBAI has the ability to open up new possibilities for use in optoelectronic devices.

A ratiometric fluorescent probe for cysteine and glutathione differentiation and its application for cysteine detection in foods

Cysteine (Cys) and glutathione (GSH) are crucial biothiols implicated in cellular redox balance, necessitating accurate detection methods. Herein, we developed a novel fluorescent probe based on the fluorescent dye pyronin (PYR), capable of monitoring both Cys-and GSH using ratiometric fluorescence signals. The probe, named PYR-CG, where "C" stands for Cys-and "G" stands for GSH, demonstrates selective detection capabilities for Cys-and GSH. UV absorption and fluorescence emission spectra changes revealed distinct shifts upon interaction with Cys-and GSH. Theoretical and experimental studies validated PYR-CG's responsiveness to Cys-and GSH, elucidating its mechanism as a ratiometric probe. Notably, PYR-CG exhibited rapid response kinetics for Cys-and GSH, with low detection limits of 88 nM and 164 nM, respectively. Importantly, PYR-CG demonstrated exceptional selectivity for Cys-and GSH over interfering analytes. Screening of molecules with similar structures to Cys-further affirmed PYR-CG's specificity, particularly towards N-terminal Cys-in peptides. Furthermore, recovery experiments underscored PYR-CG's reliability for quantitative Cys-detection in complex food samples. Our findings highlight the innovative design and practical applicability of PYR-CG, offering a valuable tool for sensitive and selective detection of Cys-in diverse biological and food samples.

Fluorescence spectra as an indicator of the influence of environmental conditions on fruit trees

Molecular fluorescence spectra determine possible structural changes of these molecules and provide data (by comparing them with absorption ones) on the efficiency of solar energy utilization. Fluorescence emission spectra provide information on the functionality of the photosynthetic apparatus by means of two bands red F690 and beyond red F735. The objective of the study is to highlight possible changes in the organization and operation of the photosynthetic apparatus, induced by different radiations, in the leaves, for a variety of pear (Santa Maria), based on the characteristics of the two bands of emitted fluorescence. The Santa Maria variety was studied in the period of June.

Probing noncovalent binding, spectroscopic characteristics and antiproliferative behavior of inclusion complex between quinoline and para-sulfonatothiacalix[4]arene

The inclusion complex between bowl-shaped para-sulfonatothiacalix[4]arene (TSCX4) macrocycle and quinoline has been studied with a unison of UV–visible, infra-red, flourescence emission and 1H nuclear magnetic resonance (NMR) and 2D nuclear overhauser effect spectroscopy (NOESY), high resolution mass spectrometry (HRMS) experiments. Both 1H NMR titration and HRMS experiments point to 1:1 stoichiometry for the water soluble Q⊂TSCX4 complex. The electronic structure of the inclusion complex obtained from density functional theory (DFT) showed a partial encapsulation of quinoline guest, which is held within the host cavity by C–H---π, π---π and hydrogen bonding interactions. The fluorescence emission spectra upon complexation display marginal blue shift of the 411 nm band in TSCX4. Moreover, the binding constant (7.1 × 103 M−1) determined from fluoresence emission experiments underline the effective host–guest binding in the complex, which was corroborated through frequency up-shift (‘blue shift’) of characteristic Ar-OH (3433 cm−1) and SO3- vibrations (1141 cm−1 and 1037 cm−1) in the measured infrared spectra of TSCX4. The antiproliferative activitities of the Q⊂TSCX4 complex against HeLA, MDA-MB-231and N2a cells are presented. The Q⊂TSCX4 complex has been shown to be efficient against N2a (neuroblastoma) cell line.

New 3-D Fluorescence Spectral Indices for Multiple Pigment Inversions of Plant Leaves via 3-D Fluorescence Spectra

High-sensitivity fluorescence monitoring has been widely used in agriculture and environmental science. However, the active fluorescence detection information of leaf segments mainly focuses on total chlorophyll, and the fluorescence information of chlorophyll a, chlorophyll b, and some other pigments has not been explored. This only considers the fluorescence spectrum characteristics at a single wavelength or the fluorescence integral from a range of wavelength regions and does not completely consider the linkage relation between the excitation, emission, and interference information. In this paper, the three-dimensional fluorescence spectrum, containing the excitation and emission fluorescence spectra, and the corresponding multiple pigment characteristics from the upgraded LOPEX_ZJU database were collected. The linkages of excitation and emission of the three-dimensional fluorescence spectra of these pigments were analyzed for the newly built multiple pigment 3-D fluorescence spectral indices (3-D FSIs), including those of chlorophyll a, chlorophyll b, carotenoid, anthocyanin, and flavonoid 3-D FSIs. Then, these pigment inversion models were established and validated. The results show that the 3-D FSIs performances for the photosynthetic pigment content inversion (including chlorophyll a and b, and carotenoids) were much better than those for the photo-protective pigments (including anthocyanins and flavonoids) from the 3-D fluorescence spectra of these plant leaves. Here, the 3-D fluorescence normalization index (FNI ((F430,690-F430,763)/(F430,690+F430,763))) for the chlorophyll a inversion model has a high accuracy, the RMSE is 2.96 μg/cm2, and the 3-D fluorescence reciprocal difference index (FRI (F650,704/F650,668) for the chlorophyll b model has an encouraging RMSE (2.01 μg/cm2). The RMSE of the 3-D fluorescence ratio index (FRI (F500,748/F500,717)) for the carotenoid inversion is 3.77 μg/cm2 RMSE. Only FRI (F370,615/F370,438) was selected for the modeling and validating evaluation of the leaf Flas content inversion, but the evaluation metrics were not good, with an RMSE (151.13 μg/cm2). For Ants, although there was a 3-D FSI (FRDI (1/F540,679-1/F540,557)), and its evaluation metrics, with an RMSE (2.8 μg/cm2), were at or over 0.05 level, the validating evaluation metric VC (98.3577%) was not encouraging. These results showed that fluorescence, as a nondestructive and efficient detection method, could determine the contents of chlorophyll a, chlorophyll b, and carotenoid in plant leaves, providing a new method to detect plant information. It can also provide a potential chance for the fluorescence images of fine photo-protective pigments, especially chlorophyll a and b, using the special active fluorescence excitation light source and a few fluorescence imaging channels from the optimal FSIs.

A pyridine naphthalene conjugate: ESIPT based molecular chemosensor for Al3+ ions and sequential detection of H2PO4- and applications in milk, water samples and bio-imaging

A fluorescent probe (HL) with an "off-on-off" feature was created to identify Al3+ ions in aqueous solutions. The probe can identify Al3+ ions while other metal ions are present, and it is made to be straightforward to use. The probe was built utilizing a Schiff-base chemosensor, 1-[(pyridin-2-ylimino)] naphthalene-2-ol (HL), and a variety of spectroscopic methods were employed to describe it. Probe HL's sensing ability was assessed in a 1:1 volumetric ratio THF/H2O medium, and to establish the binding with Al3+ ions, several spectroscopic methods such as 1H NMR titration analysis, ESI-MS technique including DFT analysis were used. The probe HL showed notable alterations in fluorescence emission spectra during the detection of Al3+ and H2PO4- in the presence of other competing ions. The value of the association constant and the detection limit for Al3+ and H2PO4- were found to be 8.51×104 M-1 and 5.5×102 M-1, respectively. Besides, its applications as tests using milk and water samples successfully identified Al3+ ions in the presence of the probe HL. Additionally, probe HL was successfully examined in E.Coli pathogen for the sensing of Al3+ and H2PO4- ions

Modulation of micro-structural, opto-electronic and photo-induced fluorescence properties in sol-gel derived Pb1-xZnxO nanoparticles through the analytical study of vacancy-type defects

In the present work, the doping effect of Zn2+ ion (varying doping concentrations in the range of 0 %–30 %) on PbO nanoparticles (NPs) has been investigated proficiently. This study aims at in-depth analysis of the structure-property relationships of the sol-gel derived Zn doped PbO (Pb1-xZnxO) NPs, especially the vacancy evolved properties and the luminescence properties. The X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), field emission scanning electron microscopy (FESEM) and Fourier-transform infrared (FT-IR) spectroscopic characterization analyses justified the nanocrystallinity of the Pb1-xZnxO powdered NPs while the mean crystallite sizes were located in between 12 and 36 nm range. Williamson – Hall (W – H) method revealed a monotonous increase of the lattice strain which is compatible with the decrease of NPs’ crystallite size by increase in the Zn2+ doping level. The replacement of Pb2+ ions with the Zn2+ ions caused the reduction of crystallite size by the higher Zn2+ doping level. Prominent peaks of Zn, Pb and O elements are noticed in energy dispersive X-ray spectroscopic (EDS) characterization. The elemental distributions of the chemicals present in the NPs were explored by the elemental mapping analysis. The optical absorption (OA) analysis indicated that the energy band gap (Eg) can be estimated to be 2.21, 2.36, 2.55 and 2.70 eV for 0, 10, 20 & 30 % Zn doped PbO NPs, respectively. The positron annihilation lifetime (PAL) spectroscopic studies evidenced the presence of vacancy type defects within the NPs and an increase in defect concentrations has been observed by the increase in Zn concentrations. The photo-induced fluorescence (FL) emission spectra exhibited three luminescence peaks around the wavelengths 430 nm, 490 nm and 522 nm for all the NPs. The observations suggested the possibility of tailoring the characteristics of the synthesized NPs for practical applications in the field of optoelectronics.

Biological and equilibrium studies of Co(II), Cu(II), Zn(II), and Cd(II) complexes of 1‐formyl‐3‐semicarbazide: Docking studies

1‐Formyl‐3‐semicarbazide (FSC, HL) and its metal complexes with Co(II), Cu(II), Zn(II), and Cd(II) ions have been synthesized and characterized by elemental analysis, liquid chromatography‐mass spectrometry (LC–MS), infrared (IR), electronic, nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy, thermogravimetric analysis (TGA), magnetic susceptibility, and conductivity measurements. The chelates are non‐electrolytic in nature with distorted octahedral geometry. The kinetic and thermodynamic properties were calculated using the Coats–Redfern relation results in positive enthalpy change values and negative entropy change values. The equilibrium studies of FSC with Co(II), Zn(II), and Cd(II) ion have been carried out by potentiometric pH titrations in 70% v/v DMF‐water medium at 303 K and 0.1 M (KNO3) ionic strength. The study revealed that FSC is monobasic acid with pKa value of 8.84. The stability constants suggested the formation of 1:1 Co(II)‐FSC complex, and Zn(II)‐FSC and Cd(II)‐FSC systems revealed the formation of both 1:1 and 1:2 complexes in the solution. DNA binding studies for the metal chelates have been carried out using electronic absorption spectra, fluorescence emission spectra, and viscosity measurements revealing groove binding for Co(II), and Zn(II) complexes, and intercalation mode of binding for Cu(II)‐FSC complex with CT‐DNA. The Kb values from absorption studies are Co(II)‐FSC = 0.9990 × 102, Cu(II)‐FSC = 2.433 × 104, and Zn(II)‐FSC = 8.277 × 102 M−1, and the KSV values from the competitive fluorescence emission studies are Co(II)‐FSC = 0.19212 and Cu(II)‐FSC = 0.11482 M−1. Molecular docking carried out for both ligand and its Co(II) and Zn(II) complexes also revealed groove mode of binding, and Cu(II) complex showed intercalative mode of binding. The inhibition constants for HL, Co(II), Cu(II), and Zn(II) are 1460, 0.478, 0.122, and 0.194 μM, respectively. The antimicrobial activity has been studied using agar disk diffusion method against Escherichia coli and Bacillus subtilis. FSC has been found to be more active against gram +ve and gram –ve bacteria than its metal chelates.

Computational Hyperspectral Microflow Cytometry.

Miniaturized flow cytometry has significant potential for portable applications, such as cell-based diagnostics and the monitoring of therapeutic cell manufacturing, however, the performance of current techniques is often limited by the inability to resolve spectrally-overlapping fluorescence labels. Here, the study presents a computational hyperspectral microflow cytometer (CHC) that enables accurate discrimination of spectrally-overlapping fluorophores labeling single cells. CHC employs a dispersive optical element and an optimization algorithm to detect the full fluorescence emission spectrum from flowing cells, with a high spectral resolution of ≈3nm in the range from 450 to 650nm. CHC also includes a dedicated microfluidic device that ensures in-focus imaging through viscoelastic sheathless focusing, thereby enhancing the accuracy and reliability of microflow cytometry analysis. The potential of CHC for analyzing T lymphocyte subpopulations and monitoring changes in cell composition during T cell expansion is demonstrated. Overall, CHC represents a major breakthrough in microflow cytometry and can facilitate its use for immune cell monitoring.

Cyclotriphosphazene‐Based Photocatalysts containing Orthogonal BODIPY Moieties for Chemical Transformations

AbstractMolecular organic photocatalysts developed for use in chemical transformation reactions have gained momentum in recent years. In this study, six new triplet photosensitizers were prepared to determine their photocatalyst capabilities and chemical transformation abilities. The chemical structures of the synthesized orthogonal BODIPYs and their cyclotriphosphazene derivatives were analyzed and then their photophysical characteristics including the UV‐Vis absorption spectra, fluorescence emission spectra, fluorescence quantum yields, were investigated. The quantitative singlet oxygen formation was determined by chemical trapping using DPBF (diphenylisobenzofuran). In particular, cyclotriphosphazene derivative 12 having three BODIPY moieties showed efficient singlet oxygen production with high photostability and good molar extinction coefficient. The photo‐oxidation ratio constant of 1,5‐dihydroxynaphthalene (DHN) was calculated as 28.7×10−3 min−1 for compound 12 and at the end of 22.5 min., DHN converted to juglone with 100 % efficiency. In addition, the ability of the compounds to convert 1,3‐cyclohexadiene into peroxides in the presence of molecular oxygen and light was investigated and the conversion efficiency was determined by NMR technique. All compounds have been presented as photocatalysts for use in different synthetic photochemistry applications.

The quantification of southern corn leaf blight disease using deep UV fluorescence spectroscopy and autoencoder anomaly detection techniques.

Southern leaf blight (SLB) is a foliar disease caused by the fungus Cochliobolus heterostrophus infecting maize plants in humid, warm weather conditions. SLB causes production losses to corn producers in different regions of the world such as Latin America, Europe, India, and Africa. In this paper, we demonstrate a non-destructive method to quantify the signs of fungal infection in SLB-infected corn plants using a deep UV (DUV) fluorescence spectrometer, with a 248.6 nm excitation wavelength, to acquire the emission spectra of healthy and SLB-infected corn leaves. Fluorescence emission spectra of healthy and diseased leaves were used to train an Autoencoder (AE) anomaly detection algorithm-an unsupervised machine learning model-to quantify the phenotype associated with SLB-infected leaves. For all samples, the signature of corn leaves consisted of two prominent peaks around 450 nm and 325 nm. However, SLB-infected leaves showed a higher response at 325 nm compared to healthy leaves, which was correlated to the presence of C. heterostrophus based on disease severity ratings from Visual Scores (VS). Specifically, we observed a linear inverse relationship between the AE error and the VS (R2 = 0.94 and RMSE = 0.935). With improved hardware, this method may enable improved quantification of SLB infection versus visual scoring based on e.g., fungal spore concentration per unit area and spatial localization.

Rigid symmetric Rhodamine fluorescent dyes as fast selective detection of aluminum and iron ions applied to cell imaging

Fluorescent probe molecules have the advantages of good selectivity, high sensitivity, and easy operation, which have attracted much attention. In this paper, a novel symmetric rhodamine fluorescent probe with structural rigidity was synthesized by a simple reaction using rhodamine 6G as raw material. And it was characterized by NMR and electrospray spray mass spectrometry. Single crystal was prepared by solvent evaporation method, which was the first single crystal of the compound reported domestically and internationally. Special spiral ring structures were observed inside the crystal. Among different competing cations, the probe exhibited high selectivity and good sensitivity towards Al3+ and Fe3+ metal ions. The limits of detection were 0.76 nM and 0.49 nM, respectively. In the presence of Al3+ and Fe3+, the solution changed from colorless to pink. At the same time, there was a significant shift in the UV–vis spectrum and fluorescence emission spectrum. The UV–vis absorption peak appeared at 530 nm, while the emission at 556 nm was turned on. In addition, biological experiments have shown that the RP probe has good membrane permeability and has the potential to detect Al3+ and Fe3+ in Hela cells.

Experimental Optimization, Design Synthesis, and Up-Conversion Luminescence Properties of Y4GeO8: Er3+/Yb3+ Red Phosphors

The Er3+/Yb3+ co-doped Y4GeO8 crystal powders were successfully synthesized us-ing a high-temperature solid-phase method. The crystal structure of the obtained phosphors was confirmed to be pure Y4GeO8 through X-ray diffraction (XRD) analysis. A regression equation correlating Er3+/Yb3+ doping concentrations with luminescent intensity was estab-lished based on the optimized theoretical model derived from experimental design. The op-timal concentrations of Er3+ and Yb3+ under 980 nm laser excitation were determined as 7.41% and 21.34%, respectively, while under 1550 nm laser excitation, the concentrations were 2.66% and 17.42%, respectively. The fluorescence emission spectra of the up-conver-sion samples were measured, revealing intense green and red emissions with peaks at 542, 546, and 654 nm under 980 nm excitation, and peaks at 546, 557, and 663 nm under 1550 nm excitation. These peaks correspond to transitions from 2H11/2 to 4I15/2, 4S3/2 to 4I15/2, and 4F9/2 to 4I15/2 energy levels. The relationship between up-conversion luminescence and laser op-erating current for the optimal samples under 980 nm and 1550 nm was investigated, uncov-ering that up-conversion luminescence occurs through both two-photon and three-photon processes. A detailed analysis and discussion of the up-conversion luminescence mecha-nisms were conducted. Furthermore, the relationship between up-conversion fluorescence and temperature for the optimal samples was studied, revealing excellent temperature-sens-ing characteristics under 980 nm and 1550 nm laser excitations. The calculated illumination region coordinates for the optimal samples under 980 nm and 1550 nm wavelength excitations were (0.5558, 0.4362) and (0.5256, 0.4687), respectively. The research highlights the potential of rare-earth ion-doped up-conversion luminescent materials for diverse anti-coun-terfeiting applications. In particular, the Y4GeO8: Yb3+/Er3+ phosphors, incorporating a dual-excitation mechanism, enhance the security of anticounterfeiting strategies in multifaceted scenarios. The study underscores the promising developments in this field.

Green synthesis of fluorescent carbon dots from ascorbic acid and their application in sensing and biological imaging

A simple, highly efficient, and environmentally friendly one-step method has been developed to synthesize fluorescent carbon dots (CDs) with the assistance of hydrogen peroxide (H2O2). Here H2O2 acts as a green accelerator to promote the preparation of CDs, while temperature plays a critical role in controlling the entire synthesis process. The prepared CDs demonstrate monodispersion, with an average diameter of ∼6.8 nm, superior stability, and excitation-dependent photoluminescent (PL) behavior. The PL mechanism of the CDs was investigated using time-resolved PL decay, revealing that the PL originates from both the defect state and the intrinsic state of the CDs. Furthermore, the CDs show significant promise as pH sensors and versatile nanothermometry devices, owing to their remarkable sensitivity to both pH and temperature, as demonstrated by the pronounced dependence of their steady-state fluorescence emission spectra. It’s worth noting that temperature and pH sensors present significant reversibility, sensitivity, and linearity. More importantly, the CDs display low cytotoxicity, good biocompatibility, and the ability to enter human breast cancer Bcap-37 cells, making them highly suitable candidates for cellular imaging and labeling.

PHire: A Novel Red Intracellular pH Sensor

Maintaining pH is critical for proper cellular and organ function. To measure intracellular pH, we made a novel genetically encoded protein, pHire, that increases red fluorescence with increasing pH. Thus, pHire allows for the coupling of multiple fluorescent tags without spectral overlap. We have expressed pHire in mammalian epithelial cells, Drosophila, and mice. In this study, our goal was to characterize pHire’s spectral properties by expression in human cells (HEK293) and in E.coli. To biophysically characterize pHire, we made a maltose binding protein (MBP)-pHire fusion protein to purify from E.coli. Pelleting individual colony growths revealed pink bacterial pellets which fluoresced with mCherry filters. Rather than purifying the MBP-pHire protein, equal volumes of bacteria were permeabilized with nigericin and high K+ solution for pH 5 to 9. These aliquots were then used to gather the fluorescence excitation and emission spectra of pHire, allowing us to determine the excitation and emission peaks of pHire as a function of pH. Our results showed peaks at Ex579 nm and Em611 nm, or roughly mCherry. Pelleted bacteria could also be fixed in perfusion chambers, revealing the same calibration curve as in mammalian cells and flies. Next, stable HEK293-pHire cells were selected to assay acid-base transport using NH4Cl or CO2/HCO3− in perfusion experiments. These HEK-pHire cells have less fluorescence than MBP-pHire bacteria but show the same Ex/Em peaks. However, an in-frame ATG 5’ to pHire in a mouse (adding 23 amino acids), removed pHire pH-dependence and decreased bacterial fluorescent output. Together these results indicate that pHire is biophysically similar in cells tested but that unstructured N-terminal additions block pH-responses. Funding: R25-DK101405, R21-DK129897. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

First-principles study on the modulation mechanism of solvent effect on the fluorescence emission of carbon dots

Solvent effect is one of the effective pathways to regulate the fluorescence emission spectra of carbon dots (CDs). In this work, the solvent effect on fluorescence emission of CDs with functional groups has been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Solvation model based on density (SMD) and microsolvent-SMD models have been employed to simulate the solvent effects. The electron donating or withdrawing ability of the surface functional groups of CDs, the polarity of the solvent, and the interaction between solvent molecules and CDs were analyzed. The results indicate that microsolvent-SMD model comprehensively considers the solvent polarity and the interaction between solvent molecules and functional groups, which is more advantageous to revealing the physical nature of solvent molecules participating in fluorescence emission, resulting in the calculated fluorescence spectra closer to experimental results. The hydrogen bonds can modulate the fluorescence spectra of CDs more significantly than the solvent polarity, when the CDs are primarily characterized by n-π* transitions, hydrogen bonding induces a blue shift in the fluorescence spectrum, whereas when the CDs mainly undergo π-π* transitions, hydrogen bonding causes a red shift in the spectrum. This work provides theoretical guidance to exploit the solvent effect to achieve effective modulation of the fluorescence properties of CDs.

Design and synthesis of multi-coloured electrochromic and electrofluorochromic asymmetric materials by adjusting the central potential of the compounds

Carbazole and triphenylamine derivatives have become popular research topics in the field of electrochromism and electrofluorochromic due to their excellent reversible oxidative activity, reversible colour change and reversible fluorescence change during electrochemical processes. Four asymmetric carbazole-triphenylamine derivatives 6a-d were designed and synthesized. Both ultraviolet absorption (UV) spectra and fluorescence emission (PL) spectra changed with the change in voltage applied to all compounds. These compounds were fabricated into electrochromic and electrofluorochromic devices, and these devices exhibited excellent cycling stability (cycling stability remains above 95% after 11000 s), short switching time (1.1 s ∼ 1.6 s), high PL contrast (146 ∼ 172), and high colour contrast (47.2% ∼ 50.6%). All the samples fluoresced off in the oxidised state and exhibited alternating yellow-green characteristics, and fluoresced on in the reduced state while exhibiting a highly transparent and colourless state. The experimental results indicated that these materials are expected to be used for the preparation of wearable devices and transparent displays. The research demonstrated that rich color changes can be achieved by adjusting the electrochemical properties of dual redox centered materials.

A novel near-infrared fluorescent probe for real-time monitoring of leucine aminopeptidase activity and metastatic tumor progression

This article discusses the importance of early tumor detection, particularly in liver cancer, and the role of leucine aminopeptidase (LAP) as a potential marker for liver cancer diagnosis and prognosis assessment. The article highlights the limitations of current tumor markers and the need for new markers and multi-marker approaches to improve accuracy. The authors introduce a novel near-infrared fluorescent probe, NTAP, designed for LAP detection. They describe the synthesis of the probe and evaluate its spectral properties, including the LOD was 0.0038 U/mL, and QY was 0.32 %. The kinetic properties of NTAP, such as the relationship between LAP concentration (0–0.08 U/mL), reaction time (3 min), and fluorescence excitation spectra (475 nm) and emission spectra (715 nm) are investigated. The article also discusses the stability and selectivity of the probe and its ability to detect LAP in complex samples. Cellular imaging experiments demonstrate the NATP specificity and selectivity in detecting LAP activity and its inhibition. Animal models of liver and lung metastasis are used to evaluate the probe's imaging capabilities, showing its ability to accurately locate and detect metastatic lesions. The article concludes by emphasizing the potential applications of the NTAP probe in early tumor diagnosis, treatment monitoring, and the study of tumor metastasis mechanisms.

Sleep deprivation boosts O2·- levels in the brains of mice as visualized by a Golgi apparatus-targeted ratiometric fluorescence nanosensor.

Sleep deprivation (SD) is highly prevalent in the modern technological world. Emerging evidence shows that sleep deprivation is associated with oxidative stress. At the organelle level, the Golgi apparatus actively participates in the stress response. In this study, to determine whether SD and Golgi apparatus stress are correlated, we rationally designed and fabricated a novel Golgi apparatus-targeted ratiometric nanoprobe called Golgi dots for O2·- detection. This probe exhibits high sensitivity and selectivity in cells and brain slices of sleep-deprived mice. Golgi dots can be readily synthesized by coprecipitation of Golgi-F127, an amphiphilic polymer F127 modified with a Golgi apparatus targeting moiety, caffeic acid (CA), the responsive unit for O2·-, and red emissive carbon nanodots (CDs), which act as the reference signal. The fluorescence emission spectrum of the developed nanoprobe showed an intense peak at 674nm, accompanied by a shoulder peak at 485nm. As O2·- was gradually added, the fluorescence at 485nm continuously increased; in contrast, the emission intensity at 674nm assigned to the CDs remained constant, resulting in the ratiometric sensing of O2·-. The present ratiometric nanoprobe showed high selectivity for O2·- monitoring due to the specific recognition of O2·- by CA. Moreover, the Golgi dots exhibited good linearity with respect to the O2·- concentration within 5 to 40μM, and the limit of detection (LOD) was ~ 0.13μM. Additionally, the Golgi dots showed low cytotoxicity and an ability to target the Golgi apparatus. Inspired by these excellent properties, we then applied the Golgi dots to successfully monitor exogenous and endogenous O2·- levels within the Golgi apparatus. Importantly, with the help of Golgi dots, we determined that SD substantially elevated O2·- levels in the brain.

Refolding SDS-mediated partially-unfolded proteins: A distinguishing role of tetraalkylammonium ionic liquids via mixed micellar aggregation

The current study reports a new strategy for ionic liquid (ILs) assisted refolding of sodium dodecyl sulfate (SDS)-induced partially unfolded protein via mixed micellar aggregate formation between SDS and the ionic liquid. This approach can indeed be utilized to keep many essential and sensitive proteins as active and prolong their shelf life. For SDS-induced partially unfolded proteins, the ionic liquid has been identified to function as a refolding agent. The phenomenon has been observed by us for the first time and we have thoroughly investigated the same utilizing a variety of spectroscopic, microscopic approaches, and attempted to rationalize from computational techniques as well. The steady-state fluorescence emission spectra and time-resolved fluorescence decay show that both the intrinsic emission intensity and the average lifetime, respectively, of the surfactant-induced partially-unfolded protein increase in the presence of ionic liquid, indicating a possible reversal of unfolding (refolding) of the protein (up to ∼95 % revival of luminescence intensity and average lifetime with respect to the native protein). The CD and FTIR results also confirmed that the α-helical content of the pre-unfolded protein reverts substantially and is very close to that of the native protein. To understand the refolding process of SDS-induced partially-unfolded protein, we have further studied the structural recovery of urea-induced pre-denatured protein utilizing the same ionic liquid. Interestingly, no such refolding was observed in this case. From the experimental results, it appears that ionic liquid is involved in scavenging the unfolding surfactant monomers by forming mixed-micellar aggregates where the ion-ion attachment is likely to have impact on the said process.