Efficient Fluorescence Research Articles

Advanced X-ray absorption spectroscopy under high pressures at the ESRF beamline ID12

ABSTRACT This paper reports on advanced instrumentation for high pressure research developed for the ESRF beamline ID12 which is dedicated to polarization-dependent X-ray absorption spectroscopy at photon energies from 2 to 15 keV. Emphasis is laid on X-ray optics, the design of diamond anvil cell adapted for tender X-ray range and compatible with low temperatures and with high magnetic field as well as a highly efficient X-ray fluorescence detection system. Several examples have been selected to illustrate the performance of the beamline and show what type of advanced spectroscopic techniques can be used to study the local electronic and magnetic properties of materials under pressure.

Red Fluorescence from Organic Microdots: Leveraging Foldamer‐Linked Azobenzene for Enhanced Stability and Intensity in Bioimaging Applications

AbstractAzobenzene, while relevant, has faced constraints in biological system applications due to its suboptimal quantum yield and short‐wavelength emission. This study presents a pioneering strategy for fabricating organic microdots by coupling foldamer‐linked azobenzene, resulting in robust fluorescence intensity and stability, especially in aggregated states, thereby showing promise for bioimaging applications. Comprehensive experimental and computational examinations elucidate the mechanisms underpinning enhanced photostability and fluorescence efficacy. In vitro and in vivo evaluations disclose that the external layer of cis‐azo‐foldamer microdots performs a self‐sacrificial function during photo‐bleaching. Consequently, these red‐fluorescent microdots demonstrate extraordinary structural and photochemical stabilities over extended periods. The conjugation of a β‐peptide foldamer to the azobenzene chromophore through a glycine linker instigates a blue‐shifted and amplified π*–n transition. Molecular dynamics simulations reveal that the aggregated state of cis‐azo‐foldamers fortifies the stability of cis isomers, thereby augmenting fluorescence efficiency. This investigation furnishes crucial insights into conceptualizing novel, biologically inspired materials, promising stable and enduring imaging applications, and carries implications for diverse arenas such as medical diagnostics, drug delivery, and sensing technologies.

A multifunctional sensor for detecting tetracycline, 4-nitrophenol, and pesticides

In recent years, due to the abuse of antibiotics, nitro explosives and pesticides, which have caused great harm to the environment and human health, social concerns have prompted researchers to develop more sensitive detection platforms for these pollutants. In this paper, a novel two-dimensional Zn (II) coordination polymer, [Zn(L)0.5(1,2-bimb)]·DMF (1), [H4L=[1,1′:4′,1′’-terphenyl]-2, 2′’,4, 4′’ −tetracarboxylic acid, 1,2-bimb = 1,2-bis(imidazol-1-ylmethyl)benzene] was synthesized using a hydro-solvothermal method. Among commonly used organic solvents, 1 exhibits significant stability. Fast and efficient fluorescence response can be achieved for tetracycline (TET), 4-nitrophenol (4-NP), fluazinam (FLU), and abamectin benzoate (AMB) with low detection limits. A binary intelligent logic gate device with FLU and AMB as chemical input signals is successfully constructed, which provides a new idea for biochemical detection. In addition, a portable visual test paper has been prepared, which has high sensitivity, good selectivity, and simple operation. It can be used for rapid detection of pollutants in daily life and has broad application prospects. Finally, a detailed discussion was conducted on the fluorescence sensing mechanism of 1 for detecting TET, 4-NP, AMB and FLU.

Click generated photochromic naphthalenediimide-dithienylethene diad: Application in deciphering secret codes

Photochromic molecules with efficient fluorescence switching capability remain a core research interest among the scientific community for the application in security technologies and anti-counterfeiting measures. A dithienylethene-naphthalene diimide diad was designed and synthesized using Cu(I) catalysed click reaction between a fluorescent core substituted naphthalene diimide (cNDI) and photochromic dithienylethene (DTE) molecule, which demonstrated excellent photocyclization (ksolution = 0.0359 s−1, ksolid = 0.0122 s−1) and photocycloreversion (ksolution = 0.01737 s−1, ksolid = 0.00456 s−1) dynamics with high fluorescence quantum yield (5o ΦF = 0.39, PSS ΦF = 0.05). The fluorescence property of the molecule was switched ‘on-off’ by UV and visible light irradiation respectively via Förster resonance energy transfer (FRET) mechanism in solution state as well as in solid state, which was further corroborated with DFT studies. In view of efficient fluorescence switching behaviour and high fatigue resistance properties (25 cycles), the molecule was successfully applied in secret code encryption-decryption purposes using barcode demonstrating real-life applicability of the molecule in security technologies.

Comparing the quantum use efficiency of red and far-red sun-induced fluorescence at leaf and canopy under heat-drought stress

Sun-Induced chlorophyll Fluorescence (SIF) is the most promising remote sensing signal to monitor photosynthesis in space and time. However, under stress conditions its interpretation is often complicated by factors such as light absorption and plant morphological and physiological adaptations. To ultimately derive the quantum yield of fluorescence (ΦF) at the photosystem from canopy measurements, the so-called escape probability (fesc) needs to be accounted for.In this study, we aim to compare ΦF measured at leaf- and canopy-scale to evaluate the influence of stress responses on the two signals based on a potato mesocosm heat-drought experiment. First, we compared the performance of recently proposed reflectance-based approaches to estimate leaf and canopy red fesc using data-supported simulations of the radiative transfer model SCOPE. While the leaf red fesc showed a strong correlation (r2 ≥ 0.76), the canopy red fesc exhibited no relationship with the SCOPE retrieved red fesc in our experiment. We therefore propose modifications to the canopy model to address this limitation.We then used the modified models of red fesc, along with an existing model for far-red fesc to analyse the dynamics of leaf and canopy red and far-red fluorescence under increasing drought and heat stress conditions. By incorporating fesc, we obtained a closer agreement between leaf and canopy measurements. Specifically, for red fesc, the r2 of the two variables increased from 0.3 to 0.50, and for far-red fesc, from 0.36 to 0.48.When comparing the dynamics of the quantum yield of red and far-red fluorescence (ΦF,687 and ΦF,760) under increasing stress, we observed a statistically significant decrease of both leaf and canopy ΦF,687 as well as leaf ΦF,760, as drought and heat conditions intensified. Canopy ΦF,760, on the contrary, did not exhibit the same trend, since measurements under low stress conditions showed a wider spread and lower median than under high stress conditions. Finally, we analysed the sensitivity of ΦF,687 and ΦF,760 to changing solar incidence angle, by comparing the variability of the measurements without and with mesocosm rotation. Our results suggest that the variation in ΦF,760 strongly increased with changing solar incidence angle. These findings highlight the need for further research to understand the causes of discrepancies between leaf and canopy scale ΦF,760. On the contrary, the underutilised and understudied ΦF,687 showed great potential in assessing plant responses to drought and heat stress.

Morphological insights into uncompetitive fluorescence of coal-based carbon dots and strategies for improvement

The findings of the research indicate that coal-derived carbon dots (CDs), produced through top-down methods, exist as a blend of graphene quantum dots (GQDs), carbon quantum dots (CQDs), and carbon nanodots (CNDs). Within this mixture, numerous individual particles are dispersed, each containing multiple sp2-carbon domains, suggesting the presence of multiple fluorescent centers of varying sizes. These fluorescent centers scatter photon energy, leading to a wide full width at half maximum (FWHM >80 nm). To tackle this issue, the study significantly improves the fluorescence efficiency of coal-based CDs by employing a nitrogen-doping approach. Additionally, these nitrogen-doped CDs are combined with polyvinyl alcohol (PVA) to formulate secure inks exhibiting solid-state fluorescence and room-temperature phosphorescence (RTP) properties, showcasing their potential for anti-counterfeiting applications in safeguarding important documents and artworks.

Phosphinate Esters as Novel Warheads for Quenched Activity-Based Probes Targeting Serine Proteases.

Quenched activity-based probes (qABP) are invaluable tools to visualize aberrant protease activity. Unfortunately, most studies so far have only focused on cysteine proteases, and only a few studies describe the synthesis and use of serine protease qABPs. We recently used phosphinate ester electrophiles as a novel type of reactive group to construct ABPs for serine proteases. Here, we report on the construction of qABPs based on the phosphinate warhead, exemplified by probes for the neutrophil serine proteases. The most successful probes show sub-stoichiometric reaction with human neutrophil elastase, efficient fluorescence quenching, and rapid unquenching of fluorescence upon reaction with target proteases.

Fluorescent detection of nitrofuran antibiotics with a recordly brilliant covalent organic framework

The antibiotic residues in the water have serious effects on ecological security despite its importance for human in countering bacterium infection. The effective detection of antibiotics in drinking water could give fast, accurate diagnostic evidence, and help prevent antibiotic contamination. Herein, we report a novel fluorescent covalent organic framework (TAPA-BTD-COF) for the highly effective detection of nitrofuran antibiotics. TAPA-BTD-COF is synthesized by condensation of benzothiadiazole and tris(4-aminophenyl) amine. It exhibits an extremely strong blue fluorescence and has a record absolute fluorescence quantum yield (PLQY) in organic solvents. Besides, the COF had strong light-absorption. These properties rendered it very brilliant fluorescence, which is convenient for achieving fluorescent sensing applications. TAPA-BTD-COF exhibited efficient turn-off fluorescence response to four different kinds of nitrofuran antibiotics. Moreover, TAPA-BTD-COF fluorescence sensor exhibited a fast response to nitrofuran antibiotics with a wide detection range and linear relationship, with satisfactory LOD of 0.10 μM. And the rapid response can be achieved within 10 s. Real samples of three kinds of different water and three different kinds of meat were analyzed by adding standard recovery test. The experimental results indicated that the fluorescent sensor exhibited paralleled excellent recovery in comparison with ISO standard liquid-chromatography method. Besides, IR and XPS experiments were conducted to investigate the underlying mechanism for this efficient fluorescence sensing. The results revealed a static quenching mechanism by forming electron donor–acceptor adducts between COF sensor electron-rich triphenylamine group and nitrofuran antibiotics electron-deficient nitrofuran groups.

Fluorescence turn-on detection of arsenite in rice and seawater samples using bisphosphonate-functionalised carbon quantum dots

ABSTRACT In this paper, we illustrate an efficient and simple fluorescence (FL) sensing approach for the specific determination of arsenite (As(III)) in aqueous solution by alendronate-functionalised carbon quantum dots (A-CQDs) as a turn-on fluorescent probe. A-CQDs exhibit linear FL turn-on response towards the increasing concentration of As(III) analyte with a limit of detection of 0.007 µM and a linear range of 0.03–1.87 µM. The selectivity study demonstrates that the A-CQDs are very selective for As(III) detection, even at a higher concentration of other interfering ions. The sensing pathway for the sensitivity of A-CQDs assay to quantify As(III) ions is expected to rely on the chelation-enhanced FL (CHEF) mechanism between A-CQDs and the analyte. This mechanism is verified by the density functional theory methodology. The practical application of this simple and reliable sensor is demonstrated by assaying As(III) in rice and seawater samples, which confirms that A-CQDs have good potential for real sample analysis in food and environmental samples.

Active Hydrogen Free, Z-Isomer Selective Isatin Derived "Turn on" Fluorescent Dual Anions Sensor.

An efficient and anions fluorescence "on-off" sensor of 1-(prop-2-yn-1-yl)-3-(quinolin-3-ylimino)indolin-2-one (PQI) has been developed for the selective sensing of dual anions of F- and NO3- ions in aqueous medium. Active hydrogen and Lewis acidic binding sites free, Z- isomer of isatin based π-conjugated quinoline exhibited excellent sensing activity against F- and NO3- ions in UV light. The fluorescence turns on the process accomplished via the PET "on-off" mechanism. The interaction between probe molecule and anions is thought to be a non-covalent interaction of the low electron density covalently bonded N-methylene moiety of propargyl isatin (-N-CH2-) of probe molecule with F- ion and the terminal acidic proton of propargyl group of isatin (-C≡C-H) with NO3- ions. The modes of anions binding with PQI and plausible mechanisms are proposed by 1H and 13C NMR titrations. The selectivity of anions sensing may be offered by the bucked structure of the Z-isomer. The calculated association constant values for PQI and F- and NO3- are ions 2.5 × 104M-1 and 2.2 × 103M-1, respectively, indicating strong binding interaction between the PQI and anions. The association nature of anions and probes was analyzed by a Jobs plot and the finding indicates both F- and NO3- ions are in 1:1 complexation with PQI. The limit of detection (LOD) of the probe with F- and NO3- ions is calculated and is to be 6.91 × 10-7M and 9.93 × 10-7M, respectively. The proposed PQI fluorophore possesses a low limit of detection (LOD) for both F- and NO3- ions which is within the WHO prescribed detection limit.

L-Arginine Doped Carbon Nanodots from Cinnamon Bark for Improved Fluorescent Yeast Cell Imaging.

In this study, we present an economical and efficient synthesis method for carbon nanodots (CNDs) derived from cinnamon bark wood powder, with the incorporation of L-arginine as a dopant at varying ratios (Cinnamon : L-Arginine - 1:0.25, 1:0.5) via a hydrothermal reaction. Extensive structural and optical characterization was conducted through techniques such as FTIR, XRD, HR-TEM, DLS, UV-Vis, and PL spectra, providing a comprehensive understanding of the properties of CNDs and doped-CNDs. Quantum yields (QY) were quantified for synthesized materials, contributing to the assessment of their fluorescence efficiency. The synthesized CNDs were successfully applied for bioimaging of yeast cells, employing fluorescence microscopy to visualize their interaction. Remarkably, L-arginine-doped CNDs exhibited enhanced fluorescence, showcasing the influence of the dopant. The nature of these CNDs was rigorously investigated, confirming their biocompatibility. Notably, this work presents a novel approach to synthesizing CNDs from a renewable and sustainable source, cinnamon bark wood powder, while exploring the effects of L-arginine doping on their optical and biological properties. This work not only contributes to the synthesis and characterization of CNDs but also highlights their potential for diverse applications, emphasizing their structural, optical, and biological attributes. The findings underscore the versatility of CNDs derived from cinnamon bark wood powder and their potential for advancing biotechnological and imaging applications.

Solvent effects on the ESIPT emission of salicylaldehyde Schiff base derivative: A theoretical reconsideration

Salicylaldehyde Schiff base derivatives have potential applications in bioimaging, chemical sensors and organic luminescence materials because of their high fluorescence quantum yield with the excited-state intramolecular proton transfer (ESIPT) process. Recently, Shu et al. studied the luminescent mechanism of the Et2N-substituted salicylaldehyde Schiff base compound (DDHAC) in solvents [Dyes and Pigments 195 (2021) 109708]. It showed double-peaked bands in an n-hexane solvent but a single-peaked band in an acetonitrile solvent. They suggested that the open-enol in the acetonitrile solvent was the dominant species. They considered that open-enol fluorescence and ESIPT fluorescence constituted a dual fluorescent phenomenon in the n-hexane solvent. However, because acetonitrile is a non-protonic solvent, DDHAC molecules in acetonitrile mainly existed as the lower-energy hydrogen-bonded enol form rather than the open-enol form alone. In addition, the open-enol did not undergo the ESIPT process in n-hexane. Therefore, the luminescence mechanism of the DDHAC molecules in n-hexane and acetonitrile solvents needs to be reconsidered. In this study, we investigated the DDHAC molecules in n-hexane and acetonitrile solvents using the density functional theory and time-dependent density functional theory. The potential energy surfaces and optimisation of structures elucidated that the DDHAC molecules in n-hexane and acetonitrile solvents underwent the ESIPT process. The calculated fluorescence peaks demonstrated that the single-peaked broad emission band in the acetonitrile solvent was formed by the combination of the hydrogen-bonded enol* and keto* forms rather than open-enol*. Moreover, the dual fluorescence peaks in the n-hexane solvent were reattributed to the open-enol* form and hydrogen-bonded enol* form. The lack of keto* fluorescence in the n-hexane solvent was attributed to diminished charge coupling in comparison to the enol* form. Our results revise the mechanism of the DDHAC molecules in n-hexane and acetonitrile solvents, providing guidance for designing efficient organic fluorescence probes.

Efficient and ultra-high luminance orange-red organic light emitting diode (OLED) based on triphenylamine-benzothiadiazole-phenoxazine hybrid molecule with hybrid local and charge-transfer (HLCT) characteristic

Due to the energy gap law, red emission needs relatively narrow energy gap, thus the nonradiative transition rate (knr) grows exponentially and eventually impacts the materials fluorescent efficiency. Here, an orange-red emission donor-acceptor-π-donor (D-A-π-D’) material N, N-diphenyl-4-(7-(4-(10-phenyl-10 H-phenoxazin-3-yl) phenyl) benzo [c] (Huang et al., 2019; Park et al., 2008; Caspar et al., 1982) [1,2,5] thiadiazol-4-yl) aniline (TBphPP) was designed and synthesized. Introducing a benzene π-bridge between the strong donor 10-phenyl-10H-phenoxazin (PPOX) and acceptor 2,1,3-benzothiadiazole (BTZ) not only is able to stretch the molecular conjugation so as to increase the proportion of LE state in hybrid local and charge-transfer (HLCT) state but also increase the overlap area of the electron cloud to improve luminous efficiency. As a result, the non-doped organic light-emitting diode (OLED) of TBphPP exhibited high luminance of 17,886 cd m−2 and relatively high exciton utilization efficiency (EUE) of 44 % with a standard red electroluminescent peak at 620 nm. Importantly, the optimized doped device based on TBphPP achieved high performance that the maximum external quantum efficiency (EQEmax) was up to 9.86 % with a higher EUE of 66.2 % and the efficiency roll-off (ηroll-off) at 100,000 cd m−2 was only 3.55 %. Simultaneously, it has reached ultra-high luminescence of 180,583 cd m−2, high current efficiency of 29.02 cd A−1 and power efficiency of 16.47 l m W−1. To our knowledge, the TBphPP device with such ultra-high luminance and high efficiency is one of the best performance orange-red materials based on HLCT characteristic.

A highly efficient, selective, reversible and ultra-sensitive fluorescence “Turn-ON” chemosensor for aluminium ions by a novel Schiff base

The synthesis of a Schiff base-based chemosensor, denoted as H6L, was accomplished through the condensation reaction of Isophthalohydrazide and 2,6-dihydroxybenzaldehyde in an ethanol solvent. The resulting compound was further characterized using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, as well as high-resolution mass spectrometry (HRMS). Extensive research has been conducted on several facets of metal sensing phenomena, revealing that the Schiff base H6L demonstrates discerning and expeditious fluorescence sensing characteristics specifically towards Al (III) in acetonitrile. The purported method detects Al (III) can be ascribed to the suppression of photo-induced electron transfer (PET) and the enhanced chelation-induced fluorescence (CHEF). The stoichiometry of metal–ligand complexes (2:1) was determined using Job’s plots titrations, HRMS and subsequently confirmed using NMR titration studies. The H6L sensors demonstrated remarkable fluorescence sensing capabilities in acetonitrile, with a low detection limit (LOD) of 0.44 μM. This LOD is suitably low for the detection of Al3+, which is commonly found in many environmental and biological systems. Fluorescence lifetime measurement provides additional evidence of complexation of H6L with Al (III). The reversibility of the sensor was demonstrated through the introduction of pyrophosphate (PPi), which forms a complex with aluminium ions, thereby releasing the chemo sensor for subsequent utilization. The findings suggest that H6L has the potential to serve as a viable probe for the detection and identification of Al3+ ions.

High‐Efficiency Luminescent Solar Concentrators Based on Carbon Dots with Simultaneously Ultrabright Solid‐State and Liquid‐State Luminescence

AbstractCarbon dots (CDs) are ideal fluorophores for optoelectronic devices. However, it is still a great challenge to obtain CDs with high solid‐state photoluminescence quantum yields (PLQYs). In this work, it is first reported that the barium‐doped CDs (Ba‐CDs), which can be simply synthesized on a large scale via a direct one‐step heating approach using an open vessel. The as‐synthesized Ba‐CDs exhibit ultrabright luminescence both in liquid and solid states. The as‐synthesized Ba‐CDs with a scale of 8.6 g per batch show a Stokes shift of ≈0.68 eV and high PLQYs of 80.8% and 66.8% in liquid and solid state, respectively. Interestingly, an efficient fluorescence enhancement phenomenon occurs when Ba‐CDs are mixed with polyvinylpyrrolidone (PVP), which reveals the critical issue of compatibility between CDs and polymer matrix can be well resolved. As a proof‐of‐concept, the Ba‐CDs are employed as fluorophores for high‐efficiency luminescent solar concentrator (LSC) fabrication. The Ba‐CDs@PVP‐based LSC has a PLQY of 88.78%, showing a breakthrough optical conversion efficiency of 7.16% and power conversion efficiency of 6.87% under natural light irradiation (40 mW cm−2). The results demonstrate the potential application of the ultrabright Ba‐CDs in efficient photovoltaic devices.

Biocompatible polymer-coated magneto-fluorescent super nanoparticles for the homing of mesenchymal stem cells

Stem cell plays an important role in the clinical field. However, the effective delivery of stem cells to the targeted site relies on the efficient homing of the cells to the site of injury. In view of that, fluorescent magnetic nanoparticles stick out due to their wide range of enabling functions including cellular homing and tracking. The present study unravels the synthesis of polymer-coated biocompatible and fluorescent magnetic nanoparticles (FMNPs) by a single-step hydrothermal synthesis method. Importantly, the facile method developed the biological super nanoparticles consisting of the magnetic core, which is surrounded by the fluorescent nanodot-decorated polymeric shell. The synthesized particles showed an amorphous nature, and superparamagnetic properties, with efficient fluorescence properties of emission at the blue range (̴ 410 nm). The FMNP labeling showed the mesenchymal stem cell (MSC) homing to the desired site in the presence of an external magnetic field. The in-house synthesized nanoparticles showed significant cytocompatibility and hemocompatibility in vitro as well as in vivo conditions owing to their surface coating. This unprecedented work advances the efficient internalization of FMNPs in MSCs and their enhanced migration potential provides a breakthrough in stem cell delivery for therapeutic applications. Statement of significanceThe bi-modal fluorescent magnetic nanoparticles hold a promising role in the biomedical field for mesenchymal stem cell homing and tracking. Hence, in this study, for the first time, we have synthesized the fluorescent magnetic nanoparticle with polymer coating via an easy single-step method. The nanoparticle with a polymer coat enhanced the biocompatibility and effortless internalization of the nanoparticle into mesenchymal stem cells without hampering the native stem cell properties. Furthermore, the enhanced migration potential of such magnetized stem cells and their homing at the target site by applying an external magnetic field opened up avenues for the smart delivery of mesenchymal stem cells at complex sites such as retina for the tissue regeneration.

The efficiency of chlorophyll fluorescence as a selection criterion for salinity and climate aridity tolerance in barley genotypes.

In the Near East and North Africa (NENA) region, crop production is being affected by various abiotic factors, including freshwater scarcity, climate, and soil salinity. As a result, farmers in this region are in search of salt-tolerant crops that can thrive in these harsh environments, using poor-quality groundwater. The main staple food crop for most of the countries in this region, Tunisia included, is barley. The present study was designed to investigate the sensitivity and tolerance of six distinct barley genotypes to aridity and salinity stresses in five different natural field environments by measuring their photosynthetic activity. The results revealed that tolerant genotypes were significantly less affected by these stress factors than sensitive genotypes. The genotypes that were more susceptible to salinity and aridity stress exhibited a significant decline in their photosynthetic activity. Additionally, the fluorescence yields in growth phases J, I, and P declined significantly in the order of humid environment (BEJ), semi-arid site (KAI), and arid environment (MED) and became more significant when salt stress was added through the use of saline water for irrigation. The stress adversely affected the quantum yield of primary photochemistry (φP0), the quantum yield of electron transport (φE0), and the efficiency by trapped excitation (ψ0) in the vulnerable barley genotypes. Moreover, the performance index (PI) of the photosystem II (PSII) was found to be the most distinguishing parameter among the genotypes tested. The PI of sensitive genotypes was adversely affected by aridity and salinity. The PI of ICARDA20 and Konouz decreased by approximately 18% and 33%, respectively, when irrigated with non-saline water. The reduction was even greater, reaching 39%, for both genotypes when irrigated with saline water. However, tolerant genotypes Souihli and Batini 100/1B were less impacted by these stress factors.The fluorescence study provided insights into the photosynthetic apparatus of barley genotypes under stress. It enabled reliable salinity tolerance screening. Furthermore, the study confirmed that the chlorophyll a fluorescence induction curve had an inflection point (step K) even before the onset of visible signs of stress, indicating physiological disturbances, making chlorophyll fluorescence an effective tool for identifying salinity tolerance in barley.

Lysozyme functionalized silver nanoclusters as a dual channel optical sensor for the effective determination of glutathione

This article describes the development of a facile and efficient fluorescence sensor for the determination of glutathione (GSH). Presence of the antioxidant glutathione in blood serum is considered as a biomarker for catastrophe like colorectal cancer. Silver nanoclusters with strong fluorescence and good water solubility synthesized from relatively cheaper precursors are one of the species very much explored in fluorescence sensors and bioimaging. Here, Chicken egg derived-lysozyme functionalized silver nanoclusters (Lyz AgNCs) with red fluorescence emission has been synthesized and developed to a turn-off fluorescence sensor for GSH through which colorimetric determination is also possible. Due to the ground state ‘Ag–S’ interaction between Lyz AgNCs and GSH, the determination of the analyte is possible from 1.00 × 10−5 M to 1.00 × 10−6 M via fluorimetric and from 9.00 × 10−6 to 8.00 × 10−7 M via spectrophotometric techniques with a limit of detection 2.86 × 10−7 M and 4.76 × 10−7 M, respectively. Selectivity of the sensor has been studied and applicability of the sensor in artificial blood serum samples has been demonstrated.

Enhanced luminescence using the core‐shell‐shell structure of 3‐mercaptopropionic acid‐capped ZnSe/ZnS: Mn/ZnS quantum dot

AbstractIn this study, we used the surface stabilizer 3‐mercaptopropionic acid (MPA) to synthesize ZnSe quantum dots in nontoxic aqueous solvents. Because of the –COOH group, MPA is an SH‐R‐COOH molecule that is added to improve the dispersion and quantum dot (QD) compatibility with antibodies. The different structures ZnSe, Mn‐doped ZnSe, Mn‐doped ZnSe/ZnS, and ZnSe/Mn‐doped ZnS/ZnS were investigated to find the optimum photoluminescence (PL). The structure and distribution element of ZnSe/Mn‐doped ZnS/ZnS QD were analyzed by the high‐resolution TEM image and scanning transmission electron microscopy. This finding of the ZnS buffer layer helps to reduce the defect lattice of QDs, which increases PL significantly. The highest PL intensity of ZnSe/ZnS:Mn/ZnS is significantly more than that of ZnSe and ZnSe/ZnS 6.2 and 3.3 times, respectively. In addition, the fluorescence efficiency of ZnSe/ZnS:5%Mn/ZnS‐MPA was 74.37% higher than that of ZnSe:5%Mn/ZnS‐MPA (55.04%) in ZnS buffer.

Regulatory mechanisms of plant rhizobacteria on plants to the adaptation of adverse agroclimatic variables

The mutualistic plant rhizobacteria which improve plant development and productivity are known as plant growth-promoting rhizobacteria (PGPR). It is more significant due to their ability to help the plants in different ways. The main physiological responses, such as malondialdehyde, membrane stability index, relative leaf water content, photosynthetic leaf gas exchange, chlorophyll fluorescence efficiency of photosystem-II, and photosynthetic pigments are observed in plants during unfavorable environmental conditions. Plant rhizobacteria are one of the more crucial chemical messengers that mediate plant development in response to stressed conditions. The interaction of plant rhizobacteria with essential plant nutrition can enhance the agricultural sustainability of various plant genotypes or cultivars. Rhizobacterial inoculated plants induce biochemical variations resulting in increased stress resistance efficiency, defined as induced systemic resistance. Omic strategies revealed plant rhizobacteria inoculation caused the upregulation of stress-responsive genes—numerous recent approaches have been developed to protect plants from unfavorable environmental threats. The plant microbes and compounds they secrete constitute valuable biostimulants and play significant roles in regulating plant stress mechanisms. The present review summarized the recent developments in the functional characteristics and action mechanisms of plant rhizobacteria in sustaining the development and production of plants under unfavorable environmental conditions, with special attention on plant rhizobacteria-mediated physiological and molecular responses associated with stress-induced responses.