Sensitive Fluorescent Sensor Research Articles

A FRET-ICT Dual-Modulated Ratiometric Fluorescence Sensor for Monitoring and Bio-Imaging of Cellular Selenocysteine.

Since the fluctuation of cellular selenocysteine (Sec) concentration plays an all-important role in the development of numerous human disorders, the real-time fluorescence detection of Sec in living systems has attracted plenty of interest during the past decade. In order to obtain a faster and more sensitive small organic molecule fluorescence sensor for the Sec detection, a new ratiometric fluorescence sensor Q7 was designed based on the fluorescence resonance energy transfer (FRET) strategy with coumarin fluorophore as energy donor and 4-hydroxy naphthalimide fluorophore (with 2,4-dinitrobenzene sulfonate as fluorescence signal quencher and Sec-selective recognition site) as an energy acceptor. The sensor Q7 exhibited only a blue fluorescence signal, and displayed two well distinguished emission bands (blue and green) in the presence of Sec with ∆λ of 68 nm. Moreover, concentrations ranging of quantitative detection of Sec of Q7 was from 0 to 45 μM (limit of detection = 6.9 nM), with rapid ratiometric response, high sensitivity and selectivity capability. Impressively, the results of the living cell imaging test demonstrated Q7 has the potentiality of being an ideal sensor for real-time Sec detection in biosystems.

A highly sensitive and selective turn-off fluorescence sensor for Fe3+ detection based on a terbium metal-organic framework

A hydrothermal reaction of 1,3-di(3′,5′-dicarboxylphenyl)benzene (H4ddb) with Tb3+ gave out a metal-organic framework material (Tb-MOF). Tb-MOF emitted green fluorescence, assigned to the characteristic transitions 5D4→7FJ (J ​= ​6–3) of Tb3+. Screening detected metal cations indicated that only Fe3+ can completely quench the fluorescence of Tb-MOF in the twenty optional ions. The sensitivity test of Tb-MOF showed a linear response of I0/I ​= ​55.2061∙CFe3+ + 1.24077 in the CFe3+ range of 3.3 ​× ​10−4-0.033 ​mmol ​L−1 with LOD being 0.936 ​μM. Sixteen metal cations and four anions in the selectivity test did not influence the detection performances of Tb-MOF to Fe3+. The emission intensities of 5D4→7F5 at 545 ​nm of Tb3+ can basically be recovered during a four-time quenching-recovery cycle in the durability test. Tb-MOF is a quantitative turn-off fluorescence sensor to Fe3+ detection with high sensitivity and selectivity, rapid response and a certain durability.

ZnO–SnO2 nanocubes for fluorescence sensing and dye degradation applications

ZnO–SnO2 nanocubes were used as promising material for efficient sensing of p-nitrophenol and faster photocatalytic degradations of dyes like methyl orange (MO), methylene Blue (MB) and acid orange 74 (AO74). ZnO–SnO2 nanocubes were prepared by the facile solution process at 50 °C using Zn(NO3)2·6H2O and SnCl2·2H2O as a precursor in the presence of ethylenediammine. The synthesized material was examined for its morphological, structural, crystalline, optical, vibrational, and compositional studies by using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. FESEM studies revealed the formation of well-defined ZnO–SnO2 nanocubes where the structural examinations revealed the formation of a crystalline tetragonal rutile phase for SnO2 with some crystal sites doped with Zn. The as-synthesized nanocubes were explored for their photocatalytic activities towards three different dye viz. MO, MB, and AO74. Practically, complete degradation of AO74 was seen within 4 minutes of photo-irradiation in the presence of 0.05 g ZnO–SnO2 nanocubes. However, 97.17% and 41.63% degradations were observed for MB and MO within 15 and 60 minutes, respectively. All the dye degradation processes followed the pseudo-first-order kinetic model. Moreover, the as-synthesized nanocubes were utilized to fabricate highly sensitive and selective fluorescent chemical sensor for the detection of p-nitrophenol (PNP). ZnO–SnO2 nanocubes showed a very low detection limit of 4.09 μM for the detection of PNP as calculated according to the 3σ IUPAC criteria. Further, the as-synthesized ZnO–SnO2 nanotubes were found to be highly selective for p-nitrophenol as compared to the other two isomers.

A glycine-functionalized graphene quantum dots synthesized by a facile post-modification strategy for a sensitive and selective fluorescence sensor of mercury ions.

In this work, we have developed a facile method for the synthesis of glycine-functionalized graphene quantum dots (Gly-GQDs) through post-modification of graphene quantum dots with Gly under alkaline conditions. The as-synthesized Gly-GQDs exhibit an excellent blue emission at 444nm, independent of excitation, as well as a high quantum yield (QY) of 35.7%. The Gly-GQDs have a narrow size distribution with an average size of 5.9nm. Moreover, the as-prepared Gly-GQDs showed a better selective and sensitive recognition capability towards mercury ion (Hg2+) in aqueous solutions with a low detection limit of 8.3nM, compared with GQDs and other nitrogen-doped GQDs synthesized through the one-step solvent thermal method. Gly-GQDs are successfully applied for the determination of Hg2+ in real water samples. This work shows a new promising approach for the design and synthesis of desirable GQDs with a given function.

New 3D Cd(II)-based pillar-supported metal − organic framework as fluorescent sensor for sensitive detection of agricultural pesticide pymetrozine

A new three dimensional Cd(II)-based MOF with composition {Cd10(btc)8((bpp)4(Hbpp)4]·2bpp·H2O} (WAU-1) has been synthesized by reaction of Cd(II) salt with 1,3,5-benzenetricarboxylic acid (H3BTC) ligand and 2,5-bis(pyrid-4-yl)pyridine (bpp) co-ligand. The single crystal X-ray analysis showed that the WAU-1 shows 3D pillar-supported framework constructed by bpp co-ligands and [Cd3(btc)2] layers and exhibited typical 6-node pcu-like topology with the point symbol of{412.63}. The sensing studies have been performed on WAU-1 which suggested that the MOF can be used as highly sensitive fluorescent sensor to detect pymetrozine (PYM) a new class of pesticide through fluorescence quenching. Furthermore, the plausible fluorescence quenching mechanism which WAU-1 displayed against PYM and other insecticides has been proposed using theoretical calculations.

Highly fluorescent hematoporphyrin modified graphene oxide for selective detection of copper ions in aqueous solutions

Here, a highly sensitive and selective copper ion (Cu2+) fluorescence sensor is reported. The Hematoporphyrin functionalized Graphene Oxide (HP-GO) fluorescence sensor were synthesized via esterification reaction between Graphene Oxide and Hematoporphyrin (HP). The HP-GO sensor was fully characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electrom Microscopy (SEM), UV–Vis spectroscopy, Transmission Electron Microscopy (TEM), Fluor meter spectroscopy, X-Ray photoelectron spectroscopy(XPS), and Raman spectroscopy measurements. The HP-GO sensor advertised two linear regions over the range of 0–1.18 × 103 nM and 3.93 × 103 to 47.27 nM of copper (II) with detection limit of 54 nM in the aqueous solution. The selectivity of HP-GO for Cu2+ is much higher than that of other metal ions due to the presence of aza macrocyclic ring on the surface of HP-GO which has a high binding affinity with Cu2+. Additionally, the HP-GO shows wide pH viable range (pH 6–10). The effect of other metal ions on the fluorescence intensity of the HP-GO was also studied and other metal ions show a low interference response in the detection of Cu2+. HP-GO sensor manifests advantages of high reproducibility (The quenched fluorescence of HP/GO-Cu can be recovered by EDTA), attractive long term fluorescence stability (>21 days) in water, also remarkable selectivity regarding number of metal ions (Na+, K+, Ca2+, Fe3+, Fe2+, Al3+, Pb2+, Mn2+, Mg2+, Co2+, Ni2+, Cr6+, Cd2+, Hg2+, and Zn2+), low toxicity and can detect Cu2+ in real water samples which acquire well for its promising in environmental applications.

Magneto-Fluorescent Hybrid Sensor CaCO3-Fe3O4-AgInS2/ZnS for the Detection of Heavy Metal Ions in Aqueous Media.

Heavy metal ions are not subject to biodegradation and could cause the environmental pollution of natural resources and water. Many of the heavy metals are highly toxic and dangerous to human health, even at a minimum amount. This work considered an optical method for detecting heavy metal ions using colloidal luminescent semiconductor quantum dots (QDs). Over the past decade, QDs have been used in the development of sensitive fluorescence sensors for ions of heavy metal. In this work, we combined the fluorescent properties of AgInS2/ZnS ternary QDs and the magnetism of superparamagnetic Fe3O4 nanoparticles embedded in a matrix of porous calcium carbonate microspheres for the detection of toxic ions of heavy metal: Co2+, Ni2+, and Pb2+. We demonstrate a relationship between the level of quenching of the photoluminescence of sensors under exposure to the heavy metal ions and the concentration of these ions, allowing their detection in aqueous solutions at concentrations of Co2+, Ni2+, and Pb2+ as low as ≈0.01 ppm, ≈0.1 ppm, and ≈0.01 ppm, respectively. It also has importance for application of the ability to concentrate and extract the sensor with analytes from the solution using a magnetic field.

A core-shell molecularly imprinted optical sensor based on the upconversion nanoparticles decorated with Zinc-based metal-organic framework for selective and rapid detection of octopamine

A sensitive fluorescent sensor for the detection of octopamine (OA) has been established by encapsulating the upconversion nanoparticles (UCNPs) into the metal-organic frameworks (ZIF-8) and incorporating molecularly imprinted polymer (MIP). The presence of ZIF-8 with high specific surface area and strong stability can improve the dispersity and emission intensity of UCNPs in the organic phase. Meanwhile, ZIF-8 membrane reduced the mass transfer resistance and adsorption time of molecularly imprinted polymers. Thus, the final UCNPs@ZIF-8@MIP sensor has exhibited the excellent optical property and the superior selective recognition ability, which was similar to natural receptors. Under the optimum condition, the fluorescence intensity of UCNPs@ZIF-8@MIP increased linearly with the concentration of OA in the range of 0.1−10 mg L−1. Compared with traditional detection methods, the current method with the detection limit of 0.081 mg L−1 would yield double functions of specific recognition and quantitative detection for OA without sophisticated preprocessing. At the spiked concentration levels of 2, 4, 6, 8 mg L−1, the recovery range of OA in beer was 81.75%–90.63% with relative standard deviation (RSD) of 2.56–5.13%.

Multicolor nitrogen dots for rapid detection of thiram and chlorpyrifos in fruit and vegetable samples

The development of sensitive fluorescence sensors and efficient preparation of samples is a challenge in the detection of pesticides in complex samples. In this study, multicolor nitrogen dots (M-Ndots) were synthesised via microwave irradiation at 140 °C for 10 min with 5-amino-1H-tetrazole and p-phenylenediamine as precursors, which have a high fluorescence quantum yield of up to 31%. Furthermore, the M-Ndots were employed as fluorescence sensors for pesticide detection by being combined with a gas membrane separation device, to eliminate the interference from the complex sample matrix. In this process, the M-Ndots were used for sensing thiram and chlorpyrifos through their affinities to Cu2+ and Fe3+, respectively. Because thiram could decompose into volatile CS2, its derivate was sensed using the fluorescence of M-Ndots via a complexation reaction with Cu2+. Chlorpyrifos, due to its volatility, can reduce the Fe3+ ion by inhibiting the activity of acetylcholinesterase, which produces H2O2 to oxidise Fe2+. In a real application, the time consumption for 96 samples was less than 30 min in one run of the gas membrane separation device. The recoveries for thiram and chlorpyrifos ranged from 90.0% to 115.0%, and the analytical results were validated using LC-MS/MS methods, with relative errors ranging from −7.4% to 10.1%.

A Label-free DNA-based Fluorescent Sensor for Cisplatin Detection

Cisplatin, an anti-cancer drug, has been used extensively and has become a “gold standard” treatment for various types of cancer. However, overdosage has serious side effects. Thus, this drug should not be over-administered. The current study presents a label-free but sensitive fluorescent sensor for cisplatin detection based on G-quadruplex (GQ) and fluorescent dye Thioflavin T (ThT). In the absence of cisplatin, ThT binds to GQ, resulting in high fluorescence emission. In the presence of cisplatin, the GQ structure is destroyed after cisplatin–DNA adduct formation, leaving no binding scaffold for ThT, thereby causing a decrease in ThT fluorescence. The amount of cisplatin can be quantified from the changes in ThT fluorescence intensity. Parameters that affect the sensor performance were tested, including pH and concentration of potassium phosphate buffer, type of GQ, number of quartets, loop length, incubation time, and temperature. The sensor provided a linear dynamic range of 10–500 nM with limit of quantification at 10 nM. The sensor was successfully applied to detect cisplatin in urine samples from patients undergoing treatment with high accuracy (recoveries between 74 ± 14 and 112.8 ± 5.0%) and precision (relative standard deviations between 1.15% and 2.12%).

Fluorescence sensor for organophosphorus pesticide detection based on the alkaline phosphatase-triggered reaction

The threat of organophosphorus pesticide (OPP) residue to food safety and human health has caused widespread concern. In this paper, a sensitive fluorescence sensor for OPP detection was constructed based on the alkaline phosphatase (ALP) -triggered in situ reaction. In this method, ALP catalyses the dephosphorylation of the substrate l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AAP) to generate l-ascorbic acid (AA). AA instantly combines with o-phenylenediamine (OPD) to form 3-(1,2-dihydroxyethyl)furo[3,4-b]quinoxalin-1(3H)-one (DFQ), which contains a quinoxaline core skeleton fluorophore and emits a strong fluorescence intensity at 425 nm. The existence of OPPs inhibits the activity of ALP and the production of AA and DFQ. As a result, the fluorescence intensity obviously decreases. Under optimal conditions, the fluorescence intensity linearly depends on the logarithm of chlorpyrifos concentration over a wide range of 20 pg/mL ∼1000 ng/mL with a detection limit of 15.03 pg/mL (S/N = 3), which is lower than the previously reported values. The sensor with its satisfactory accuracy and precision has been successfully applied to the detection of chlorpyrifos in leeks and celery samples with recoveries of 94.5–106.7% and an inter-assay relative standard deviation (RSD) below 11.51%. OPPs can be semiquantitatively determined by the colour changes in ultraviolet light. The superiority of the sensor is due to its visual simplicity without complex fluorescence labelling procedures and costly instruments.

Fluorescence detection of malachite green in fish tissue using red emissive Se,N,Cl-doped carbon dots

Facile detection of malachite green (MG), a toxic dye, in aquaculture is urgently demanded for environment and food safety. Herein, we design a novel fluorescent probe, namely red emissive Se,N,Cl-doped carbon dots (CDs), to accurately determinate MG. CDs are prepared by hydrothermal treatment of selenourea and o-phenylenediamine in HCl solution. This material exhibits excitation-independent dual emissions at 625 and 679 nm, with a high quantum yield of 23.6%. A selective and sensitive fluorescent sensor toward MG is established based on inner filter effect, because both the excitation and emission light of CDs can be strongly absorbed by MG. The fluorescence quenching of CDs is linear to the MG concentration over the range of 0.07–2.50 μM with a low detection limit of 21 nM. Trace-level analysis of MG in fish tissue is successfully explored, demonstrating the great potential of the proposed sensor for MG monitoring in aquatic products.

An anionic polyelectrolyte induced aggregate assembly of Thioflavin-T: A prospective platform for Protamine sensing

Protamine, a polycation, is biologically and medically relevant protein. Protamine exhibits a wide array of functions in biological processes like gene transfer, tissue and organogenesis, cell reproduction, etc. Medically, Protamine is the only clinically approved antidote for Heparin and is routinely used in various surgical interventions, and hence controlling Protamine dosing in patients is very crucial. Taking into account the medical significance of Protamine, designing simple, reliable and sensitive fluorescence sensors is highly desirable. In this work, we propose one such sensitive and reliable fluorescent sensor which is based on a template of dye-polyelectrolyte assembly constituting a molecular rotor dye, Thioflavin-T and an anionic synthetic polyelectrolyte, polystyrene sulfonate. The addition of Protamine, prompts drastic modulations in spectral features of dye-polyelectrolyte assembly which enables sensitive detection of Protamine in aqueous solution. Apart from sensitive detection, our sensing platform aids in highly selective sensing of Protamine compared to other proteins. Moreover, our sensor system is constructed on label-free, inexpensive, commercially available molecules posing as an advantage over other sensor systems which involve laborious synthesis protocols. Most importantly, our sensor template is able to sense Protamine in diluted serum sample, indicating the potential practical utility of our sensor system.

Postmodified Dual Functional UiO Sensor for Selective Detection of Ozone and Tandemly Derived Sensing of Al3.

Development of highly sensitive and selective fluorescent sensors toward hazardous analytes represents great progress in fabricating sensing devices for practical applications. In this work, a highly selective sensor with dual functions has been fabricated via facile postmodification of the UiO-MOF. Butene modified salicylaldehyde is covalently linked to the UiO-66 scaffold via an efficient Schiff-base reaction, resulting in a highly fluorescent ozone sensor of UiO-66-butene. Ozonolysis of the terminal olefin followed by β-elimination could significantly quench the bright blue fluorescence of UiO-66-butene, and linear turn-off detection of ozone in the range of 0-100 μM is well established. The detection is highly sensitive and selective, and a detection limit of 73 nM was calculated. Remarkably, the ozonolysis afforded product could further act as a selective sensor for Al3+ via turn-on fluorescence with a detection limit of 142 nM, representing a second potential sensing function. The chemically selective sequential ozonolysis/β-elimination and remarkable dual functions offer the exclusive detection of ozone over other oxidative species as well as Al3+ over other cations following a tandem process, representing the first example of a direct MOF sensor for dual sensing of ozone and Al3+. This work demonstrates the potential of employing combinatorial principles for fabricating highly selective sensors, and postmodification of MOFs represents a promising facile strategy for developing various functional sensors.

Fe(Ⅲ)-Oxidized Graphitic Carbon Nitride Nanosheets as a Sensitive Fluorescent Sensor for Detection and Imaging of Fluoride Ions

Since excess fluoride ions may lead to a severe health hazard, it is imperative to design a facile and sensitive sensor to detect it in both environmental and biological systems. The reported methods are always subjected to some limits, hampering their practical application. Herein, a two-dimensional turn-on fluorescent sensor, Fe3+-integrated oxidized graphitic-phase carbon nitride nanosheets (Fe-g-CNO), was synthesized via a facile and green method for sensitive detection of fluoride ions. The interactions between the C-N/C = N moieties of oxidized graphitic-phase carbon nitride (g-CNO) and Fe3+ caused fluorescence quenching of g-CNO. Upon addition of F- ions, the fluorescence was recovered through the formation of complex of Fe3+ and F-. The limit of detection of the sensor was 1 × 10-6 M. Furthermore, this probe could be used as an imaging agent of fluoride ions in living cells and teeth for diagnosis of dental fluorosis. The work provides a safe and efficient platform for further environmental and biomedical uses.

A Vanillinyl‐Hydrazone Schiff Base: Recognition of Mg2+, Zn2+, Cd2+ and I− by Turn‐On Fluorescence Method

AbstractVanillinyl‐hydrazone Schiff base, 2,6‐Bis‐[(2‐hydroxy‐3‐methoxy‐benzylidene)‐hydrazonomethyl]‐4‐methyl‐phenol (PHV) is characterized by spectroscopic techniques and serves as selective and sensitive fluorescence sensor at different emission wavelength for Zn2+ (λem, 546 nm), Cd2+ (λem, 567 nm) and Mg2+ (λem, 625 nm) in DMSO/H2O medium (9 : 1, v/v) in presence of large number of available cations. The probe also displays selective turn‐on fluorescence sensitivity to I− (λem, 635 nm) in THF medium. Density Functional Theory (DFT) computation techniques are used to explain some of the obtained experimental observation.

Novel 2‐hydroxynaphthalene‐based fluorescent turn‐on sensor for highly sensitive and selective detection of Al3+ and its application in imaging in vitro and in vivo

Excessive aluminum exposure in the human body has been held responsible for multiple adverse effects, and existing data underscore the significance of aluminum detection in environmental and biological systems. Developing high‐performance Al3+ fluorescent chemosensors can revolutionize our understanding of the physiological and pathological processes of Al3+ ions. Herein, we reported a highly sensitive and selective Schiff base fluorescence sensor, bis‐NAPPD (1,1'‐((1E,1'E)‐(pyridine‐2,3‐diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen‐2‐ol)), which can recognize Al3+ ions and exhibits a remarkable turn‐on dual emission response (by ~23 fold) with a low nanomolar level detection limit (1.67 × 10−8 M) in methanol. Furthermore, the binding behavior and the turn‐on fluorescence probing mechanism of bis‐NAPPD were illustrated in detail by UV–vis titration, 1H NMR, and ESI‐MS spectroscopy as well as density functional theory calculations. Notably, bis‐NAPPD showed great potential for tracing Al3+ distribution in cells and living zebrafish larvae, and can also be applied in the fluorimetric detection of aluminum in sucralfate tablets with good precision and satisfactory accuracy, which may represent a promising Al3+ probe in bioimaging and biomedical applications.

New three-dimensional Zn(II)/Cd(II)-based coordination polymers as luminescent sensor for Cu2+

Solvothermal reactions of the bifunctional 2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid (H2L), transitional metal Zn(II) and Cd(II) cations afford two coordination polymers, namely, [Zn(L)(H2O)]n (1), and [Cd2L2]n (2), (L = 2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid). Their structures and properties have been determined by single-crystal and powder X-ray diffraction analyses, IR spectra, elemental analyses, thermogravimetric analyses (TGA). Complex 1 exhibits an interesting 3D framework. The host network of complex 2 displays an unusual 3D network. Topology analyses reveal that 1 can be simplified as a 10-connected uninodal net with a point symbol of (312.414.519), and 2 adopts a 16-connected uninodal net with a point symbol of (339.476.55). In addition, luminescent investigations suggested that 1 and 2 exhibit highly selective and sensitive for Cu2+ over other cations with high quenching efficiency Ksv value 4.01 × 103 L·mol−1, 8.49 × 103 L·mol−1, respectively. The experimental result provides a helpful perspective for the design of sensitive fluorescent recognition sensors for Cu2+.

Phenothiazine and BN-doped AIE Probes Integrated Fluorescence Sensor Array for Detection and Discrimination of Nitro Explosives

Abstract Highly effective sensing of nitro explosives plays an extremely important role in homeland security and counter-terrorism. In this work, a BN-doped aggregation induced emission (AIE) probe SN-1 was synthesized and subsequently characterized. The probe was then exposed to DNT and TNT, which resulted in formation of intermolecular hydrogen bonds between the probe and the two nitro explosives, and thus fluorescence quenching response was achieved. In addition, an electron rich phenothiazine probe SN-2 was also prepared to probe the response to the nitro explosives via photo-induced electron transfer. The two probes were combined to construct a fluorescence sensor array for the successful distinction of five nitro explosives. This reliable and sensitive fluorescence sensor array held a good potential for homeland security and environmental management.

A highly sensitive fluorescent probe for tracking intracellular zinc ions and direct imaging of prostatic tissue in mice

A highly sensitive fluorescent sensor ZnDN was designed, synthesized and used for tracking intracellular zinc ions in various living cells and direct imaging of prostatic tissue in mice. ZnDN was prepared from the heterocyclic-fused naphthalimide fluorophore, and the zinc receptor, N,N-bis(2-pyridylmethyl)ethylenediamine (BPEN). Upon addition of Zn2+ to the solutions of ZnDN, a remarkable fluorescence enhancement was observed, which could be attributed to the photo-induced electron transfer (PET) mechanism. Since ZnDN exhibited high sensitivity toward Zn2+ in phosphate buffer solution, with a limit of detection of 4.0 × 10−9 mol/L, it was further applied for the imaging of exogenous and endogenous Zn2+ in different living cells. Living cells imaging experiments suggested that ZnDN could image the changes of intracellular free zinc ions, and could be used for two-photon imaging. Moreover, flow cytometry suggested that ZnDN could distinguish cancerous prostate cells from normal cells. Animal experiments indicated that ZnDN had the potential in imaging prostate tissue in vivo.