Synthesis and Investigation of Derivatives of 1,8-Naphthalimide with a Red Emission via an Aromatic Nucleophilic Substitution Reaction

1,8-Napthalimides (NIs) have been widely used as fluorescent molecules in biological, chemical, and medical fields because NIs shows high stability and various fluorescence properties under different conditions. However, NIs typically display a fluorescence emission wavelength in the range of 350 – 550 nm which can be notably interfered with by autofluorescence in living cells, significantly limiting their bio-applications. Moreover, low solubility in aqueous media is another major limitation for NIs. In this project, four derivatives of NIs (1–4) have been synthesized via an aromatic nucleophilic substitution reaction and their photophysical properties have been investigated in various media (water, MeOH, MeCN, DMSO, EtOAc, and THF). All of these derivatives (1–4) show a long emission wavelength around 600 nm and high solubility in polar solvents. Particularly molecules (1–4) show the longest emission (624–629 nm) in water and the fluorescence intensity is not significantly varied in the range of pH 4–11. These unique features, long emission wavelength, high solubility, and high stability in difference pH media, will allow these derivative (1–4) to be used as excellent labeling reagents in the biological system.

     

A Rapid Near-Infrared Fluorescent Probe for Cysteine Based on Isophorone and its Application in B16 Cell Imaging

A novel near-infrared fluorescent probe SWJT-5 based on dicyanoisophorone was synthesized. It achieved the rapid (within 40 s) and discriminative detection of Cys over Hcy and GSH with a large Stokes shift (205 nm). It showed high selectivity and sensitivity for Cys, and had an obvious enhancement of fluorescence emission. The detection limit was 0.43 μM. This probe also had low background interference and little damage to biological samples. Therefore, SWJT-5 had been applied to bioimaging in living cells successfully.

     

Two Mn(II) and Zn(II) Coordination Polymers: Aqueous-Phase Detection of Nitroaromatic Explosives and Protective Effect on Atherosclerosis

Via the solvothermal reaction between Zn(II) or Mn(II) salts and 5-(3,4-dicarboxylphenoxy)nicotinic acid (H₃L) ligand, a trifunctional N,O-building block having three diverse kinds of functional groups (O-ether, N-pyridyl and COOH), two new coordination polymers (CPs) could be generated, and their chemical formulae respectively are {[Mn₃(L)₂(H₂O)₂]·4H₂O} (1) and {[Zn(HL)]·NMP} (2). The complex 2 based on Zn(II) possesses high efficiency of fluorescence quenching for the nitrophenol (2,4,6-trinitrophenol, TNP; 4-nitrophenol, 4-NP; 3-nitrophenol, 3-NP; 2-nitrophenol, 2-NP) in the aqueous solution. Furthermore, the treatment activity of compounds on the atherosclerosis was assessed, and relevant mechanism was investigated. First of all, the ELISA assay was used to measure the content of the inflammatory cytokines released into the plasma. Besides, the levels of the NF-κb signaling pathway in the vascular endothelial cells were measured with real time RT-PCR. The hemolysis test was conducted in this research to measure the biocompatibility of the new compound.

     

Enhanced Fluorimetric Determination of Samarium with Dibenzoylmethane and Diphenylguanidine by Gadolinium

Abstract

The fluorescence of Sm-dibenzoylmethane (DBM)-diphenylguanidine (DPG) system was enhanced by about two to three orders of magnitude when it was excited in the presence of Gd in ethanol-water solution. The excitation and emission wavelegths were 390 nm and 652 nm, respectively. The fluorescence intensity was a linear function of the concentration of Sm in the range of 1.0 × 10^?9–2.0 × 10^?6 M. The fluorescence mechanism of the system is discussed.     

Uracil-Appended Fluorescent Sensor for Cu2+ and Hg2+ Ions: Real-Life Utilities Including Recognition of Vitamin B2 (Riboflavin) in Milk Products and Invisible Ink Applications

A simple uracil-appended fluorescent sensor (1) has been developed by one pot reaction and characterized by using common spectroscopic methods such as UV-vis, Fluorescence, HRMS and FT-IR analyses. Upon addition of various metal ions to the CH₃CN solution of sensor 1, the fluorescence was quenched in the presence of Cu²⁺ / Hg²⁺ ions. The limit of detection for Cu²⁺ and Hg²⁺ was calculated to be 3.31 and 0.316 µM, respectively. Further, the sensor was applied for real-life applications in the determination of Vitamin B₂ (riboflavin) and its presence in milk products. With the incorporation of different sources of vitamin-B to acetonitrile solution of it, there was discernible fluorescence enhancement only in the presence of vitamin B₂. Also, it has been successfully applied for the detection of Vitamin B₂ (riboflavin) in milk and curd. Moreover, based on the fluorescent color changes, the sensor was utilized for invisible ink applications.

     

Spectroscopic Investigation on the Charge—Transfer Complex of 2,4,6—Trinitrophenol with the Polycyclicamine 1,4,8,11-Tetraazacyclotetradecane

Abstract

The reaction between 2,4,6-trinitrophenol(TNP) and the polycyclicamine 1,4,8,11-tetraazacyclotetradecane (TACTD) in solvents such as chloroform and carbontetrachloride have been studied spectrophotometrically using UV—VIS, and IR methods. The results indicate the formation of a 1:2 charge—transfer complex with formula((TACTD)(TNP)₂). The charge-transfer absorption in this complex appears arounds 410 nm. The values of both the equilibrium constant, K, and the molar extinction coefficient, ?, for the reaction in different solvents are calculated for the CT-complex. These values were used to understand the solvent effects on the course of the reaction. All observed infrared bands for the formed solid complex are assigned.     

A New Benzothiazin-functionalized Calix[4]arene-based Fluorescent Chemosensor for the Selective Detection of Co2+ Ion

Calixarenes, which have a great place in supramolecular chemistry, have become the most prominent macrocyclic compounds in synthetic organic chemistry due to their easy synthesis and functionalization. In this study, p-tert-butyl calix[4]arene dihydrazide derivative was synthesized and then reacted with 3-oxo-3,4-dihydro-2 H-benzo[b][1,4] thiazin-2-ylideneacetyl chloride to prepare new calixarene based chromophore compound 4. The structure of the synthesized compound was elucidated by spectroscopic methods such as ¹H NMR ¹³C NMR and FT-IR spectroscopy. Chromogenic and fluorescence properties of compound 4 were evaluated. It was observed from both studies that compound 4 was Co²⁺ selective and shows fluorescence Switched-off behavior. Stoichiometry, binding constant and the detection limit were calculated. The stoichiometry between compound 4 and Co²⁺ was found to be 1:1. The binding constant value (K) was calculated as 666.67 M^??1 using Benesi–Hildebrand equation, while the detection limit for Co²⁺ ion was calculated as 0.0465 µM.

     

Interctions of laurdan with membranes at high pressures

Abstract

The fluorescence emission spectra of Laurdan in egg yolk phosphatidylcholine vesicles were measured as a function of pressure. The results suggest that the long hydrocarbon side chain stabilizes Laurdan in bilayers at high pressures.     

Chemical Vapor Generation with Slurry Sampling: A Review of Applications to Atomic and Mass Spectrometry

Abstract

A critical review of published analytical methods and techniques for chemical vapor generation (CVG) with slurry sample introduction for detection by atomic and mass spectrometry is presented. The nstrumentation used for the reaction as well as separation and transport of the species, influence of chemical and physical factors, and efficiency of the process are considered. A brief comparison of detection limits obtained with atomic absorption, emission, and fluorescence as well as mass spectrometry along with practical applications to analytical samples are summarized. The current state-of-the-art, including advantages and limitations of this approach, is discussed.     

A Coumarin-Based Fluorescent Chemosensor for Zn<Superscript>2+</Superscript> in Aqueous Ethanol Media

A coumarin-based fluorescent chemosensor 1 for Zn²⁺ was designed and synthesized. Compound 1 exhibits lower background fluorescence due to intramolecular photoinduced electron transfer. However, upon mixing with Zn²⁺ in 30% (v/v) aqueous ethanol, a “turn-on” fluorescence emission is observed. The fluorescence emission increases linearly with Zn²⁺ concentration in the range 0.5–10 μmol L⁻¹ with a detection limit of 0.29 μmol L⁻¹. No remarkable emission enhancement was, however, observed for other metal ions. The proposed chemosensor was applied to the determination of Zn²⁺ in water samples with satisfactory results.     

In Light of Recent Developments,Application of Fluorescence Spectral Analysis in Tumor Diagnosis

Abstract

This paper reviews the background to cancer tumors. Fluorescence spectral analysis has been quantitatively applied to the detection of protoporphyrin IX (Pp‐IX) in transplanted squamous cell carcinoma (SCC) tissue and intra‐operative brain astrocytoma (glioblastoma) tissue after the administration of 5‐aminolevulinic acid (5‐ALA). Coincidence with the emission spectra of Pp‐IX incorporated into the tumor tissues (cryo‐sections) and a standard Pp‐IX in the miceller solution was confirmed. A calibration curve of the fluorescence intensity of Pp‐IX against a known concentration standard of Pp‐IX was established. From the fluorescence detection method (calibration curve), it was found that the longer alkyl‐chain length (methyl‐ and hexyl‐) 5‐ALA induced Pp‐IX in the SCC tissue. Furthermore, an ultrasound treatment enhanced the uptake of Pp‐IX during the topical administration of 5‐ALA derivatives. In the case of intra‐operative observation for the fluorescence intensity of Pp‐IX in the brain astrocytoma tissue, this quantitative detection in the cryo‐section demonstrated the intra‐operative observation for the fluorescence intensities (?, +/?, +, ++, +++) diagnosis was correlated closely with the grades of astrocytoma. The intensity increased exponentially with the cancer grades. In future, fluorescence spectral diagnosis of Pp‐IX in the tumor will be very useful for other clinical diagnosis of tumors using 5‐ALA.     

Steady‐State and Time‐Resolved Emission Studies of 6‐Methoxy Quinoline

Abstract

Steady‐state absorption, fluorescence excitation, and emission spectra of 6‐methoxy quinoline (6‐MQ) were measured at room temperature in cyclohexane, dioxane, ethanol, acetonitrile, water, and water–dioxane solvents. Absorption spectra of cyclohexane, n‐hexane, and isopentane solutions show resolved vibronic structure at room temperature. However, the excitation spectrum of cyclohexane solution is structureless and is found to be emission wavelength dependent, indicating the formation of at least two distinct species in the ground state. Similar behavior was observed in dioxane and water–dioxane solutions. For all other solutions, the fluorescence excitation spectrum of 6‐MQ was found to be the same for different emissions. Emission of 6‐MQ in all solvents consisted of two bands with their maxima around 355 nm (I) and 430 nm (II), the actual positions and the relative intensities being dependent on the solvent used. The bands I and II were respectively attributed to normal and protonated/H‐bonded species of either ¹L_a or ¹L_b states or mixed (¹L_a/¹L_b) state of ππ* character. Fluorescence decay of this dye in all solvents monitored over each emission maximum showed biexponential behavior, and the analysis yielded two different lifetime components for each emission band. The short and long fluorescence decay components were respectively in the range of 0.30–3.00 ns and 18–20 ns. The observed emission characteristics coupled with the nature of the fluorescence polarization spectra and two different decay components for each emission suggest the existence of two different conformers having two different excited electronic states.     

Pressure Effect on Solvation Dynamics and Rotational Dynamics in Solution

Effects of pressure on solvation dynamics and rotational dynamics in solution were studied by picosecond time-dependent fluorescence Stokes shift (TDFSS) and picosecond time-dependent fluorescence rotational depolarization (TDFRD). The fluorescence lifetimes of solute probes, coumarin 153 and p -terphenyl, in various solvents were measured at high pressures by time-correlated single photon counting (TCSPC) technique with time resolution of 20-30 ps.     

A Chemosensing Ensemble for the Detection of Cysteine Based on the Inner Filter Effect Using a Rhodamine B Spirolactam

A fluorescent chemosensing ensemble for the detection of cysteine is designed based on the fluorescence inner filter effect. The method employs the coordination of Cu²⁺ ion with salicylaldehyde rhodamine B hydrazone (I), a colorless and non-fluorescent rhodamine B spirolactam derivative to form I-Cu(II), a pink color but weakly fluorescent complex. When rhodamine B was introduced to the I-Cu(II) complex solution, the fluorescence signal of rhodamine B is dramatically decreased because of the fluorescence inner filter effect (IFE). Upon adding cysteine to the above solution, it can complex preferentially to Cu²⁺ compared to I, and the I-Cu(II) complex dissociates, which thus decreases the fluorescence IFE of the solution, and in turn leading to the fluorescence increase of the chemosensing system. Based on the above mechanism, a fluorescent chemosensing ensemble for cysteine is developed. The fluorescence increase is linearly with cysteine concentration up to 10.0 μ mol L⁻¹, with a detection limit of 1.4 × 10⁻⁷ mol L⁻¹ (3σ). The optimal conditions of the proposed method were studied and the selectivity of the proposed method was investigated in this paper.     

Sensitive Detection of Luteolin Using Thioglycolic Acid–Capped Cadmium Telluride/Cadmium Sulphide Quantum Dots as the Fluorescent Probe

ABSTRACT

A sensitive and simple method for the determination of luteolin (LTL) was developed based on the fluorescence quenching effect of LTL for thioglycolic acid–capped (TGA-capped) CdTe/CdS quantum dots (QDs). Under optimum conditions, a good linear relationship was obtained from 0.3 to 20.0 µg · mL^?1 with a correlation coefficient of 0.9972, and the detection limit was 7.2 ng · mL^?1. The fluorescence quenching mechanism has been proposed on the basis of electron transfer supported by ultraviolet-visible (UV-Vis) absorption, fluorescence (FL) spectroscopy. The proposed method was successfully applied to the determination of LTL in commercial capsules and human urine samples. It manifested several advantages such as high sensitivity, short analysis time, low cost, and ease of operation.     

Highly Sensitive ‘on–off’ Pyrene Based AIEgen for Selective Sensing of Copper (II) Ions in Aqueous Media

A Fluorescent chemosensor based on pyrene scaffold, 5-diethylamino-2-(pyren-1-yliminomethyl)-phenol (PDS) is synthesized using condensation method. It displays novel aggregation-induced emission (AIE) phenomena in its aggregated/solid state. The AIE characteristic of PDS is studied in CH₃CN/H₂O mixtures at different volume percentage of water and morphology of the aggregated particles are investigated by DLS and optical fluorescence microscopic study. The probe is aggregated into ordered one-dimensional (1-D) rod like microcrystals and exhibit high efficiency of solid-state emission with green colour. By taking advantage of its interesting AIE feature, the aggregated hydrosol has been utilized as ‘off–on’ type fluorescence switching chemosensor with superb selectivity and sensitivity towards Cu²⁺ions and the limit of detection (LOD) was calculated as low as 6.3 µM. A high Stern–Volmer quenching constant was estimated to be 2.88?×?10⁵ M^?1. The proposed chemosensor with AIE feature reveals a prospective view for the on-site visual recognition of Cu²⁺ ions in fluorescent paper strips and the synthesized probe is also exploited to find out the concentration of Cu²⁺ions in real water samples.

     

The Schiff Base Probe With J-aggregation Induced Emission for Selective Detection of Cu2+

Here, three Schiff bases 3a-c, differing by the substitutions (–H, –Cl, and –N(CH₃)₂) on the phenyl ring, have been designed and synthesized via the reaction of ortho-aminophenol with benzaldehyde, 2,4-dichlorobenzaldehyde and para-dimethylamine benzaldehyde in 1:1 molar ratio with favourable yields of 89–92%, respectively. Their structural characterizations were studied by FT-IR, NMR, MALDI-MS and elemental analysis. The fluorescence behaviours of compounds 3a and 3b exhibited a severe aggregation caused quenching (ACQ) effect in EtOH/water system. On the contrary, compound 3c had an obvious J-aggregation induced emission (AIE) feature in EtOH/water mixture (v/v?=?1:1), and exhibited excellent sensitivity and anti-interference towards Cu²⁺ with the limit of detection (LOD) of 1.35?×?10^–8 M. Job’s plot analysis and MS spectroscopic study revealed the 2:1 complexation of probe 3c and Cu²⁺. In addition, probe 3c was successfully applied to the determination of Cu²⁺ in real aqueous samples.

     

Solid-Surface Room Temperature Phosphorescence

Abstract

Luminescence can be defined as radiation emitted from atoms or molecules as they undergo a radiative transition from an excited state to a lower energy state. After the absorption of incident radiation, the emission of a photon during the radiative transition is called photoluminescence. The process of photoluminescence encompasses both fluorescence and phosphorescence.     

One step synthesis of ultra-high quantum yield fluorescent carbon dots for “on-off-on” detection of Hg2+ and biothiols

In this paper, the carbon dots (CDs) with strong blue fluorescence were synthesized through hydrothermal method, which using folic acid, ammonium citrate and ethylenediamine as precursors. The prepared CDs with a high absolute quantum yield of 81.94% and showed excellent stability in high concentration salt solution and different pH conditions. With the addition of Hg²⁺, the signal of CDs was selectively quenched. At the same time, the CDs-Hg²⁺ system could be recovered after the introduction of biothiols. Moreover, the fluorescence of CDs showed a good linear relationship with Hg²⁺ (1–15 µM), and the detection limit as low as 0.08 µM. In addition, the prepared CDs with low toxicity could be used to detect Hg²⁺ in living cells and actual water samples.

     

A Benzothiazole-Based Fluorescence Turn-on Sensor for Copper(II)

A new benzothiazole-based chemosensor BTN (1-((Z)-(((E)-3-methylbenzo[d]thiazol-2(3H)-ylidene)hydrazono)methyl)naphthalen-2-ol) was synthesized for the detection of Cu²⁺. BTN could detect Cu²⁺ with “off-on” fluorescent response from colorless to yellow irrespective of presence of other cations. Limit of detection for Cu²⁺ was determined to be 3.3 μM. Binding ratio of BTN and Cu²⁺ turned out to be a 1:1 with the analysis of Job plot and ESI-MS. Sensing feature of Cu²⁺ by BTN was explained with theoretical calculations, which might be owing to internal charge transfer and chelation-enhanced fluorescence processes.