Efficient Fluorescent Sensor Research Articles

Fabrication of lanthanum-mediated carbon quantum dots for the fluorescent detection of aniline and enhancement in photocatalytic degradation efficiency of zirconium oxide nanoparticles

A unique and efficient fluorescent sensor was developed by doping carbon quantum dots (CQDs) with La(III) ions by microwave treatment. The La-CQDs exhibit an average particle size of 4.8 nm, a quantum yield of 16 % and blue fluorescence emission when excited at 360 nm. Furthermore, the La-CQDs were successfully incorporated into zirconium oxide nanoparticles (La-CQD-ZrO2) and designed as a superior photocatalyst for the degradation of refractory pollutants. Both the sensor and photocatalyst were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman analysis, ultraviolet–visible (UV–Vis) spectroscopy, Photoluminescence (PL) spectroscopy, zeta potential analysis, dynamic light scattering (DLS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry analysis. As a PL-based sensor, the La-CQDs displayed outstanding selectivity towards toxic chemical aniline with a limit of detection (LOD) of 10 nM within the linear range 0–2 μM. The excellent results obtained in real sample analysis promise the use of La-CQDs as an aniline sensor in industrial-level applications. The photocatalytic performance of La-CQD-ZrO2 was superior to that of pure ZrO2 and CQD-ZrO2 with more than 90 % degradation efficiency towards rhodamine B (Rh B), sunset yellow (SY), methyl orange (MO), 2,4-dichloro phenoxy acetic acid (2,4-D), and cefalexin. The synthesized composite showed excellent promise as a quick and affordable solution for removing industrial dye from wastewater.

A Simple Live Cell Imaging "Turn-On" Fluorescence Probe for the Selective and Sensitive Detection of Aqueous Hg2+ Ions.

A simple, efficient, and reversible fluorescent sensor probe, PBA (2,6-dimethyl pyrone barbituric acid conjugate), comprised of a pro-aromatic donor conjugated with a barbituric acid, was developed for the detection of highly toxic mercuric ions. The probe showed high selectivity and "Turn-On" fluorescence response towards Hg2+ among various metal cations such as Na+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, and Pb2+, in both homogeneous and microheterogeneous micelle medium sodium dodecyl sulphate (SDS). The binding stoichiometry, limit of detection (LOD), and binding constant for the PBA-Hg complex were determined. The mechanism of binding was ascertained using the N,N'-dimethylbarbituric acid conjugate of 2,6-dimethylpyran (PDMBA), where no binding interaction by deprotonation is possible. In the presence of cysteamine hydrochloride and trifluoroacetic acid (TFA), the complexation of Hg2+ with PBA was demonstrated to be reversible, indicating its potential for the development of reusable sensors. Moreover, the practical applicability of PBA in monitoring Hg2+ in living cells was also evaluated.

Design and Synthesis of an Efficient Fluorescent Probe Based on Oxacalix[4]arene for the Selective Detection of Trinitrophenol (TNP) Explosives in Aqueous System.

We present the synthesis of a new oxacalix[4]arene system, DMANSOC, wherein two 5-(dimethylamino)-1-naphthalene sulfonamide subunits are attached to the lower rims of the basic oxacalix[4]arene platform. Extensive spectrophotometric studies were conducted to investigate the selectivity and sensitivity of DMANSOC towards nitroaromatic explosives. Detailed analysis of spectrophotometric data, utilizing techniques such as Stern-Volmer, Benesi-Hildebrand, Job's plot, and interference study, unequivocally demonstrated the effectiveness of DMANSOC as a highly efficient fluorescent sensor for 2,4,6-trinitrophenol explosive (TNP) detection in an aqueous medium. The sensor exhibited a linear concentration range of 7.5 μM to 50 μM, with a low detection limit of 4.64 μM and a high binding affinity of 2.45 × 104M towards TNP. Furthermore, the efficiency of the sensor in environmental samples contaminated with TNP was evaluated, yielding excellent recovery rates. Complementary DFT calculations and molecular dynamics simulations were performed to elucidate the mechanism behind the selective fluorescence quenching of DMANSOC in the presence of TNP.

Visible Light and Microwave-Mediated Rapid Trapping and Release of Singlet Oxygen Using a Coordination Polymer.

Due to its high reactivity and oxidative strength, singlet oxygen (1 O2 ) is used in a variety of fields including organic synthesis, biomedicine, photodynamic therapy and materials science. Despite its importance, the controlled trapping and release of 1 O2 is extremely challenging. Herein, we describe a one-dimensional coordination polymer, CP1, which upon irradiation with visible light, transforms 3 O2 (triplet oxygen) to 1 O2 . CP1 consists of CdII centers bridged by 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene ligands which undergo a [4+2] cycloaddition reaction with 1 O2 , resulting in the generation of CP1-1 O2 . Using microwave irradiation, CP1-1 O2 displays efficient release of 1 O2 , over a period of 30 s. In addition, CP1 exhibits enhanced fluorescence and has an oxygen detection limit of 97.4 ppm. Theoretical calculations reveal that the fluorescence behaviour is dominated by unique through-space conjugation. In addition to describing a highly efficient approach for the trapping and controlled release of 1 O2 , using coordination polymers, this work also provides encouragement for the development of efficient fluorescent oxygen sensors.

Visible Light and Microwave‐Mediated Rapid Trapping and Release of Singlet Oxygen Using a Coordination Polymer

AbstractDue to its high reactivity and oxidative strength, singlet oxygen (1O2) is used in a variety of fields including organic synthesis, biomedicine, photodynamic therapy and materials science. Despite its importance, the controlled trapping and release of 1O2 is extremely challenging. Herein, we describe a one‐dimensional coordination polymer, CP1, which upon irradiation with visible light, transforms 3O2 (triplet oxygen) to 1O2. CP1 consists of CdII centers bridged by 9,10‐bis((E)‐2‐(pyridin‐4‐yl)vinyl)anthracene ligands which undergo a [4+2] cycloaddition reaction with 1O2, resulting in the generation of CP1−1O2. Using microwave irradiation, CP1−1O2 displays efficient release of 1O2, over a period of 30 s. In addition, CP1 exhibits enhanced fluorescence and has an oxygen detection limit of 97.4 ppm. Theoretical calculations reveal that the fluorescence behaviour is dominated by unique through‐space conjugation. In addition to describing a highly efficient approach for the trapping and controlled release of 1O2, using coordination polymers, this work also provides encouragement for the development of efficient fluorescent oxygen sensors.

Study of the pH effect on the optical and morphological properties of S, N self-doped carbon dots applied as fluorescent anti-counterfeiting ink and pH sensor

The pH value is an important parameter as it is part of several processes, whether environmental or biological. In this report, S, N self-doped carbon dots (CDs) were synthesized by a simple hydrothermal method using cysteine (cys) and citric acid as precursors for a detailed investigation of size, morphological, photoluminescent, and structural changes at different pH values and its use as pH sensor and fluorescent ink. The fluorescence intensity of cys-CDs was dependent on the pH, presenting a linear relationship with pH values in the range of 2.0–9.0. Using spectroscopic techniques, a mechanism for the pH-dependent fluorescence is proposed, based on the aggregation of cys-CDs and also protonation/deprotonation of surface functional groups that change the excited state. The cys-CDs were found to be efficient as fluorescent pH sensors using real samples (distilled water and tap water). Furthermore, the pH changes in cys-CDs can be used for the visual enhancement of anti-counterfeiting technologies. Thus, the results of this study show that cys-CDs can act as an efficient and pH sensitive fluorescent sensor, which can be used to measure the pH value of water samples, due to its high fluorescence intensity, and can be applied successfully as a fluorescent ink.

Modification of Carbon Dots for Metal‐Ions Detection

AbstractIt is very appealing to develop cheap, highly sensitive and efficient metal ion fluorescence sensors as traditional instrument methods are inherently costly and time‐consuming. Carbon dots (CDs) are widely used for sensing metal ions, attributing to their merits of good biocompatibility, low toxicity, easy surface modification and excellent photostability. This article reviewed the research progress of CDs as metal ion sensors in recent years, and studied their modification methods and detection performances. Finally, the challenges and opportunities of CDs as metal ion sensors were also analyzed. This article is expected to provide inspiration and help for researchers focusing on CDs as metal ion sensors.

Novel SnO2@Cu3(BTC)2 Composites as a Highly Efficient Photocatalyst and Fluorescent Sensor.

A novel SnO2@Cu3(BTC)2 composite was synthesized using a quick and affordable bottom-up approach viaimpregnation of SnO2 nanoparticles into the porous Cu3(BTC)2 metal-organic framework (MOF). This composite material is characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD) spectra, scanning electron microscope (SEM) analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis. SnO2@Cu3(BTC)2 degraded the methylene blue (MB) dye within 80min under sunlight with a maximum degradation efficiency of 85.12%. This composite easily recyclable up to five cycles with the retention of its MB degradation efficiency. Moreover, SnO2@Cu3(BTC)2 can be also used efficiently for fast sensing of 2,4,6-trinitrophenol (TNP) in water with noticeable turn-off quenching response. Its limits of detection (LOD) for TNP was 2.82µM with enhancedselectivitytoward TNP (over other NACs) as verified by competitive nitro explosive tests.Density functional theory(DFT) calculations and spectral overlap were used to assess the sensing mechanism. This composite fluorescent sensing system for TNP are demonstrated to have high selectivity and sensitivity. Our findings imply that the prepared low cost SnO2@Cu3(BTC)2 composite can be used as a superior fluorescence sensor and photo catalyst for large scale industrial applications.

Terpyridine-4-amino-1,8-naphthalimide chemosensor for discriminative fluorescent sensing of divalent metal cations at ppb level of sensitivity

A new terpyridine-4-amino-1,8-naphthalimide fluorescence sensor, TERPY-Nap, has been designed and synthesized in the analytically pure form via a one-step imidation reaction between 4-amino-1,8-naphthalic anhydride and N-[2,2′;6′,2″]Terpyridin-4′-yl-propane-1,3-diamine. The internal-charge-transfer (ICT) transition makes TERPY-Nap to be highly emissive and exhibits solvent polarity-dependent emission characteristics in different organic solvents. Inspired by the strong fluorescence, TERPY-Nap was used as an efficient fluorescence sensor for discriminative fluorescence sensing of divalent metal cations such as Cu(II), Co(II), and Ni(II) in ethanol. The initial fluorescence emission intensity of TERPY-Nap was quenched drastically upon the addition of Cu(II), Ni(II), and Co(II) ions as their nitrate salt, and the fluorescence quenching constants (KSV) were calculated to be in the order of 104–105 M−1. Furthermore, it was observed that TERPY-Nap can sense Cu(II), Ni(II), and Co(II) as low as ppb level of sensitivity and the quenched fluorescence emission of complexes can be reversed by the addition of well-known metal scavenger EDTA in ethanol. Interestingly, similar fluorescence titration studies using other metal ions like Zn(II), Cd(II), Mn(II), Ba(II), Al(III), Mg(II), and Ce(III) showed almost negligible changes in emission intensity due to their weak binding at the terpyridine receptor sites. Therefore, TERPY-Nap can be used as a potential ‘turn-off’ fluorescence chemosensor for reversible detection and trace analysis of biologically relevant and environmentally pertaining divalent metal cations.

Fluorescent sensors and rapid detection films for Fe3+ and Cu2+ based on naphthalene and cholesterol derivative organogels

Two novel gelators G1 and G2 based on naphthalene and cholesterol derivatives were designed and synthesized, which could form stable organogel in different kind of solvents. Interestingly, G2 could act as an efficient fluorescent sensor for detection of Fe3+ and Cu2+, also the self-assembly mechanism and ion response mechanism were further studied. The detection limits of G2 for Fe3+ and Cu2+ are 8.2539 × 10−6 M and 9.1426 × 10−6 M, respectively. Besides, a rapid fluorescence detection film for Fe3+ and Cu2+ were also developed.

A highly stable and efficient benzothiadiazole-based fluorescence sensor for salicylaldehyde in aqueous solution

A water-stable and pH-stable CP-based fluorescence probe (JXUST-27) can sense SA via fluorescence quenching with high selectivity and sensitivity. Remarkably, the fluorescence film and LED lamp have been further developed to detect SA.

A Highly Efficient Fluorescent Sensor Based on AIEgen for Detection of Nitrophenolic Explosives

The detection of nitrophenolic explosives is important in counterterrorism and environmental protection, but it is still a challenge to identify the nitroaromatic compounds among those with a similar structure. Herein, a simple tetraphenylethene (TPE) derivative with aggregation-induced emission (AIE) characteristics was synthesized and used as a fluorescent sensor for the detection of nitrophenolic explosives (2, 4, 6-trinitrophenol, TNP and 2, 4-dinitrophenol, DNP) in water solution and in a solid state with a high selectivity. Meanwhile, it was found that only hydroxyl containing nitrophenolic explosives caused obvious fluorescence quenching. The sensing mechanism was investigated by using fluorescence titration and 1H NMR spectra. This simple AIE-active probe can potentially be applied to the construction of portable detection devices for explosives.

Binding interactions and sensing applications of chromone derived Schiff base chemosensors via absorption and emission studies: A comprehensive review

• The review contains different experimental procedures and sensing mechanisms followed in fluorescence sensing. • This review paper compiles the synthesis of different formylchromones. • Chromones Schiff bases are efficient colorimetric and fluorescent sensors. • Chromone-based Schiff base sensors has found practical applicability’s in environmental and biological samples. Chemosensors are the molecular probes which are frequently used for analyte (metal ions, anions, explosives etc.) detection via photophysical changes. Analyte detection constitutes an active topic of research because the imbalanced consumption of these chemical species produces harmful effects to the ecosystem as well as to living beings. In recent years, several molecular probes of different frameworks are known for analyte detection. Among these, Schiff bases are more proficient and effective as compared to other chemosensors. Chromones itself possessing various physiological and photochemical properties but introduction of azomethine bond in chromones makes it useful probe for sensing applications. Colorimetric and fluorimetric sensing are promising techniques used to detect different chemical species in solvent system. They provide high sensitivity, reliability and quick response in comparison to the other reported techniques. The motive of this review is to provide better insight of the sensing mechanism of chromone derived Schiff bases and their practical utility in analyte detection to the researchers.

Constructing hollow ZIF-8/CDs@MIPs fluorescent sensor from Osmanthus leaves to specifically recognize bovine hemoglobin

To develop non-toxic, highly efficient and selective fluorescence sensors was a significance research. In this work, a novel hollow fluorescence sensor was designed with biomass carbon dots (CDs), ZIF-8 and molecularly imprinted polymers (MIPs) via aqueous polymerization. The results demonstrated such unique structure fluorescence sensor exhibited fast response time, excellent stability and highly selectively towards bovine hemoglobin (BHb). Even in a complex environment, the hollow fluorescence sensor (H-ZIF-8/CDs@MIPs) still has a good recognition effect on BHb. Under an optimized condition, the hollow fluorescence sensor was quenched linearly with BHb concentration in the range of 0.058–4.5 μM with the detection limit of 15.6 nM. In addition, a possible quenching mechanism of hollow fluorescence towards BHb was confirmed resonance energy transfer (FRET). In the actual application process, the hollow fluorescence sensor showed a better detection performance towards BHb with the recoveries ranged of 98.6–101.1 %. This work provided a strategy to design green and unique hollow fluorescence sensor for practical application.

B, N co-doped carbon dots based fluorescent test paper and hydrogel for visual and efficient dual ion detection

It is highly significant to develop water-soluble carbon dots (CDs) for ion detection in the environment via a facile and economical process. Herein, the organic molecules derived boron, nitrogen co-doped CDs (BN-CDs) with water-solubility are solvothermally synthesized towards dual ion detection. The BN-CDs emit bright tangerine fluorescence, and demonstrate a fluorescent quantum yield of 17 %. Besides, the obtained BN-CDs show a good linear relationship with Cu2+/Co2+ in a wide dynamic range of 1–8 μM, along with detection limits of 16 nM (Cu2+) and 24 nM (Co2+). The joint effect of dynamic and static quenching mechanisms is proposed as well for fluorescence quenching by Cu2+/Co2+. Furthermore, two instrument-free BN-CDs-based solid sensors (i.e., test strips and hydrogel beads) are fabricated to sensitively monitor both Cu2+ and Co2+. The paper-based sensors exhibit selective and sensitive response towards Cu2+ and Co2+ in a low-cost manner. The fluorescence hydrogel integrates comprehensive advantages of hydrogel and BN-CDs, which makes it not only conduct as efficient fluorescent sensors to detect Cu2+ and Co2+ but act as the absorbent towards removal of the ions. The simple yet reliable sensing technique developed here favor efficiently detecting and recognizing dual ions in environmental and/or biological samples.

Theoretical study on a series of naphthalimide-contained two-photon fluorescent hypochlorite probe targeting endoplasmic reticulum: response mechanism and receptor effect.

The development of detecting hypochlorous acid (HClO) in living endoplasmic reticulum has attracted much attention in the fields of biology, medicine, and pharmacy. In the present work, the one-photon absorption (OPA), one-photon emission (OPE), and two-photon absorption (TPA) properties of a series newly synthesized chemosensors with naphthalimide as the fluorophore were systematically investigated using time-dependent density functional theory in combination with response theory. Special emphasis is placed on evolution of the probes' optical properties in the presence of HClO. These compounds show drastic changes in their photoabsorption and photoemission properties when they react with HClO, indicating them to be excellent candidates as fluorescent chemosensors. To further understand the mechanisms of the two probes, we have employed the hole and electron analysis to investigate the charge transfer process for the photoemission of the molecules. The receptor effect is found to play a dominant role in the sensing performance of these probes. Specifically, two-photon absorption properties of the molecules are calculated. We have found that all probes show significant two-photon responses in the near-infrared light region. And the maximum two-photon absorption cross section of probe 2 is greatly enhanced with the presence of HClO, indicating that probe 2 can act as a potential two-photon excited fluorescent HClO probe. The theoretical investigations would be helpful to build the structure-property relationships for the naphthalimide-contained probes, providing information on the design of efficient two-photon fluorescent sensors that can be used for biological imaging of HClO in endoplasmic reticulum.

A Highly Sensitive Fibrous Luminescent Probe Based on Anthracene Triarylamine for Nitroaromatic Explosives

AbstractThe rapid, sensitive, and efficient detection of nitroaromatic explosives (NAEs) is extremely important for human health and public safety; however, it is still a big challenge, especially for the detection of trace amounts of explosive vapors. In this study, a small‐molecule luminescent probe of an anthracene triarylamine derivative was synthesized and employed as a highly efficient and sensitive sensor for the detection of NAEs, including 2,4‐dinitrotoluene (DNT), 4‐nitrotoluene (4‐NT), and nitrobenzene (NB). The fluorescence intensity varied linearly along with the concentration of NAEs in the diluted tetrahydrofuran solution. The KSV values (Stern‐Volmer equation coefficient) were 2457, 1735, and 1286 M−1 for DNT, 4‐NT, and NB, respectively (DNT>4‐NT>NB). Furthermore, polystyrene/LiCl/AnPh electrospun fibrous films were manufactured and proved to be efficient fluorescence sensors for NAEs vapor. This quenching can be ascribed to the photo‐induced electron transfer (PET) process between the AnPh probe and NAEs analytes. The large contact area between the nanofibers and analytes in the film also contributed to the efficient quenching effect. This work will stimulate the design of new fluorescent probes for electrospun fibrous NAEs sensors and pave the way for their applications in future practical fields of public safety control.

Random forest algorithm-enhanced dual-emission molecularly imprinted fluorescence sensing method for rapid detection of pretilachlor in fish and water samples

A sensitive and efficient fluorescence sensor based on dual-emission molecularly imprinted polymers (Dual-em-MIPs) was successfully developed using the random forest (RF) machine-learning algorithm for the rapid detection of pretilachlor. SiO2 coatings on red-emitting CdSe/ZnS quantum dots (r-SiO2@QDs) as intermediate light-emitting components are non-selective for pretilachlor, whereas molecularly imprinted layers coated with blue-emitting nitrogen-doped graphene quantum dots (N-GQDS) are selective. Fluorescence images of the Dual-em-MIPs were acquired. The red (R), green (G), and blue (B) color values of the image were analyzed using an RF algorithm, and the classifier was trained using 103 fluorescent images for automatic analyses. Under optimized conditions, an excellent linear relationship between the sensor and pretilachlor was obtained in the range of 0.001–5.0 mg/L (R2, 0.9958). Additionally, the satisfactory recoveries of Dual-em-MIPs ranged between 92.2 % and 107.6 % for the real samples, with a relative standard deviation (RSD) under 6.5 %. The satisfactory recoveries of the RF model based on the fluorescence sensor were 84.2–108.2 % with the RSD under 6.4 %. Overall, the proposed fluorescence sensor based on Dual-em-MIPs and machine learning methods was successfully used to determine pretilachlor in the environment and in aquatic products.

A near-infrared turn-on fluorescent sensor for the determination of copper in mitochondria

Mitochondrial copper is involved in various physiological processes and the dysregulation of mitochondrial copper balance is related to various diseases such as Wilson's disease, Alzheimer's disease and cancer. It is now still a challenge to develop efficient fluorescent sensors for monitoring mitochondrial copper with “turn-on” response due to its inherent paramagnetic quenching effect. In this work, a mitochondria-targeted turn-on fluorescent sensor, CySH, with near-infrared absorption and emission wavelengths, was developed for the selective determination of copper. This probe displays very weak fluorescence at 784 nm due to the photo-induced electron transfer (PET) effect. After the sulfhydryl on the middle position of cyanine is coordinated with copper, the quenching process of PET is inhibited and the fluorescence of probe CySH is turn-on. CySH exhibits high selectivity towards copper and excellent anti-interference ability. Job's plot and high resolution mass spectrometry verified the stoichiometric ratio of 2:1 between CySH and Cu2+. The probe could penetrate the cell membrane well and was utilized to monitor the fluctuation of labile copper in mitochondria. Furthermore, CySH has been successfully used to assess mitochondrial copper variations in copper-overload HepG-2 cells. The proposed feature of the single S-donor might offer a new stratregety for the turn-on fluorescence detection of copper.

Phosphatase-like activity of single-atom Ce[sbnd]N[sbnd]C nanozyme for rapid detection of Al3+

Single-atom nanozymes are a class of nanozymes with attractive enzyme-like activities. They usually mimic oxidoreductases and lack other types of enzyme-like activities. Hence, we verified a single-atom CeNC (SACeNC) nanozyme with an excellent phosphatase-like (PPA-like) activity, which could catalyze the dephosphorylation of inorganic phosphates. Meanwhile, we found that Al3+ could specifically combine with the O atom in its structure to form an Al-O bond, which could inhibit its PPA-like activity. Based on this principle, we have constructed a fast, portable, and efficient fluorescent liquid phase sensor to detect Al3+. The detection time was only 4 min, and the limit of detection (LOD) was 22.89 ng/mL in the linear range of 5–25 μg/mL. This study not only verified that single-atom nanozymes mimic phosphatase activities, but also applied its unique enzyme-like to the field of food safety rapid detection.