A multifunctional upconversion nanoparticles probe for Cu2+ sensing and pattern recognition of biothiols

Lanthanide-doped upconversion nanoparticles (Ln-UCNPs) are a new type of nanomaterials with excellent fluorescence properties, which are well applied in fluorescent biosensing. Herein we developed a multifunctional probe based on the surface engineering of core-shell structure UCNPs with polyacrylic acid (PAA). The developed PAA/UCNPs probe could be highly selective to detect and respond to Cu²⁺ at different pH. Cu²⁺ could easily combine with the carboxylate anion of PAA to quench the fluorescence of UCNPs. Therefore, we creatively proposed a fluorescent array sensor (PAA/UCNPs-Cu²⁺), in which the same material acted as the sensing element by coupled with pH regulation for pattern recognition of 5 thiols. It could also easily identify the chiral enantiomer of cystine (l-Cys-and d-Cys), and distinguish their mixed samples with different concentrations, and more importantly, it could be combined with urine samples to detect actual level of homocysteine (Hcys) to provide a new solution for judging whether the human body suffers from homocystinuria.     

Synthesis and optical characterization of novel enantiopure BODIPY linked azacrown ethers as potential fluorescent chemosensors

Two novel enantiopure BODIPY linked azacrown ether chemosensors were prepared by reacting 3-chloro-5-methoxyBODIPY with new enantiopure monoaza-18-crown-6 ether ligands bearing two methyl and isobutyl groups on their chiral centres, respectively. The latter compounds were synthesized starting from optically active tetraethylene glycols in six steps. The operation of chemosensors is based on the intramolecular charge transfer (ICT) process. They exhibit pronounced off-on type fluorescent responses to some metal ions and chiral primary aralkyl ammonium ions, in particular to Ca²⁺ and Pb²⁺. Even in the case of 1:1 ratio of Ca²⁺ and Pb²⁺ ions to the ionophores, the fluorescence intensities and quantum yield values increased more than 10-fold, as well as both the absorption and emission bands were blue-shifted by about 20-30 nm (hipsochromic effect) in acetonitrile. The formation of relatively stable complexes allowed the determination of log K_s values by the mole-ratio method.     

Synthesis and fluorescent properties of novel chiral 1,2-diaminocyclohexane substituted ligands and their complexes

A series of novel chiral 1,2-diaminocyclohexane derivatives bearing heterocyclic units were synthesized via improved methods under ultrasonic irradiation. The photophysical properties of compounds were studied in ethanol, methanol, and chloroform. The sensitivity of these amines toward Cu²⁺, Cd²⁺, and Ni²⁺ was studied by the UV–vis and fluorescent methods. The π-electron structure of thiophene and bithiophene containing sensors is the most active toward all above mentioned metal ions and is highly selective for Ni²⁺ and Cd²⁺.     

Fluorescence turn-on chemodosimeter for rapid detection of mercury (II) ions in aqueous solution and blood from mice with toxicosis

The heavy metal mercury (Hg) is a threat to the health of people and wildlife in many environments. Among various chemical forms, Hg²⁺ salts are usually more toxic than their counterparts because of their greater solubility in water; thus, they are more readily absorbed from the gastrointestinal tract into circulation. Therefore, new chemical receptors for detecting Hg²⁺ ions in circulation are needed. In this study, we developed a rhodamine-based turn-on fluorescence probe to monitor Hg²⁺ in aqueous solution and in blood of mice with toxicosis. The chemodosimeter responds to Hg²⁺ ions stoichiometrically, rapidly, and irreversibly at room temperature as a result of a chemical reaction that produces strongly fluorescent oxadiazole. The new fluorescent probe shows good fluorescence response, with high sensitivity and selectivity, toward Hg²⁺ ions in aqueous solution and in blood from mice with toxicosis and facilitates the naked-eye detection of Hg²⁺ ions.     

A New Fluorescent Chemosensor for Metal Ions Based upon 1,8‐Naphthalimide and 8‐Hydroxyquinoline

A new fluorescent chemosensor based upon 1,8‐naphthalimide and 8‐hydroxyquinoline was synthesized, and its fluorescent properties in the presence of different metal cations (Hg²⁺, Ag⁺, Zn²⁺, Fe²⁺, Cd²⁺, Pb²⁺, Ca²⁺, Cu²⁺, Mg²⁺, and Ba²⁺) were investigated. It displayed fluorescence quenching with some heavy and transition metal (HTM) ions, and the quenching strongly depended on the nature of HTM ions.     

新型席夫碱配体及其Mn3+、Fe3+、Ni2+、Cu2+配合物的合成与表征

0引言手性环氧化物是合成许多天然产物、光学活性材料、光学活性药物等的重要中间体[1]。上世纪60年代以来,手性过渡金属配合物作为烯烃不对称环氧化的催化剂越来越受到人们的重视[2]。研究表明,某些席夫碱金属配合物具有仿酶催化活性,在仿酶催化剂的合成及应用方面占有重要地位[3]。目前,人们将水杨醛衍生物与光学活性胺的席夫碱金属配合物用于不对称环氧化、不对称环丙烷化等反应,具有很高的对映体选择性[4]。同时发现配体的电子效应直接影响配合物的催化活性和对映体选择性。为进一步研究配体的电子性能对配合物催化性能的影响,我们设计…     

Phenanthroline-based fluorescence sensors for Eu3+ ion and subsequent enantioselective discriminating of malate

A pair of novel chiral fluorescent and colorimetric sensors L1 and D1 had been designed and synthesized, which were based on phenanthroline as the fluorophore and mandelohydrazide as the binding site. They showed selective recognition toward Eu³⁺ ion as ‘turn-off’ mode in DMSO-H₂O solution (v/v = 1:5, 10 mM HEPES, pH = 7.4). The fluorescence discrimination towards chiral carboxylate anions had been studied for L1-Eu³⁺ and D1-Eu³⁺ complex and they showed good enantioselective recognition ability towards malate as ‘turn-on’ mode. The interaction of sensor L1, D1 with Eu³⁺ and L1-Eu³⁺, D1-Eu³⁺ towards malate caused different color changes in the naked eye.     

Sensitive fluorescent sensors for malate based on calix[4]arene bearing anthracene

Two chiral fluorescence receptors 3a and 3b based on calix[4]arenes were synthesized, and their chiral recognition properties for enantiomeric malate were studied by fluorescence and ¹H NMR spectra in CHCl₃. The addition of either l- or d-malate caused obvious fluorescence quenching of the host solution. Different fluorescent responses demonstrate that the two receptors have good enantioselective recognition abilities towards malate.     

A new colorimetric and fluorimetric sensor for metal cations based on poly(propilene amine) dendrimer modified with 1,8-naphthalimide

A new fluorescent first generation poly(propylene amine) dendrimer (PPI), peripherally modified with 4(butylamino-substituted-1,8-naphthalimide), has been synthesized and characterized. Its photophysical characteristics in organic solvents of different polarities were studied, and the influence of sodium hydroxide on its spectral characteristics in N,N-dimethylformamide is discussed. The complexes formed between the dendrimer and metal cations in solution have been studied with regard to the potential applications of the new dendrimer as a colorimetric and fluorescent sensor for metal ions. The fluorescence intensity of the dendrimer in the presence of metal cations (Zn²⁺, Co²⁺, Pb²⁺, Mn²⁺, Cu²⁺ and Fe³⁺) increases substantially revealing its sensor potential.     

A new fluorescent chemosensor for transition metal cations and on/off molecular switch controlled by pH

A new fluorescent chemosensor with imidazole as ionophore was synthesized by the selective derivation of calixarene, which can effectively recognize Cu²⁺ and Zn²⁺ leading to different fluoroscopic behaviors in CH₃OH-H₂O. This system could be considered as a molecular switch. By modulating the pH of the solution, on-off-on fluorescent switching is carried out upon combinatory addition of acid, base and Cu²⁺.     

Optically active macrocyclic hexaazapyridinophanes decorated at the periphery: synthesis and applications in the NMR enantiodiscrimination of carboxylic acids

A family of pyridine based dialdehydes has been efficiently prepared starting from chelidamic acid by chemical modification of its 4-hydroxyl group. The condensation of these dialdehydes with commercially available (1R,2R)-(−)-cyclohexane-1,2-diamine in the presence of Ba²⁺ template led, after the in situ reduction, to the synthesis of a family of enantiopure hexaazapyridinophanes substituted at the periphery. These new receptors have been used as chiral shift agents towards different carboxylic acids. Good splitting of the carboxylic acid NMR signals (up to ΔΔδ=0.13 ppm) were observed using substoichiometrical amount of the receptor.     

A Convenient Fluorescent Method to Simultaneously Determine the Enantiomeric Composition and Concentration of Functional Chiral Amines

A 1,1′‐bi‐2‐naphthol (BINOL)‐based chiral aldehyde in combination with Zn^II shows a highly enantioselective fluorescent response toward functional chiral amines at λ>500 nm. However, the combination of salicylaldehyde and Zn^II gives the same fluorescent enhancement for both enantiomers of a functional chiral amine at λ=447 nm. By using the fluorescent responses of the combination of the BINOL‐based chiral aldehyde, salicylaldehyde and Zn^II at the two emission wavelengths, both the concentration and enantiomeric composition of functional chiral amines such as amino alcohols, diamines, and amino acids can be simultaneously determined by a single fluorescent measurement. This work provides a simple and convenient method for chiral assay.     

A Chiral Emissive Conjugated Corral for High-Affinity and Highly Enantioselective Recognition in Water

Accurately distinguishing between enantiomeric molecules is a fundamental challenge in the field of chemistry. However, there is still significant room for improvement in both the enantiomeric selectivity (K_R(S)/K_S(R)) and binding strength of most reported macrocyclic chiral receptors to meet the demands of practical application scenarios. Herein, we synthesized a water-soluble conjugated tubular host—namely, corral[4]BINOL—using a chiral 1,1′-bi-2-naphthol (BINOL) derivative as the repeating unit. The conjugated chiral backbone endows corral[4]BINOL with good fluorescent emission (QY=34 % ) and circularly polarized luminescence (|g_lum| up to 1.4×10⁻³) in water. Notably, corral[4]BINOL exhibits high recognition affinity up to 8.6×10¹⁰ M⁻¹ towards achiral guests in water, and manifested excellent enantioselectivity up to 18.7 towards chiral substrates, both of which represent the highest values observed among chiral macrocycles in aqueous solution. The ultrastrong binding strength, outstanding enantioselectivity, and facile accessibility, together with the superior fluorescent and chiroptical properties, endow corral[4]BINOL with great potential for a wide range of applications.     

New fluorescent and colorimetric chemosensors based on the rhodamine and boronic acid groups for the detection of Hg

Novel rhodamine B (RB) derivatives bearing mono and bis-boronic acid groups were investigated as Hg²⁺ selective fluorescent and colorimetric sensors. These derivatives are first examples of reversible fluorescent chemosensors for Hg²⁺ which utilized boronic acid groups as binding sites. Two new RB-boronic acid derivatives displayed selective ‘Off-On’-type fluorescent enhancements and distinct color changes with Hg²⁺. Selective fluorescent enhancement of two rhodamine derivatives was attributed to ring opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent).     

Synthesis and complexation study of calix[4]arene diamine derivative incorporated in a polymeric backbone with chiral monomers

The novel chiral polymeric compounds containing more than one calix[4]arene have been synthesized by reacting a new calix[4]arene diamine derivative with two chiral monomers. These newly prepared compounds were studied by extraction of toxic heavy metal (Cu²⁺, Co²⁺, Cd²⁺, Hg²⁺), silver and alkali metal (Na⁺, K⁺) cations from aqueous phase. It was observed that the resulting calixarene-based polymers have a good complexing ability towards silver, alkali metal and toxic heavy metal cations.     

A circular dichroism sensor for Ni and Co based on l-cysteine capped cadmium sulfide quantum dots

A new circular dichroism sensor for detecting Ni²⁺ and Co²⁺ was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni²⁺ or Co²⁺. l-Cysteine capped cadmium sulfide quantum dots (l-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of l-Cyst-CdS QDs was significantly changed in the presence of Ni²⁺ and Co²⁺. On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni²⁺ or Co²⁺, the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10–60 μM and 4–80 μM with low detection limits of 7.33 μМ and 1.13 μM for the detection of Ni²⁺ and Co²⁺, respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni²⁺ and Co²⁺ in real water samples, and the results agreed well with the analysis using the standard ICP-OES.     

Enantioselective Fluorescent Sensors for N-Boc-Protected Amino Acid Anions Based on BINOL

The four novel derivatives of BINOL have been prepared and the structures of these compounds characterized by IR, MS, ¹H and ¹³C NMR spectroscopy and elemental analysis. The enantioselective recognition of these receptors has been studied by fluorescence titration and ¹H NMR spectroscopy. The receptors exhibited different chiral recognition abilities towards N‐Boc‐protected amino acid anions and formed 1:1 complexes between host and guest. Receptor s exhibit excellent enantioselective fluorescent recognition ability towards the amino acid derivatives.     

Enantioselective fluorescent sensors for amino acid derivatives based on BINOL bearing benzoyl unit

The derivatives of BINOL, (S)-1 and (R)-1, and their analogues have been prepared and the structures of these compounds have been characterized by IR, MS, ¹H, and ¹³C NMR spectroscopy and elemental analysis. The enantioselective recognition of these receptors has been studied by fluorescence titration and ¹H NMR spectroscopy. The receptors exhibited different chiral recognition abilities toward some enantiomers of chiral materials and formed 1:1 complexes between host and guest. Receptor (S)-1 or (R)-1 exhibits excellent enantioselective fluorescent recognition abilities toward amino acid derivatives.     

Design and synthesis of a new fluorescent tripod for chemosensor applications

A new yellow-green fluorescent tripod based 1,8-naphthalimide has been synthesized and characterised. Its photophysical properties have been investigated in organic solvents of different polarity. The effect that the metal ions (Cd²⁺, Co²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Ba²⁺, Fe³⁺ and Ag⁺) produce upon the fluorescent intensity of acetonitrile solutions of the tripod has been discussed viewing its potential applications as a detector for metal cations. The influence of protons on the fluorescence intensity of the tripod in DMF and methanol–water (1:4 v/v) solutions has also been investigated.     

Synthesis, characterization, and evaluation of rhodamine based sensors for nerve gas mimics

Six new rhodamine-B based compounds were synthesized (1-6) and used as fluorescent turn-ON sensors for diethyl chlorophosphate (DCP) in aqueous media at pH 7.0. Compound 1 and 3 gave high fluorescent enhancement with DCP compared to the other compounds. Very high selectivity and sensitivity were observed as these compounds did not show significant fluorescent enhancement with dimethyl methylphosphonate (DMMP), HCl, and metal ions, such as Na⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺. Depending on the way the sensor is presented, results are instantaneous or observed over some minutes.