Isomeric fluorescence sensors for wide range detection of ionizing radiations

In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.

CdTe quantum dots as fluorescence sensor for the determination of vitamin B6 in aqueous solution

A novel, rapid and simple CdTe quantum dots （QDs） based technology platform was established for selective and sensitive determination of vitamin B6 in aqueous solution. It can perform accurate and reproducible quantification of vitamin B6 in pharmaceutical with satisfactory results.

Terpyridine-derived Zn^(2+) Selective Fluorescence Sensor: Ratiometric Fluoroionophoric Behavior Study

A sensitive and selective zinc ion ratiometric fluorescence sensor has been synthesized and characterized. This material displays dual fluorescence. After the material was bonded to a closed-shell metal ion, such as Zn2＋, the recovery of the local excited fluorescence of the material-Zn2＋ complex, largely at the expense of the intramolecular charge transfer fluorescence, is consistent with the difference between selected orbital transitions of the free dye and the metal-chelated complex. For instance, the contribution of the πtpy→πtpy, transition becomes more prominent. This is also consistent with the results of the fluorescence decay behavior, measured via a time-correlated single photon counting setup. In contrast, the corresponding open shell Ni2＋ -bound complex quenches both kinds of photoluminescence, due to spin-orbit coupling.

Anthracylmethyl Benzoazacrown Ether as Selective Fluorescence Sensors for Zn^(2+)

A new benzoazacrown ether fluorescence sensor was synthesized with 9-anthrylmethyl chloride and benzoaza-15-crown-5 in CH3CN, which particularly shows a strong affinity for Zn2+. Its fluorescence quantum yield increase more than one order of magnitude and a red shift could be noticed when passing from the apolar to the polar solvent.

Carbon Dots as“On–Off–On”Fluorescence Sensors for Selective and Consecutive Detection of 4-Nitrophenol and Cerium(IV)in Water Samples

An“on–off–on”fluorescence sensor was designed for rapidly and consecutively detecting 4-nitrophenol and cerium(IV)without the use of any labeling materials.The yellow carbon dots were synthesized by a simple one-step hydrothermal approach,and various techniques were applied to investigate the morphology,structure,and optical properties of the carbon dots.Under the optimal experimental conditions,4-nitrophenol rapidly quenched the fluorescence of carbon dots as a result of the inner filter eff ect(IFE).The fluorescence intensity of carbon dots was linear with the concentration of 4-nitrophenol(1–150μmol/L)and the limit of detection was 0.32μmol/L.The fluorescence was gradually recovered as the cerium(IV)concentration(0.5–100μmol/L)increased in CDs/4-NP,and the limit of detection was 0.16μmol/L.The sensor showed good selectivity and demonstrated high accuracy for the analysis of 4-nitrophenol and cerium(IV)in actual water samples.

Bi-ortho-Carborane Unit-Riveted Perylene Monoimides:Structure-Tuned Optical Switches for Electron Transfer and Robust Thin Film-Based Fluorescence Sensors

Innovative design of sensing fluorophores possessing superior photophysical properties,porosity,and packing-resistance structures is pivotal for high performance film-based fluorescent sensors.Herein,PDCB,a perylene monoimide(PMI)derivative incorporating large spatial phenyl-carborane was synthesized and found to exhibit unexpected photophysical properties.The structurally bent PDCB exhibits not only PMI-like emission but also a red-shifted emission.In sharp contrast,PMI-CBH,a linear PMI derivative,exhibits only PMI-like emission.Furthermore,upon local excitation,PDCB undergoes a photoinduced electron transfer(PET)between PMI and phenylcarborane,resulting in a charge-transfer state.Two other PMI derivatives,PCB and PDCBP,showed a similar phenomenon.The PET rate is in the order of PCB(48 ps^(-1))>PDCB(163 ps^(-1))>PDCBP(815 ps^(-1))in toluene,which decreases with increasing steric hindrance,inferring structure reorganization prior to the PET process.As expected,a fabricated PDCB-based sensor showed excellent performance in acetone sensing.

A flexible and superhydrophobic upconversionluminescence membrane as an ultrasensitive fluorescence sensor for single droplet detection

A Ln^(3+)-doped(Yb^(3+),Tm^(3+)or Yb^(3+),Er^(3+)co-doped)NaYF4 nanoparticle/polystyrene hybrid fibrous membrane(HFM)was fabricated using an electrospinning technique.The HFM shows upconversion luminescence(UCL),flexibility,superhydrophobicity and processability.The UCL membrane can be used as a fluorescence sensor to detect bioinformation from a single water droplet(~10μl).Based on the fluorescence resonance energy transfer,the detection limits of this sensor can reach 1 and 10 ppb for the biomolecule,avidin,and the dye molecule,Rhodamine B,respectively,which are superior to most of the fluorescence sensors reported in previous works.After the fluorescence detection,the target droplet was easily removed without residues on the UCL membrane surface due to its superhydrophobic property,which exhibits an excellent recyclability that cannot be achieved by traditional liquid-based detection systems.

Comparison of Two Rhodamine-Polyamine Polystyrene Solid-phase Fluorescence Sensors for Hg(Ⅱ) Detection Based on Theoretical Calculation

Two novel rhodamine-based polystyrene solid-phase fluorescence sensors PS-PA-Ⅰ and PS・PA-Ⅱ with different lengths of polyamines were synthesized for Hg(Ⅱ)determination.Thedetection mechanism involving the Hg(Ⅱ)chelation-induced spirocycle open of rhodamine was proposed with the aid of theoretical calculation.The stronger N—Hg bond and the longer polyamine chain in PS-PA-Ⅱ led to a better selectivity,much higher and more quickly fluorescence response to Hg(Ⅱ).

Switch-on fluorescence sensor for ascorbic acid detection based on MoS2 quantum dots-MnO2 nanosheets system and its application in fruit samples

In this work,molybdenum disulfide quantum dots（MoS2 QDs） were firstly prepared by hydrothermal method using sodium molybdate and glutathione as precursors,and applied in ascorbic acid detection.When joining MnO2 nanosheets into MoS2 QDs solution,they produced an obvious fluorescence quenching,which should be due to inner filter effect（IFE）.Meanwhile,the fluorescent probe was formed,Interestingly,we found that this quenching phenomenon disappeared with the addition of ascorbic acid,In other words,the fluorescence gradually restored.This recovery phenomenon is mainly due to the reduction effect of ascorbic acid for MnO2 nanosheets.Under the optimum conditions,the limit of detection（LOD） of 39 nmol/L for ascorbic acid was achieved with a linear range of 0.33-5.00 μmol/L.The repeatability was better than 5.0% for ascorbic acid in both standard and fruit samples（n = 3）.Moreover,the as-fabricated fluorescent sensing system was successfully employed to detect the ascorbic acid levels in hawthorn and jujube with satisfactory results.

A Novel Highly Selective“Turn-On”Fluorescence Sensor for Silver Ions Based on Schiff Base

A novel optical chemical sensor L was designed and synthesized for the determination of silver ions.The sensor L was derived from 1-naphthaldehyde and 3,4,5-tris(hexadecyloxy)benzohydrazide.The sensor L shows high sensitivity and selectivity for Ag+detection in comparison to other metal cations(Mg^(2+),Ca^(2+),Al^(3+),Cr^(3+),Fe^(3+),Co^(2+),Ni^(2+),Cu^(2+),Zn^(2+),Cd^(2+),Hg^(2+),Pb^(2+))and has no significant response to other common metal cations.Upon addition of Ag+,the fluorescent emission of the sensor L was enhanced dramatically but other metal cations had no same response.The detection limit for Ag+was 1.2×10^(−7) mol/L.Therefore,the sensor L is useful for Ag+detection with some advantages including sensitivity,selectivity,simplicity and low-cost.

A Fluorescence Optical Fiber Sensor for Amrinon Using a New Oxazole Compound

A new oxazole compound, 1,4 bis(naphtho[1,2 d][1,3]oxazol 2 yl)benzene(BNOB) was synthesized and incorporated into a thin plasticized polymeric membrane for sensing Amrinon. The sensor exhibits a linear response to Amrinon in the range of 7 98×10 -7 —1 52×10 -4 mol/L at pH 3 28—4 04. The response mainly originates from the Primary Inner Filter Effect, which causes a decrease in the fluorescence intensity of the sensor membrane. The distinct advantages of the proposed sensor are of full reversibility, high sensitivity and selectivity as well as short response time(<1 min), indicating that the sensor can be used to monitor Amrinon in serum samples.

1-Pyrenecarboxaldehyde thiosemicarbazone:A novel fluorescent molecular sensor towards mercury(Ⅱ) ion

A novel and simple fluorescent molecular sensor,1-pyrenecarboxaldehyde thiosemicarbazone（Hpytsc）,was synthesized.Its higher sensitivity and selectivity to mercury（Ⅱ） ion were studied through absorption and emission channels.The UV-vis spectra show that the increasing mercury（Ⅱ） ion concentrations result in the decreasing absorption intensity.The fluorescence monomer emission of Hpytsc is enhanced upon binding mercury（Ⅱ） ion,which should be due to the 1：1 complex formation between Hpytsc and metal ion.

High sensitivity detection of baicalein by N,S co⁃doped carbon dots and their application in biofluids

In this work,p⁃phenylenediamine and L⁃cysteine were used as raw materials,and water⁃soluble N,S co⁃doped carbon dots(N,S⁃CDs)with excellent performance were prepared through a one⁃step solvothermal method.The morphology and structure of N,S⁃CDs were characterized by transmission electron microscope,X⁃ray diffrac⁃tion,Fourier transform infrared spectroscopy,and X⁃ray photoelectron spectroscopy,and the basic photophysical properties were investigated via UV⁃Vis absorption spectra and fluorescence spectra.Meanwhile,the N,S⁃CDs have excellent luminescence stability with pH,ionic strength,radiation time,and storage time.Experimental results illus⁃trated the present sensor platform exhibited high sensitivity and selectivity in response to baicalein with a detection limit of 85 nmol·L-1.The quenching mechanism is proved to be the inner filter effect.In addition,this sensor can also detect baicalein in biofluids(serum and urine)with good accuracy and reproducibility.

Two Rhodamine-based Turn on Chemosensors with High Sensitivity, Selectivity, and Naked-Eye Detection for Hg^2＋

Two novel rhodamine-based fluorescence enhanced molecular probes （RA1 and RA2） were synthesized, which were both designed as comparative fiuoroionophore and chromophore for the optical detection of Hg^2＋. The recognizing behaviors were investigated both experimentally and computationally. They exhibited high selectivity and sensitivity for Hg^2＋ over other commonly coexistent metal ions in CH3CN/H2O （1：1, V/V） solution. Test shows that hydroxy benzene of rich electron was beneficial to the chelate of Hg^2＋ with sensors. The detection limit was measured to be at least 0.14 p.mol/L. After addition of Hg^2＋, the color changed from colourless to pink, which was easily and hydrogel sensor. detected by the naked eye in both solution

The Recent Advances of Fluorescent Sensors Based on Molecularly Imprinted Fluorescent Nanoparticles for Pharmaceutical Analysis

Fluorescent nanoparticles have good chemical stability and photostability,controllable optical properties and larger stokes shift.In light of their designability and functionability,the fluorescent nanoparticles are widely used as the fluorescent probes for diverse applications.To enhance the sensitivity and selectivity,the combination of the fluorescent nanoparticles with the molecularly imprinted polymer,i.e.molecularly imprinted fluorescent nanoparticles(MIFN),was an effective way.The sensor based on MIFN(the MIFN sensor)could be more compatible with the complex sample matrix,which was especially widely adopted in medical and biological analysis.In this mini-review,the construction method,detective mechanism and types of MIFN sensors are elaborated.The current applications of MIFN sensors in pharmaceutical analysis,including pesticides/herbicide,veterinary drugs/drugs residues and human related proteins,are highlighted based on the literature in the recent three years.Finally,the research prospect and development trend of the MIFN sensor are forecasted.

Ratiometric Fluorescence Detection of 6-Mercaptopurine Based on the Nanohybrid of Fluorescence Carbon Dots and Gold Nanoclusters

The development of a simple and accurate quantitative method for the determination of 6-mercaptopurine (6-MP) is of great importance because of its serious side effects. Ratiometric fluorescence (RF) sensors are not subject to interference from environmental factors, and exhibit enhanced precision and accuracy. Therefore, a novel RF sensor for the selective detection of 6-MP was developed. The present work reports a sensitive and selective RF sensor for the detection of 6-mercaptopurine, by hybridizing carbon nanodots (CDots) and gold nanoclusters (AuNCs) capped with bovine serum albumin (BSA). The CDots serve as the reference signal and the AuNCs as the reporter. On addition of the 6-MP, AuNCs formed aggregates, because the existing cross-links within the AuNCs and BSA structure were broken in favour of the Au-S bonds, which can enhance the fluorescence of AuNCs, while the fluorescence of CDots is stable against 6-MP, leading to distinct ratiometric fluorescence changes when exposed to 6-MP. 6-MP could be detected in the range of 0 - 30.22 μM with a detection limit of 54 nM. The developed sensor was applied for the determination of 6-MP in human serum samples and satisfactory results were obtained.

6-(N,N-Dimethylamino)-2-naphthoylacryl Acid:a Highly Selective and Sensitive Fluorescent Sensor of Copper(Ⅱ)

A novel fluorescent probe,6-（N,N-dimethylamino）-2-naphthoylacryl acid（ACADAN） was designed and synthesized as a fluorescent sensor for Cu^2＋ in aqueous media.Significant amplification of fluorescence signals without causing any discernible change of maximum fluorescence emission wavelength（λ max） was observed upon the addition of Cu^2＋.Importantly,ACADAN is capable of recognizing Cu^2＋ selectively in aqueous media in the presence of various biologically relevant metal ions and the prevalent toxic metal ions in the environment with high sensitivity（detection limit was 0.1 μmol/L）.

A Fiber Optic Sensor for 2-cholrophenol Analysis based on Oxygen Sensing System

A fiber optic 2-cholrophenol（2-CP） sensor was developed based on the fluorescence quenching of molecular oxygen on the oxygen-sensitive membrane and O2 consumption during catalytic oxidation reaction of 2-CP. The 2-CP concentration can be determined by utilizing a lock-in amplifier to measure the change in the fluorescence lifetime of an oxygen-sensitive membrane, in which the tris（2,2′-bipyridyl） ruthenium（II） chloride complexes（Ru（II）（byp）3Cl2） were immobilized in cellulose acetate（CA） via simple hybridized approach. The experimental results show the good linear relationship between the phase delay of sensitive membrane and 2-CP concentration in its detection range of 1×10-7 to 1×10-5 mol/L and 1×10-5 to 1×10-4 mol/L. The detection limit of the sensor is 7×10-8 mol/L（S/N=3） and the response time is 5 min. Our experimental measurements confirmed good response characteristics of the as-prepared fiber optic 2-CP sensor, as well as its capability to detect the 2-CP concentration in practical water samples.