Selective Fluorescence Detection Research Articles

Synthesis and characterization of a unique fused spiro-dihydropyran based chemodosimeter for selective visual and fluorescent detection of Cu2+ ion in aqueous medium by “turn-on” mode

A realistically newly designed Cu2+ ion specific fluorescent chemodosimeter has been synthesized from α,α'-(E,E)-bis(benzylidene)cyclohexanone having a fused spiro-dihydropyran moiety characterized by 2D NMR and X-Ray Crystallographic study. It also demonstrates an irreversible, instant direct visualisation by unaided eye chemosensing property in aqueous buffer (pH 7.4) with a colour change from yellow to orange upto 0.3 × 10−6 M.

Peroxidase-like Activity of Aptamer-Gold Nanoparticles for Selective and Sensitive Fluorescence Detection of Low-Density Lipoproteins

Peroxidase-like Activity of Aptamer-Gold Nanoparticles for Selective and Sensitive Fluorescence Detection of Low-Density Lipoproteins

A "Pincer" Type of Acridine-Triazole Fluorescent Dye for Iodine Detection by Both 'Naked-Eye' Colorimetric and Fluorometric Modes.

Iodine, primarily in the form of iodide (I-), is the bioavailable form for the thyroid in the human body. Both deficiency and excess intake of iodide can lead to serious health issues, such as thyroid disease. Selecting iodide ions among anions has been a significant challenge for decades due to interference from other anions. In this study, we designed and synthesized a new pincer-type acridine-triazole fluorescent probe (probe 1) with an acridine ring as a spacer and a triazole as a linking arm attached to two naphthol groups. This probe can selectively recognize iodide ions in a mixed solvent of THF/H2O (v/v, 9/1), changing its color from colorless to light yellow, making it suitable for highly sensitive and selective colorimetric and fluorescent detection in water systems. We also synthesized another molecular tweezer-type acridine-triazole fluorescent probe (probe 2) that exhibits uniform detection characteristics for iodide ions in the acetonitrile system. Interestingly, compared to probe 2, probe 1 can be detected by the naked eye due to its circulation effect, providing a simple method for iodine detection. The detection limit of probe 1 is determined to be 10-8 mol·L-1 by spectrometric titration and isothermal titration calorimetry measurements. The binding stoichiometry between probe 1 and iodide ions is calculated to be 1:1 by these methods, and the binding constant is 2 × 105 mol·L-1.

Highly efficient photocatalytic removal of antineoplastic drug and selective fluorescence detection of organophosphate pesticide employing NiFe2O4 modified 2D g-C3N4 heterostructures

With the goal to detect, quantify and remove virulent toxins for water decontamination, a dual functional platform based on nickel ferrite (NF) modified magnetically retrievable 2D metal free g-Carbon Nitride (CN), with varied ratios of NF, was fabricated via simple sonication-calcination route. The % degradation of antineoplastic drug, doxorubicin (DXR) were obtained to be 69.8 %, 49.1 %, 71.1 %, 85.4 %, 94.2 %, 88.5 % and 81.7 % for CN, NF, 2-CNNF, 4-CNNF, 6-CNNF, 8-CNNF and 10-CNNF, respectively with corresponding rate constant values of 0.069, 0.047, 0.075, 0.100, 0.148, 0.113 and 0.078 min−1. CNNF heterostructure displayed outstanding photocatalytic performance with 6-CNNF heterostructure displaying highest rate kinetics with rate constant value 2.2 and 3.2 times greater than pure CN and NF, respectively. The charge transfer occurring in CNNF heterostructure followed direct Z-scheme mechanistic pathway, which proffers two advantages of high photoinduced charge carriers separation and optimized redox capacity of binary system. UV–vis DRS, XPS and PL results supported the proposed mechanism. Radical scavenging experiments further validated the role of •O2−, h+ and HO• radicals in degrading target pollutant. Moreover, the fabricated material was efficiently employed as selective and sensitive sensor for fluorescence detection of pesticide, chlorpyrifos (CPF) and DXR with respective LOD values of 4.1 µM in the range of 5 µM to 100 µM and 1.6 µM in the range of 0.1 µM to 40 µM. Real world applicability was established by monitoring CPF and DXR in real water samples. This study presents the designing of multi-functional platform, exhibiting excellent optical as well as physical characteristics, for monitoring and obliteration of noxious pollutants in aqueous environment.

Selective fluoride detection based on modulation of red emissive carbon dots fluorescence by zirconium-alizarin complex: Application to Nile River water and human saliva samples

Fluoride is an essential ion for dental health that is optimally supplemented through drinking water, toothpastes, and other oral hygiene products. This work reports a selective, simple, and inexpensive fluorescent sesnor for fluoride quantification. The sensor exploits the red fluorescence of carbon dots coupled with the colorimetric response of a zirconium-alizarin complex. The zirconium-alizarin exhibits an absorption band at 530 nm that overlaps the carbon dot excitation peak, resulting in inner filter effect-based quenching of the 612 nm red emission. However, in the presence of fluoride, binding disrupts the zirconium complex, releasing free alizarin with an absorption blue shifted to 420 nm. This reduces spectral overlap and restores carbon dot fluorescence. The carbon dots were synthesized by a hydrothermal method and exhibited excellent fluorescence quantum yield (16.3 %). Structural and optical characterizations were performed using TEM, XRD, XPS, FTIR, UV–vis, and fluorescence techniques. Under optimized conditions, the probe provided selective turn-on fluorescence detection of fluoride with a linear response from 1.0 to 130.0 μM and limit of detection (S/N = 3) of 0.32 μM. Practical utility was demonstrated by accurate quantification of fluoride in Nile River water and human saliva samples. This dual nanoprobe strategy offers a rapid and cost-effective platform for fluoride analysis in support of healthcare and environmental monitoring applications.

Chemical surface modification of carbon dots with Germanium: A highly sensitive and selective ratiometric fluorescence probe for Mg2+ detection using DFT and TD-DFT

In this study, we chemically modified carbon dots (Cdots) using germanium, enhancing their sensitivity and selectivity as a ratiometric fluorescence probe for precise detection of Mg2+ ions. Excitation of the modified Cdots resulted in a distinct emission peak at 527 nm, enabling accurate measurement of Mg2+ concentrations across a linear range. The surface modification with germanium led to the creation of novel emitting centers on the Cdots' surface. Theoretical calculations using density functional theory (DFT) revealed the effective suppression of these emitting centers through a photo-induced electron transfer (PET) process, utilizing the nitrogen lone pair electrons on the Cdots' surface. Furthermore, adjacent Cdots' surface pyrazino[2,3-f][1,10]-phenanthroline (PPT) nitrogen atoms formed chemical bonds with Mg2+ ions, resulting in the formation of aggregated Cdots. Consequently, the intricate complexation terminated the PET process, resulting in a novel emission peak at longer wavelengths. This study presents a highly sensitive and selective ratiometric fluorescent detection system with exceptional low concentration detection limit for precise Mg2+ ion detection.

In situ generated dimethylamine constructs a robust hydrogen-bonded organic framework for selective fluorescence detection

The in situ generated DMA molecules constructs a robust and fluorescent hydrogen-bonded organic framework with DBP.

Carbon dots-cadmium sulfide quantum dots nanocomposite for 'on-off' fluorescence sensing of chromium(vi) ions.

This work involves fluorescent probe which is composed of carbon dots (CD) and cadmium sulfide quantum dots (CdS QD) for the sensitive and selective fluorescence detection of chromium(vi) ions. The blue fluorescent carbon dots were synthesized by hydrothermal method from natural precursor apricot. The carbon dots-cadmium sulfide quantum dots (CD-CdS QD) nanocomposite was synthesized and all as-synthesized products were characterized using different characterization techniques. It showed white fluorescence under UV light which was quenched selectively in the presence of chromium(vi) ions due to the inner filter effect (IFE). The linear decrease in the white fluorescence was observed in the concentration range 2-120 μM of chromium(vi) ions with the limit of detection 2.07 μM. This is novel probe for the sensitive, selective and rapid detection of chromium(vi) ions.

A thiophene-linked terpyridine based phenanthridine chemoreceptor for Cd2+ and Cr3+ selective ratiometric fluorescence detection in environmental water and rice samples

BackgroundThe studied materials, Cadmium (Cd2+) and Chromium (Cr3+) are highly toxic, and it focuses on investigating various environmental sources, such as industrial processes and waste water. When quantities of Cr3+ and Cd2+ exceed the allowable limit, biological toxicity and hazardous environmental pollution are unavoidable. In order to address this problem, we introduce 5-(5-(4-([2,2':6′,2″-terpyridin]-4′-yl) phenyl) thiophen-2-yl)-7,8,13,14-tetrahydrodibenzo [a,i] phenanthridine (TPTP), a dual-emission response chemosensor that employs a colorimetric and fluorescence turn-on approach for the rapid, sensitive, and discriminate detection of Cr3+ and Cd2+ ions. ResultsWe created a newly designed luminous TPTP sensor based on intramolecular charge transfer (ICT). TPTP sensor probe specifically determined Cr3+ and Cd2+ ions with an immediate colour shift from cyan to green and orange in CH3CN: H2O (6:4) solvent solution. The permissible level set by the Environmental Protection Agency (EPA) of the United States for the presence of Cr3+ and Cd2+ ions in drinking water was higher than the detection level of 3.5 and 9.7 nM, by this sensor respectively. NMR titrations, HRMS, and theoretical calculation methods were employed to examine the accurate sensing processes of TPTP and complexes. SignificanceThis is an effective method of detecting Cr3+ and Cd2+ ions in an environmental system using a ratiometric methodology. In addition, TPTP was used to determine the concentration of Cr3+ and Cd2+ ions in natural water and food samples. Fluorescent bio-imaging studies revealed that the present sensor TPTP could identify Cr3+ and Cd2+ ions inside living HeLa cells. A paper kit analysis has been done on TPTP, which has a time-to-result of less than 1 s and offers a cost-effective assay. As a result, the platform offers portability.

Molecularly imprinted alginate-PVP membrane for the selective fluorescence detection of flavonoids in foods: A practical case for rutin

Flavonoids benefits have rendered them interesting molecules in the realm of sensing. However, a significant challenge lies in their selective and sensitive detection in complex matrices. One of the most relevant flavonoids is rutin (RU), a flavonoid glycoside. In this work, a novel, straightforward, and green approach is proposed to prepare a selective molecularly imprinted membrane (MIM) for RU based on sodium alginate and polyvinylpyrrolidone, following a central composite design for the optimization of the MIM preparation. The developed membrane was characterized by Fourier transform infrared spectroscopy, thermo-gravimetric analysis, and scanning electron microscopy to assess the functional, thermal, and morphological properties of the membrane, respectively. The developed MIM was successfully applied for the selective and sensitive solid spectro-fluorescence sensing of RU within a concentration range of 0.01–10 µg/mL and a limit of detection (LOD) of 3.6 ng/mL. Furthermore, a new 3D-printed smartphone accessory was designed and applied in smartphone-based solid fluorescence assays. This innovation enabled portable, label-free, rapid, cheap, and green detection of RU across a concentration interval of 0.05–10 µg/mL, with a LOD of 20 ng/mL. Moreover, MIM showed important long-term stability and good reusability (10 regeneration cycles). Finally, the proposed methodology was validated using an accuracy statistical approach. Overall, this study didn’t only demonstrate an innovative and straightforward approach to imprinting technology but also highlighted the promise of the proposed smartphone-based sensing method as a versatile tool with a broad range of applications to automatize the analysis and to enhance portable diagnosis technology.

Solvent-free mechanochemical synthesis of a sodium disulfonate covalent organic framework for simultaneous highly efficient selective capture and sensitive fluorescence detection of fluoroquinolones

Covalent organic frameworks (COFs) have great adsorption potential due to their tunable pore size and pore architecture as well as tailorable functionalities. However, the green and rapid synthesis of COFs with excellent adsorption properties remains a great challenge. Here, we presented a solvent-free and facile mechanochemical approach for the synthesis of COFs. The as-prepared COF TpBD-(SO3Na)2 containing sulfonate ions exhibited good thermal and chemical stability and can serve as an effective adsorbent for selective capture of fluoroquinolone antibiotics (FQs) benefiting from the ionic interface and abundant negatively charged sites. The maximum adsorption capacities of norfloxacin, enoxacin, and ciprofloxacin were 1709.6, 1661.5, and 1362.8 mg g−1, respectively, which outperformed those of other reported adsorbents. The adsorption mechanism was deeply explored through characterizations combined with density functional theory calculations, proving the synergistic adsorption effects of TpBD-(SO3Na)2 and FQs, including π-π* interactions, electrostatic interactions, and hydrogen bonding. Moreover, a fluorescence detection platform for FQs was developed based on the fluorescence signal of sodium disulfonate TpBD-(SO3Na)2. The limit of detection of norfloxacin was 8 nmol/L with a linear range from 0.03 to 6 μmol/L. This research provides a new strategy for the green synthesis of COFs and expands their application in the synchronous detection and removal of FQs in aquatic environments.

1D + 3D → 3D zinc polyrotaxane MOF: Selective fluorescent detection of nitrobenzene, uric acid and sucrose and photocatalytic degradation of Rose Bengal and Congo Red dyes

A new Zn based polyrotaxane 3D metal-organic framework (MOF), {[Zn3(BTC)2(Bimb)3.5][Zn(HCOO)(Bimb)1.5]·CH3COO·2(CH3)2NH·2DMF·9H2O}n (KA@MOF-S2)(Bimb = 1,4-bis[(1H-imidazol-1-yl)methyl]benzene, BTC3‒ = 1,3,5-benzenzetricarboxylate) has been synthesized under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that KA@MOF-S2 exhibits a novel 1D + 3D → 3D interpenetratedPolyrotaxane MOF architecture. KA@MOF-S2 possesses a new 3,3,3-c net 3-nodal interpenetrated network with (122.14)(8.122)(83)2 topology. KA@MOF-S2 can be used as a selective fluorescence sensing material for the quantitative detection of VOCs (Acetone, NB), antibiotic (NFT) and biomolecules (UA, sucrose) and photocatalytic degradation of Rose Bengal (RB) and Congo Red (CR) dye under sun-light irradiation.

Facile preparation of tetraphenylethylene-based porous polymer with dual role of adsorption and detection for trinitrotoluene

A novel porous polymer, denoted as tetraphenylethene-based porous polymer (PTPEK), was synthesized via a catalyst-free C–O coupling reaction. The unique combination of dipole-π interactions and π-π interactions within PTPEK facilitated exceptional adsorption property towards trinitrotoluene (TNT). Furthermore, the incorporation of tetraphenylethene groups, which exhibit aggregation-induced emission (AIE) activity, endowed PTPEK with remarkable TNT detection capability. Simultaneously, PTPEK showed excellent selective adsorption capability and outstanding selective fluorescence detection performance for TNT. At room temperature (298 K), PTPEK demonstrated a maximum TNT adsorption capacity of 209.2 mg g−1, reaching 65 % of its adsorption equilibrium within just 1 h. Additionally, PTPEK exhibited a rapid quenching time of 125 s for TNT, with a low detection limit of 4.56 × 10−6 mol/L. Notably, PTPEK also displayed excellent recyclability characteristics.

A lanthanide metal-organic framework for highly selective and sensitive fluorescence detection of ciprofloxacin

The exploration of an efficient and sensitive method for the detection of ciprofloxacin (CIP) is important for the protection of human health and the ecological environment. In this study, a water-stable lanthanide metal-organic framework ratiometric fluorescence sensor (Dy-MOF) was prepared for the detection of ciprofloxacin. This versatile Dy-MOF can easily distinguish various antibiotics and displays a self-calibrated fluorescence response to ciprofloxacin (CIP). Under the ratiometric two-dimensional decoding map, a unique combination is formed using the ratio of the emission peak of the ligand to the occurrence peak of Dy3+, which makes it possible to distinguish the various antibiotics. The sensor exhibited good selectivity, sensitivity and recoverability for CIP with a detection limit of 0.27 µM. In addition, the fluorescent sensor was used to detect CIP in pure milk samples with a recovery of (97.5–107.5 %). In order to investigate the sensing mechanism of CIP, we discussed the energy transfer process between Dy-MOF and CIP in detail. This work provides a promising strategy for the development of simple and effective ratio sensors.

Highly sensitive and selective ratiometric fluorescent and visual detection of Cu2+ based on the hydroxytyrosol–naphthoresorcin–quantum dots sensing platform

Fluorescence-based visual analysis has attracted considerable attention in on-site detection owing to their distinct color gradient changes, easy operation and high sensitivity. In this work, we construct an exceptionally simple dual-emission ratio fluorescence sensor through the synergy of hydroxytyrosol (HYT), naphthoresorcin (NR) and ZnCdSe/ZnS quantum dots (QDs), namely HYT–NR–QD, for the fluorescent and visual detection of Cu2+. The design of ratiometric nanosensor is based on our new finding that Cu2+ can catalyze the reaction between HYT and NR to produce a cyan-emitting fluorophore (emission: 480 nm), and the copper species existed in the form of Cu+ and Cu2+ in reaction system. After adding QDs (emission: 605 nm), the free Cu+, Cu2+ and the resulting fluorophore in this system caused a great reduction in the FL intensity of QDs, due to the rapid cation exchange reaction between QDs and Cu2+/Cu+ as well as the inner filter effect between QDs and the resulting fluorophore. Overall, Cu2+ induced emission intensity changes at 480 and 605 nm leads to a distinct color change from red to cyan. A ratiometric fluorescence Cu2+ sensor with a lowest concentration of 3.42 nM was developed. Furthermore, the concentration of Cu2+ can be conveniently reflected with a smartphone application by identifying the RGB value. Moreover, the method proposed by us can be explored for Cu2+ determination in environmental water samples with a satisfying result, providing a novel, simple-operating and on-site detection of Cu2+ in water samples.

Bacteriophage-Conjugated Fluorescent Nanoemulsion as a Novel Optical Probe for Highly Selective Bacterial Detection

Abstract Infectious disease mortality has decreased due to effective drugs and healthcare. However, global health remains threatened by infectious diseases. New methods of rapid and accurate bacterial detection have attracted considerable attention. Fluorescence detection of whole bacterial cells offers high sensitivity, quantitative analysis, and simple operation. A highly fluorescent bioconjugated probe improves sensitivity and selectivity. This study presents a novel, bright fluorescent probe comprising a bacteriophage and a fluorescent nanoemulsion (fNE) as biorecognition and signal transduction elements, respectively. We demonstrate that fluorescence microscopy imaging using the S. aureus-specific phage, S13′-fNE (phage-fNE), detects S. aureus in the presence of E. coli or S. pseudintermedius, another closely related Staphylococci, in a highly selective manner. Furthermore, fNEs with high dye loadings exhibit considerably greater brightness compared to the fluorescent dye alone, making them suitable for sensitive fluorescence imaging. Phage-fNEs can quantitatively detect S. aureus at 104–108 colony-forming units per milliliter (CFU mL−1), with a limit of detection of 8 × 104 CFU mL−1. This result is comparable to the lowest value achieved by microscopic bacterial detection, with no preconcentration or enzymatic signal enhancement methods used. Bioconjugated fNEs open new avenues for highly selective and sensitive fluorescent detection of bacteria.

Amorphous amEu-NH2BDC and amTb-NH2BDC as ratio fluorescence probes for smartphone-integrated naked eye detection of bacillus anthracis biomarker

The abnormal concentration of anthrax spore biomarker 2,6-pyridinedicarboxylic acid (2,6-DPA) will seriously affect public health. Therefore, a sensitive and rapid assay for 2,6-DPA monitoring is of vital importance. In this work, novel nano-sized amorphous Eu-NH2BDC (amEu-NH2BDC) and amorphous Tb-NH2BDC (amTb-NH2BDC) metal organic frameworks are prepared by adjusting the ratio of metal and ligand, respectively. Both of them exhibit highly sensitive and selective ratiometric fluorescence detection for 2,6-DPA with wider linear range and lower detection limit in aqueous solutions and human serum. Attributed to the coordination effect of 2,6-DPA in triggering the characteristic fluorescence emissions of Eu3+or Tb3+ by replacing coordinated solvent molecules, as evidenced by ultraviolet–visible spectroscopy, the fluorescence lifetimes analysis, thermal gravimetric analysis, Fourier-transform infrared spectroscopy, density functional theory (DFT) simulations and X-ray photoelectron spectroscopy. In addition, the amEu-NH2BDC or amTb-NH2BDC loaded paper-based microsensors are constructed for real-time and sensitive detection of 2,6-DPA and coupled with a smartphone-assisted visual portable device.

An "on-off-on" fluorescent switch based on luminous covalent organic framework for the rapid and selective detection of glyphosate.

Glyphosate, the most used herbicide in the world, has a residue problem that cannot be ignored. However, glyphosate itself does not have fluorescence emission and lacks the conditions for fluorescence detection. In this work, a rapid and selective fluorescence detection method of glyphosate was designed by an "on-off-on" fluorescent switch based on luminous covalent organic framework (L-COF). Only the fixed concentration of Fe3+ as intermediate could trigger the fluorescent switch and no incubation step was required. The proposed method showed good accuracy with correlation coefficient of 0.9978. The method's limits of detection and quantitation were 0.88 and 2.93 μmol/L, which were lower than the maximum allowable residue limits in some regulations. Environmental water samples and tomatoes were selected as actual samples to verify the application in complex matrix. A satisfactory mean recovery from 87% to 106% was gained. Furthermore, Fe3+ could induce fluorescence quenching of L-COF through photo-induced electron transfer (PET) effect, while the addition of glyphosate could block PET effect to achieve the detection. These results demonstrated the proposed method had abilities to detect glyphosate, and broadened the application of L-COF.

A molecularly imprinted photopolymer based on mesh TpPa-2 embedded with perovskite CsPbBr3 quantum dots for the sensitive solid fluorescence sensing of patulin in apple products.

Here, a novel molecularly imprinted photopolymer was prepared using CsPbBr3 quantum dots as the fluorescence source, TpPa-2 as substrate for selective solid fluorescence detection of patulin (PAT). TpPa-2 can promote efficient recognition of PAT due to its unique structure and significantly improve the fluorescence stability and sensitivity. The test results showed that the photopolymer exhibited large adsorption capacity (131.75mg/g), fast adsorption ability (12 mins), superior reusability and high selectivity. The sensor proposed had good linearity for PAT in the range of 0.2-20ng/mL and was applied to the analysis of PAT in apple juice and apple jam with a limit of detection as low as 0.027ng/mL. Therefore it maybe a promising method for solid fluorescence detection of trace PAT in food analysis.

Fast, Selective and Sensitive Fluorescence Detection of Levofloxacin, Fe3+ and Cu2+ Ions in 100% Aqueous Solution Via Their Reciprocal Recognition.

The fluorescence detection of ions and pharmaceutical effluents by using organic chemosensors is a valuable surrogate to the currently existing expensive analytical methods. In this regard, the design of multi-functional chemosensors to recognize desirable guests is of utmost importance. In this study, we first show that levofloxacin (LVO) is able to use as a fluorescent chemosensor for the detection of biologically important Cu2+ (turn-off) and Fe3+ (turn-on) ions via independent signal outputs in 100% aqueous buffer solutions. Next, using the reciprocal recognition of LVO and Fe3+ provides a unique emission pattern for the detection of LVO. This approach exhibited a high specificity to LVO among various pharmaceutical samples, namely acetaminophen (AC), azithromycin (AZ), gemifloxacin (GEM) and ciprofloxacin (CIP) and also showed great anti-interference property in urine. The attractive features of this sensing system are availability, easy-to-use, high sensitivity (limit of detection = 18 nM for Cu2+, 22 nM for Fe3+ and 0.12 nM for LVO), rapid response (5 s) with an excellent selectivity.