Pronounced Fluorescence Response Research Articles

Unlocking multi-mode sensing potential: Phosphorus-doped graphitic carbon nitride quantum dots for Ag+, ciprofloxacin, and riboflavin analysis in environment and food matrices

The simultaneous detection of multiple analytes through a single fluorescence sensor is highly attractive. In this study, phosphorus-doped graphitic carbon nitride quantum dots (P-CNQDs) were developed, achieving multi-mode sensing through three distinct response mechanisms. The preparation involved using melamine as the carbon and nitrogen source and ammonium dihydrogen phosphate as the phosphorus source. Uniform and narrowly distributed P-CNQDs were successfully synthesized through chemical oxidation and hydrothermal methods, with an average size of 2.4 nm. These unique P-CNQDs exhibited fluorescence quenching through photo-induced electron transfer (PET) in response to Ag+. Additionally, the formation of hydrogen bonds and coordination interactions between P-CNQDs-Ag+ and ciprofloxacin (CIP) led to a pronounced fluorescence response to CIP by the chelation enhanced fluorescence (CHEF) mechanism. Furthermore, leveraging the principle of fluorescence resonance energy transfer (FRET), P-CNQDs-CIP served as a ratio fluorescence sensor for riboflavin (RF), enabling ultra-sensitive detection of RF. The combination of PET, CHEF, and FRET response mechanisms successfully facilitated multi-mode sensing for Ag+, CIP, and RF. The detection ranges were 0.05–100 μM, 0.002–2 μM, and 0.05–60 μM, with corresponding lowest detection limits of 17.1 nM, 1.1 nM, and 29.2 nM, respectively. This versatile sensor has been effectively applied to real samples, including the detection of river water and vitamin B2 tablets.

An acid-base resistant Zn-based metal-organic framework as a luminescent sensor for mercury(II)

A monocyclic organic ligand 5-aminoisophthalic acid (H2APA) with one amino and two carboxylic groups, has been employed to construct a stable Zn-based metal-organic framework, ZnAPA. It features a 3D supramolecular network containing the pores with a size of 8.2 ​Å and uncoordinated carboxylic oxygen atoms, exhibiting a pronounced fluorescence response (fast response, high sensitivity and selectivity) to Hg2+ ion over other metal ions in aqueous solution. The possible fluorescence-based sensing mechanism is also involved. Importantly, ZnAPA shows extraordinary acid-base resistant stability, highlighting its potential use for detection of Hg2+ in practical applications.

Peptide-Based Probes with an Artificial Anion-Binding Motif for Direct Fluorescence "Switch-On" Detection of Nucleic Acid in Cells.

This work reports two new peptide-based fluorescence probes (1 and 2) for the detection of ds-DNA at physiological pH. Probes 1 and 2 contain a fluorophore, either amino-naphthalimide or diethyl-aminocoumarin, respectively, and two identical peptide arms each equipped with a guanidiniocarbonylpyrrole (GCP) anion-binding motif. These probes show "switch-on" fluorescence response upon binding to ds-DNA, whereby they can differentiate between various types of polynucleotides. For instance, they exhibit more pronounced fluorescence response for AT-rich polynucleotides than GC-rich polynucleotides, and both give only negligible response to ds-RNA. The fluorimetric response of 1 is proportional to the AT-basepair content in DNA, whereas the fluorescence of 2 is sensitive to the secondary structure of the polynucleotide. Fluorescence experiments, thermal melting experiments and circular dichroism studies suggest that 1 interacts with ds-DNA in a combined intercalation and minor groove binding, whereas 2 interacts mainly with the outer surface of DNA/RNA. As 1 and 2 have a very low cytotoxicity, 1 can be applied for the imaging of nuclear DNA in cells.

Highly sensitive and selective detection of mercury (II) based on a zirconium metal-organic framework in aqueous media

A novel metal-organic framework (MOF) fluorescent probe UiO-66-PSM is obtained by the copper-catalyzed azide-alkyne click (CuAAC) reaction of UiO-66-N3 with phenylacetylene. The click-generated triazole unit can act as the metal binding site to coordinate with Hg2+, which exhibits the most pronounced fluorescence response (rapid response, excellent selectivity, and high sensitivity) over other metal ions. Moreover, it is capable of detecting Hg2+ in environmental water samples without any structural disintegration of the framework, indicating its high potential in practical applications.

Preparation of good solubility poly(triazole)s for Hg2+ detection via click chemistry

Polymers used as fluorescence sensors have been gained increased attention due to their high sensitivity originating from the sensory signal amplification. In this paper, the polymer incorporating triazole moieties was prepared via click reaction and used as fluorescence sensor for transition metal ions detection. The structures and properties of the polymer were characterised and evaluated with FTIR, NMR, FL, and DLLS analyses. The triazole polymer exhibited good solubility and high molecular weight. Compared with other metal ions, such as Mg2+, Cu2+, Pb2+, Sr2+, Ca2+, Al3+, Zn2+, Bi2+, Ba2+ and Fe3+, Hg2+ can exhibit the most pronounced fluorescence response of the polymer using triazole moiety as the metal recognition group. The results indicate this kind of polymer with triazole moiety based on click reaction can be used as a selective fluorescence sensor for Hg2+detection.

A highly selective ratiometric fluorescent chemosensor for Zn2+ ion based on a polyimine macrocycle

A new ratiometric fluorescent chemosensor based on a polyimine macrocycle ligand 1 has been synthesized. The chemosensor can exhibit a pronounced fluorescence response and high selectivity to Zn2+ ion over other 15 metal ions, including Cd2+. Sensor 1 appears an emission peak at 370 nm. Upon the addition of Zn2+ ion, the typical emission peak for 1 at 370 nm is obviously quenched, but a new emission peak at around 470 nm appears and shows a large enhancement due to the formation of a 1:1 Zn2+-1 complex. In addition, there is a good linear relationship between the fluorescence ratio I470nm/I370nm and the concentration of Zn2+, which makes a ratiometric assay of Zn2+ ion possible.

Protein binding to soft polymeric layers: a quantitative study by fluorescence spectroscopy

We present a comprehensive investigation of the adsorption of several proteins, i.e., lysozyme, β-D-glucosidase, and cytochrome c, onto microgels in aqueous solution. The microgels consist of a solid core from polystyrene (PS) onto which a shell of poly(N-isopropylacrylamide) (pNiPAm) together with 10 mol% acrylic acid is grafted. The pronounced fluorescence response observed upon transfer of fluorescent marked lysozyme from the bulk solution to the gel allows us to monitor its uptake by the shell in situ. All data demonstrate directly that full equilibrium is reached rendering the binding of proteins to the particles as a reversible process. We also study the competitive adsorption of lysozyme with cytochrome c or β-D-glucosidase. Here we show that the data obtained for a mixture of lysozyme and cytochrome c can be modeled quantitatively by a competitive Langmuir isotherm. Using time-resolved fluorescence spectroscopy we elucidate the kinetics of protein adsorption. We find that the uptake of proteins by these particles is described by a fast, diffusion-limited binding regime which is followed by a slow binding regime, most probably caused by a slow rearrangement of the proteins within the network. All data demonstrate that charged pNiPAm-microgels present a model system for which the thermodynamics and kinetics of protein adsorption including competitive adsorption can be analyzed in a quantitative manner.

Hg 2+ detection by aniline-based conjugated copolymers with high selectivity

Conjugated polymers ( P1, P1L and P2– P5) constructed by alkynyl-substituted aniline and substituted arene analogs could be synthesized through Pd-catalyzed Sonogashira coupling. The responsive optical properties of poly(2-ethynyl aniline) ( P1 and P1L for different molecular weights, P1L with longer chains on average) toward various metal ions (including Ni 2+, Ag +, Cu 2+, Zn 2+, Fe 3+, Fe 2+, Mn 2+, Na +, Ca 2+, Pb 2+, K +, Cr 3+, Al 3+, Cd 2+, Pt 2+, Au 3+ and Tl 3+) were investigated. Hg 2+ exhibited the most pronounced fluorescence response of both P1 and P1L without interference from those coexistent ions due to aniline in the polymer backbone as the metal binding ligand, while other metal ions does not cause obvious change of fluorescence. Compared with P1, P1L exhibits better sensitivity toward Hg 2+. Introducing pyridyl, thienyl or phenyl groups into the polymer backbone would weaken the quenching responses to Hg 2+ compared with P1. The results indicated P1 and P1L could be used as a selective fluorescence sensor toward Hg 2+.

Fluorescence Polymer Incorporating Triazole and Benzo[2,1,3]thiadiazole Moieties for Ni²+ Detection

Conjugated polymer could be obtained by the polymerization of 4,7-diethynylbenzo[2,1,3]thiadiazole (M-1) with 1,4-diazidobenzene (M-2) via click reaction. The polymer shows strong blue-green fluorescence due to the extended π-electronic structure in the main chain backbone. The responsive optical properties of the polymer on various transition metal ions were investigated by fluorescence spectroscopy. Compared with other transition metal cations, such as Co²+, Hg²+, Ag+, Cd²+, Cu²+ and Zn²+, Ni²+ showed the most pronounced fluorescence response in the presence of the conjugated polymer. The results indicate this kind of polymer with benzo[2,1,3]thiadiazole and triazole units can be used as a selective fluorescence sensor for Ni²+ detection.

Polymer-based fluorescence sensor incorporating triazole moieties for Hg2+ detection via click reaction

The polymer could be obtained by the polymerization of 1,4-dibutoxy-2,5-diethynylbenzene (M-1) with 1,4-diazidobenzene (M-2)via click reaction. The polymer show blue fluorescence. The responsive optical properties of the polymer on various transition metal ions were investigated by fluorescence spectra. Compared with other cations, such as Co2+, Ni2+, Ag+, Cd2+, Cu2+ and Zn2+, Hg2+ can exhibit the most pronounced fluorescence response of the polymer Hg2+ can exhibit the most pronounced fluorescence response of the polymer due to triazole moiety in the polymer main chain as the metal binding ligand. The results indicate this kind of conjugated polymer with triazole moiety synthesized by click reaction can be used as a selective fluorescence sensor for Hg2+ detection.

Polymer‐based fluorescence sensors incorporating chiral binaphthyl and benzo[2,1,3]thiadiazole moieties for Hg2+ detection

AbstractThree chiral polymers P‐1, P‐2, and P‐3 could be obtained by the polymerization of (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2, 2′‐binaphthol (R‐M‐1), (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2,2′‐bisoctoxy‐1,1′‐binaphthyl (R‐M‐2), and (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2,2′‐bis (diethylaminoethoxy)‐1,1′‐binaphthyl (R‐M‐3) with 4,7‐diethynyl‐benzo[2,1,3]‐thiadiazole (M‐1) via Pd‐catalyzed Sonogashira reaction, respectively. P‐1, P‐2, and P‐3 can show pale red, blue–green, and orange fluorescence. The responsive optical properties of these polymers on various metal ions were investigated by fluorescence spectra. Compared with other cations, such as Co2+, Ni2+, Ag+, Cd2+, Cu2+, and Zn2+, Hg2+ can exhibit the most pronounced fluorescence response of these polymers. P‐1 and P‐2 show obvious fluorescence quenching effect upon addition of Hg2+, on the contrary, P‐3 shows fluorescence enhancement. Three polymer‐based fluorescent sensors also show excellent fluorescence response for Hg2+ detection without interference from other metal ions. The results indicate that these kinds of tunable chiral polybinaphthyls can be used as fluorescence sensors for Hg2+ detection. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 997–1006, 2010

A highly selective and sensitive fluorescence chemosensor based on optically active polybinaphthyls for Hg 2+

The chiral polymer was synthesized by the polymerization of 4,7-diethynylbenzo[2,1,3]-thiadiazole ( M- 1) with ( R)-6,6′-dibutyl-3,3′-diiodo-2,2′-bis(diethylaminoethoxy)-1,1′-binaphthyl ( R - M- 1) via Pd-catalyzed Sonogashira reaction. The chiral polymer has orange fluorescence due to the extended π-electronic structure between binaphthyl unit and benzo[2,1,3]thiadiazole ( BT) group via ethynyl bridge. The responsive optical properties of the polymer on various metal ions were investigated by fluorescence spectra. The fluorescence of the chiral polymer can produce the pronounced enhancement as high as 1.8-fold upon addition of 1:2 molar ratio of Hg 2+. Compared with other cations, such as K +, Mg 2+, Pb 2+, Co 2+, Ni 2+, Ag +, Cd 2+, Cu 2+, Zn 2+, Mn 2+ and Fe 3+, Hg 2+ can produce the pronounced fluorescence response of the polymer. The result indicates this kind of chiral polybinaphthyls incorporating diethylamino and benzo[2,1,3]thiadiazole ( BT) moieties as receptors exhibits highly sensitive and selective behavior for Hg 2+ detection.

Acid/Base‐Sensitive Ring‐Opening Metathesis Polymers Based on Phenanthroimidazole Dyes

AbstractPoly(norbornenes) with pendant 2‐phenyl‐1H‐phenanthro[9,10‐d]imidazole in different ratios were prepared and their photophysical properties were studied in the presence and absence of acids. The polymers exhibited good film‐forming properties, which paved the way to study their acid/base‐sensitivity in the solid state. Polymer films with a high fluorophore content exhibited self‐absorption in their non‐protonated form and a pronounced fluorescence response in the presence of gaseous HCl. In contrast, thin films of the polymer with a low dye content showed almost no self‐absorption and only a poor response to the acidic analyte.magnified image