Fluorescence Sensor For Detection Research Articles

A novel thiazole-based covalent organic framework as turn-off fluorescent sensor for detection of aniline and triethylamine in liquid and vapor phase

Due to the diverse chemical structures and varying basicity of amines, the development of rapid, portable, and reversible methods for the selective recognition of trace organic amines in the environment remains a challenge. Herein, a novel recyclable and selective turn-off fluorescent sensor for organic amines detection based on covalent organic framework (COF) was developed. As-synthesized COF, TAPB-BTDD exhibits good crystallinity, high chemical stability and strong fluorescence, which can selectively recognize triethylamine (TEA) and aniline in both liquid and vapor phase. The COF material demonstrates impressively low LOD values for aniline and triethylamine in solution, estimated to be 27 nM and 170 nM, respectively. Moreover, when detecting aniline and triethylamine vapors, the calculated LOD values are 20.1 ppb and 106.4 ppb, respectively. In addition, TAPB-BTDD showed basically unchanged emission intensities and rapid response to the amines after ten recycling tests, suggesting that the COF has high stable recycle repeatability. The combination of experimental analysis and density functional theory (DFT) calculations demonstrates that the unique fluorescence-quenching response of TAPB-BTDA can be attributed to the photoinduced electron transfer (PET) between the amines and the COF. This COF-based sensor offers a promising solution for the accurate and reliable detection of organic amines in various environmental settings.

A novel multifunctional fluorescent capillary-based sensor for simultaneous monitoring of pH, O2 and CO2

A fluorescent capillary sensor for detecting the bioanalytically and biologically relevant analytes pH, O2, and CO2 has been designed. The sensor is based on single capillary tube with 2 mm inner diameter, which is simultaneous doped with emissive O2-sensitive indicator Ru(dpp)3(PF6)2 (RuDP), pH-sensitive and CO2-sensitive indicator 8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt (HPTS). The multifunctional sensor can be excited at the same wavelength and realize multi-parameter optical monitoring at the different sensing position. Studies in phosphate-buffered solutions display the excellent feasibility of the capillary sensor for fluorescence detection of pH, O2, and CO2. Overall, the multifunctional capillary sensor exhibits great potential in real-time blood gas analysis, and clinical application of multi-parameter biological detection.

The complex of Schiff base and gallium as a fluorescent sensor for detection of Rh3+ and Cr3+

A new fluorescent probe (EQTPC[Ga3+]) based on a Schiff base (E)-N'-(3-ethoxy-2-hydroxybenzylidene)-1-(quinolin-8-yl)-5-(thiophen-2-yl)-1H-pyrazole-3-carbohydrazide (EQTPC) and gallium(III) was designed and synthesized for detection of chromium(III) and rhodium(III). EQTPC exhibited “turn-on” fluorescent response towards Ga3+, and the complex EQTPC[Ga3+] was furthermore applied for detection of Rh3+ and Cr3+ through “turn-off” fluorescent response. Optical activity of EQTPC[Ga3+]-Cr3+ was reversible when treated with EDTA. The detection limits of EQTPC for Ga3+ and EQTPC[Ga3+] for Rh3+and Cr3+ were 6.08 × 10-8 M, 9.72 × 10-8 M and 1.27 × 10-8 M, respectively. According to the analysis of 1H NMR, 13C NMR, MS and FTIR spectra, the EQTPC and target ions tended to 1: 2 complexes.

Cellulose/amylose derivatives bearing bulky substituents as reversible fluorescent sensors for detection of Fe3+

Two novel cellulose and amylose derivatives bearing bulky tris(2-benzothienylformate) pendants (Cel-3 and Amy-3) were expeditiously prepared by one-step esterification. The fluorescent sensing performance of six polysaccharide derivatives, including Cel-3/Amy-3, and other four previously prepared benzothienyl- or benzofuranyl-phenylcarbamates of cellulose and amylose (Cel-1/Amy-1, Cel-2/Amy-2), were carefully evaluated using eight metal ions, including Co2+, K+, Na+, Li+, Hg2+, Ni2+, Ca2+ and Fe3+. All six derivatives exhibited excellent fluorescence quenching property to Fe3+ ions with high sensitivity and selectivity. Especially, the limit of detection of Amy-2 with benzofuranylphenylcarbamates for Fe3+ was 3.0 μM, much lower than the maximum contaminant level for Fe3+ in the drinking water. Additionally, the six bulky derivatives displayed the interesting fluorescence “turn-off” and “turn-on” observation, indicating a desirable reversibility for Fe3+ detection. The high anti-interference ability was also observed for detection of Fe3+ on the benzothienyl/benzofuranyl derivatives of cellulose and amylose in the combined system containing Co2+, K+, Na+, Li+, Hg2+, Ni2+ and Ca2+. It suggested that the obtained polysaccharide derivatives with bulky chromophores possessed good potentials for detection of Fe3+ as high-efficient fluorescent sensors in diverse applications. The sensing mechanism for detection of Fe3+ was further proposed based on the Stern-Volmer plots and fluorescence titration analysis.

The first fluorescent sensor for the detection of closantel in meat.

Closantel is widely used in the management of parasitic infestation in livestock, but is contraindicated in humans due to its high toxic to human retina. Thus, development of a fast and selective method for the detection of closantel residues in animal products is highly needed yet still challenging. In the present study, we report a supramolecular fluorescent sensor for closantel detection through a two-step screening process. The fluorescent sensor can detect closantel with a fast response (<10s), high sensitivity, and high selectivity. The limit of detection is 0.29ppm, which is much lower than the maximum residue level set by government. Moreover, the applicability of this sensor has been demonstrated in commercial drugs tablets, injection fluids, and real edible animal products (muscle, kidney, and liver). This work provides the first fluorescence analytical tool for accurate and selective determination of closantel, and may inspire more sensor design for food analysis.

Two anthracene-based zirconium metal–organic frameworks with fcu and hcp topologies as versatile fluorescent sensors for detection of inorganic ions and nitroaromatics

Two anthracene-based zirconium metal–organic frameworks (UiO-68-AN-fcu and UiO-68-AN-hcp) with blue emission were synthesized by the solvothermal reaction of ZrCl4 with anthracene-based ligand 4,4′-(9,10-anthracenediyl)dibenzoic acid. The two MOFs inherited the luminescence properties of anthracene-based ligand and exhibited different topologies due to the change of connection mode of Zr-O clusters. The two stable anthracene-based zirconium MOFs served as luminescent sensors for selectively detecting 2-nitrophenol, Fe3+ and Cr2O72−. UiO-68-AN-hcp with flower morphology exhibited stronger quenching effect for 2-nitrophenol, Fe3+ and Cr2O72− by comparing to UiO-68-AN-fcu. Adsorption tests, fluorescence lifetime and spectroscopy studies demonstrated that the fluorescence responses of MOFs for analytes can be primarily attributed to the dynamic quenching mechanism involving energy and electron transfer. These results revealed that the combination of luminescent anthracene-based ligand and Zr-O clusters is a feasible strategy to construst MOFs-based fluorescent sensors.

L-Glutathione modified graphitic carbon nitride quantum dots: An ultrasensitive fluorescent sensor for detection of Pb2+ in water

A facile, sensitive, and selective fluorescence detection method for Pb2+ ions is designed using L-Glutathione (GSH) modified graphitic carbon nitride quantum dots (GSH@g-C3N4 QDs). A carbodiimide-activated coupling reaction is used to bind GSH onto g-C3N4 QDs. When excited at 340 nm, the as-obtained passivated quantum dots exhibit strong blue emissions at 420 nm. With a relative quantum yield of 27%, the system demonstrates exceptional stability against ionic strength and photobleaching. Additionally, it is discovered that the fluorescence emission of the sensor is selectively quenched in the presence of Pb2+ ions. The limit of detection (LOD) for Pb2+ is measured to be 0.025 µM in a linear range of 0.01 µM-0.1 µM. The average lifetime calculations from the lifetime decay experiment along with UV–vis. absorption studies suggest that the quenching pattern follows a static quenching mechanism. Finally, the system is used in real water samples to detect Pb2+ with a substantial recovery percentage greater than 90%.

A highly selective “on–off” fluorescent sensor for detection of Fe3+ ion in protein and aqueous media: Synthesis, structural characterization, and computational studies

We describe herein the design and synthesis of a smart PGA chemosensor characterized by various techniques viz., FT-IR, UV–visible, 1H NMR, 13C NMR, Mass spectroscopy, and single crystal X-ray diffraction studies. The X-ray crystal analysis revealed that the PGA chemosensor crystallized in the orthorhombic crystal system with P212121 space group. The photophysical properties of the synthesized PGA chemosensor were examined by employing absorption and fluorescence spectral analysis. PGA revealed turn-on sensing responses towards the selective recognition of Fe3+ over other metal ions via CN isomerization processes. PGA also shows reversible effects upon the addition of EDTA. The 2:1 binding stoichiometry was calculated using Job’s plot and the value of detection limit was found to be 0.265 × 10-5 M, which is far lower than the permitted limit for drinking water according to WHO guidelines. The sensing mode of PGA towards Fe3+ was explored by employing FT-IR and 1H NMR studies. Density Functional Theory (DFT) studies, were employed which closely agreed with the experimental results. The PGA chemosensor has been successfully used to detect Fe3+ in various water samples and BSA medium. Furthermore, confocal imaging studies were examined, which supports the sensing ability of PGA for detection of Fe3+ in aqueous and protein medium.

BODIPY-based fluorescent sensors for detection of explosives

The detecting and screening of explosives has become a global consideration in dealing with potential terrorism threats and the misuse of high explosives. Several detection techniques have been developed, but their disadvantages include the requirement of expensive equipment, complicated pre-treatment, and prolonged testing. So far, fluorescence-based sensors have been of great interest as they overcome the limitations of other techniques. BODIPY, which is a fluorophore, shows excellent fluorescence features, and it can be used as a sensor material for explosives detection. However, to date, BODIPY-based explosive sensors have not been explored in detail. This work reviews the recent developments on explosive sensors based on BODIPY and its analogs.

CdS Semiconductor Quantum Dots; Facile Synthesis, Application as Off Fluorescent Sensor for Detection of Lead (Pb2+) Ions and Catalyst for Degradation of Dyes from Water.

The CdS quantum dots (QDs) were prepared by rapid, one-pot, and novel photochemical method, which used Thioglycolic acid (TGA) molecules as both stabilizer and sulfur source. The structure and morphology of the prepared CdS QDs were characterized by different analyses such as XRD, FT-IR, Raman, EDS, TEM, PL, and absorption. In this work, was used of CdS QDs as off fluorescence sensor for rapid and simple detection of lead (Pb2+) ions in water. The PL intensity of CdS QDs in the presence of lead ions decreased gradually and in the presence of 100μM lead ions, photo emission completely quenched. The photocatalyst performance of CdS QDs was investigated by methylene blue (MB), methylene orange (MO), and rhodamine b (RB) pollutant dyes under both UV and sun lights. The obtained results showed that CdS QDs had excellent photocatalyst activity with dyes under UV light and 94.9% of MO dye, 94.4% of RB dye, and 81.2% of MB was degraded after 60min UV irradiation. For understanding about which parameter have a key role in the photodegradation process of MO by CdS QDs under UV illumination, several radical scavengers were used, and results showed that holes have a key role in the degradation process.

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.

Glucosaminic acid-functionalized graphene quantum dots for sensitive detection of lactose in living cells and real food samples

The design of a nonenzyme sensor for lactose imaging in living cells is still a challenge nowadays. Enlightened by the saccharide–saccharide recognition at the cell surface, we prepared a graphene quantum dots–glucosaminic acid (GQDs–GA)-based fluorescent sensor for detection of lactose in living cells with high selectivity and sensitivity. GA acts as a receptor for lactose, while GQDs acts as a fluorescence signal transducer. Upon lactose addition, the fluorescence peaks at 315 and 429 nm were significantly enhanced owing to the blocking of photoinduced electron transfer. The interaction of the GQDs–GA sensor with lactose was mainly governed by the amide•••OH and OH•••π hydrogen bonding, supported by 1H NMR and density functional theory (DFT) calculations. A good linear relationship with the concentration of lactose was obtained over the range of 9.9 − 142.9 μM with a detection limit of 0.35 μM. The proposed sensor was used to detect lactose in real samples (tap water, milk, and honey) with a recovery range of 100.16–103.32%. More importantly, the GQDs–GA sensor can be used to track lactose in living cells. This work provides new insights into development of nonenzyme-based biosensor for single saccharide.

Rice straw derived cellulose nanofibers modified with L-histidine for ultra-trace fluorometric assay of Cr(VI) and Hg(II) in aqueous medium

Through this study, an effort has been made to eliminate the problems of rice straw burning and pollution due to heavy metals by utilizing cellulose nanofibers (CNFs) derived from rice straw to develop effective fluorescent sensors for detection of chromium Cr(VI) and mercury Hg(II), concurrently. CNFs were modified using L-histidine (CHIS) to yield cellulosic fluorophore, not reported hitherto. Characterization using X-ray Powder Diffraction (XRD), Field emission scanning electron microscopy (FESEM) and Thermogravimetric analysis (TGA), indicated partial impairment of crystalline structure of cellulose with conversion to CHIS, however the sensor was thermally more stable as 40% mass residue remained even after 700 °C. Fluorescence response exhibited substantial quenching with Cr(VI) and Hg(II) ions, with detection limits of 2.236 nM and 3.97 nM, respectively. The XPS studies established strong interactions of CHIS with Hg(II) ions via imine groups and Cr(VI) ions with imine as well as amine group on CHIS resulting in substantial quenching. Further, when excited at different wavelength under fluorescence microscope, CHIS indicated suppression of fluorescence effect with adsorption of heavy metal ions. The sensor was highly selective, stable with time and pH with excellent usability up to 4 cycles. Thus, CHIS present a facile and robust platform for simultaneous detection and real time monitoring of Hg(II) and Cr(VI) metal ions.

Selective detection of aspartic acid in human serum by a fluorescent probe based on CuInS2@ZnS quantum dots

The importance of amino acids identification in biological systems has created expectation to develop a sensitive method for their detection. In this work, an efficient core-shell fluorescent quantum dots (QDs) probe based on CuInS2 (CIS) core and ZnS shell with the formula of CIS@ZnS QDs were synthesised and characterised by FT-IR, UV–Vis, TEM and DLS techniques. The probe was used for detection of Aspartic Acid (Asp) in an aqueous media. The probe shows a remarkable fluorescence response toward Asp over the other amino acids such as valine (Val), glycine (Gly), phenylalanine (Phe), leucine (Leu), alanine (Ala), serine (Ser), isoleucine (Iso), threonine (Thr), methionine (Met), Glutamic acid (Glu), histidine (His), arginine (Arg), cysteine (Cys), asparagine (Asn), glutamine (Gln), citrolline (Cit), sarcosine (Sar) and ornithine (Orn) the fluorescence intensity quenches significantly upon addition of Asp in an aqueous media. The CIS@ZnS QDs probe showed a selective and sensitive response by fluorescence quenching toward Asp in the concentration range of 8.3 × 10−7 M to 3.3 × 10−4 M with the detection limit of 7.8 × 10−8 M. The application of the sensor in determination of Asp in real human serum sample was also investigated. Based on our library search, the all reported fluorescent sensors for detection of Asp, either show a remarkable sensitivity to Glu acid. Luckily, this is the first presented optical probe able to detect just Asp from the solutions containing various amino acids.

A new “off-on-off” Schiff base from quinoline and thiophene as a fluorescent sensor for sequential monitoring Ga3+ and Pd2+

A Schiff base (E)N'-(2-hydroxybenzylidene)-1-(quinolin-8-yl)-5-(thiophen-2-yl)-1H-pyrazole-3-carbohydrazide (N1) was designed and synthesized from 1-(quinolin-8-yl)-5-(thiophen-2-yl)-1H-pyrazole-3-carbohydrazide and salicylaldehyde. It was used as highly selective and sensitive fluorescent sensors for detection of Ga3+ in DMF/H2O solution with an obvious color change. The new formed complex N1-Ga3+ could recognize Pd2+ with the quenching of fluorescence. The limit of detection (LOD) for Ga3+ and Pd2+ were 1.4 × 10−8 M and 6.4 × 10−7 M, respectively. The stoichiometry of N1 with Ga3+and Pd2+ were both confirmed to be 1: 2. Monitoring Ga3+ and Pd2+ in tap-water was well performed. Test paper was made to detect Ga3+ effectively.

Microwave synthesis of blue emissive carbon dots from 5-sulpho anthranilic acid and 1,5-diphenyl carbazide for sensing of levocetirizine and niflumic acid

In this work, water soluble carbon dots (CDs) were synthesized by using 5- sulpho anthranilic acid (SAA) and 1,5-diphenylycarbazide (DPC) as precursors via microwave-assisted method and named as “SD-CDs”. We studied the effect of SAA and DPC molar ratio (1:3, 2:2 and 3:1) for the preparation of blue fluorescent CDs, showing the best emission properties at molar 3:1 ratio of SAA and DPC. The as-prepared SD-CDs emit bright blue color under UV light at 365 nm, and exhibit emission peak at 392 nm when excited at 319 nm. The as-synthesized SD-CDs act as a fluorescent sensor for detection of levocetirizine and niflumic acid through the fluorescence “turn-on–off” mechanism. The developed probe exhibited good linearity in the concentrations (levocetirizine − 1.0–100 µM and niflumic acid − 0.5–100 µM) with detection limits of 3.92 nM and 0.19 µM for levocetirizine and niflumic acid, respectively. Importantly, the developed analytical method was successfully used for the detection of levocetirizine in tablets and niflumic acid in biofluids of human (serum, plasma and urine), showing good recoveries from 97 to 99 %. Thus, this SD-CDs-based fluorescence method has the potential for levocetirizine and niflumic acid assays in biological and pharmaceutical samples.

Construction of continuously enhanced fluorescent sensor for detection of glutathione in normal and cancer cells

In this paper, water-soluble cysteamine (CA)-capping CdSe quantum dots (CA-CdSe) could be used as a continuous fluorescent sensor. The CA-CdSe QDs can respond to Ag+ with a detection limit of 54.1 nM. Interestingly, CA-CdSe quantum dots combined with Ag+ to generate a new nano-fluorescence sensor-Ag+ modified CA-CdSe QDs (Ag+@CA-CdSe). Ag+@CA-CdSe can detect glutathione (GSH) with good sensitivity and anti-interference performance. The detection limit of Ag+@CA-CdSe fluorescenct sensor for GSH is as low as 0.74 μM. In addition, the novel nano-fluorescent sensor Ag+@CA-CdSe exhibited good cell permeability and was successfully applied to detect exogenous and endogenous GSH concentrations in cells. It could distinguish cancerous and normal cells by in vitro cell fluorescence imaging.

A novel colorimetric and “turn-on” fluorescent sensor for selective detection of Cu2+

In this work, a new highly selective and sensitive fluorescent sensor for detecting Cu2+ was developed based on rhodamine fluorophore. It displayed strong fluorescence “turn-on” effect upon addition of Cu2+, and possessed the function of naked eye recognition. The fluorescence enhancement also enabled the sensor to quantitatively analyze Cu2+ due to the formation of a stable 1:1 metal–ligand complex in a short time, and the complex possesses relatively good pH stability. In addition, the density functional theory calculations were adopted to investigate the molecular orbitals as well as the spatial structure. Simultaneously, the cell imaging and zebra fish experiments provided a broader application prospect in biological system.

Coumarin-Picolinohydrazone derived Schiff base as fluorescent sensor(OFF-ON) for detection of Al3+ ion: Synthesis, Spectral and theoretical studies

New coumarin based Schiff base (7MIZ) was synthesized and characterized by various spectral techniques and the true nature was established by X-ray single crystal studies. The probe (7MIZ) acted as fluorescent sensor for detection of Al3+ ion among different metal ions (chloride salts) with high selectively. There was a drastic enhancement in the emission intensity at 482 nm showed fluorescence turn ‘ON’ behavior of the probe when it interacted with Al3+ ion which may be due to CHEF (chelation enhanced fluorescence) effect that inhibited the PET (photo-induced electron transfer) mechanism. Further, Job's plot, binding constant value, LOD value, DFT studies established the interaction between probe (7MIZ) andAl3+ ion and MTT assay studies were carried out for the probe (7MIZ) and Al3+ ion in Breast cancer cell line (MDA-MB-231).

A label-free G-quadruplex and ThT mediated fluorescent sensor for detection of Cu2+ from water samples

A facile and label-free detection method based on the formation of the G-quadruplex structure of Thioflavin T and a DNA sequence was developed for rapid and sensitive detection of copper (Cu2+) ion. The DNA sequence with many guanine (G) repeats has the potential to form a G-quadruplex structure and exhibits high selectivity to Cu2+. ThT promotes the formation of the G-quadruplex structure resulting in high fluorescence intensity because of its fluorescence molecular rotor characteristic. As opposed to, when the DNA sequence binds to its target in the presence of Cu2+, conformational changes occur, resulting in ThT dissociation and a substantial decrease in fluorescence intensity. By virtue of this change, unlabeled, low-cost, sensitive, and selective detection of Cu2+ was achieved and not interfered by many other ions. The proposed method has high sensitivity and selectivity, with a detection limit of 30.7 nM, allowing it to directly measure Cu2+ in contaminated water samples in a wide linear range from 0.1 to 100 µM with a high recovery rate.