Detecting H_2S Gas Concentration by 1,8-Naphthalimides Fluorescent Probe

针对传统硫化氢检测方法灵敏度低的问题,以1,8-萘酰亚胺为荧光基团,基于H₂S的还原性,通过在荧光分子结构上引入具有氧化性的硝基,合成一种可与硫化氢气体发生氧化还原反应生成有荧光响应的小分子荧光探针。该探针本身荧光十分微弱,且荧光峰值在λ=467 nm和λ=522 nm处。与H₂S反应之后,522 nm处的荧光效应消失,467 nm处的荧光效应显著增强。测定小分子荧光探针在通入H₂S气体前后的荧光光谱,分析467 nm处的荧光强度与气体浓度关系。结果表明：荧光光谱法检测出的H₂S气体浓度与荧光强度之间存在很强的线性关系,相关系数为0.979 3,最低可检测极限可达0.88×10-6 mol·L-1量级。表明基于1,8-萘酰亚胺衍生物的荧光光谱检测法可为油气田H₂S气体浓度的的快速测定提供参考。     

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.

     

一种基于3,4-二取代-1,8-萘酰亚胺和双通道响应的Cu2+荧光分子探针

设计合成了一种新型3,4-二取代-1,8-萘酰亚胺衍生物H1,在多种金属离子的水溶液中,作为铜离子的一个选择性荧光探针．该探针在甲醇和水体积比为1:1的溶液中与Cu²⁺结合,其荧光强度增强且探针的H1的吸收光谱发生红移,同时探针溶液的颜色由黄色变成粉红色．此外,探针H1与Cu²⁺结合比为1:1.     

Fluorescent Biosensor Based on Hairpin DNA Stabilized Copper Nanoclusters for Chlamydia trachomatis Detection

Chlamydia trachomatis (C. trachomatis) is a kind of intracellular parasitic microorganism, which can causes many diseases such as trachoma. In this strategy, a specific hairpin DNA with the probe loop as specific regions to recognize C. trachomatis DNA with strong affinity was designed, and its stem consisted of 24 AT base pairs as an effective template for hairpin DNA-CuNCs formation. In the absence of C. trachomatis DNA, the detection system showed strong orange fluorescence emission peaks at 606 nm. In the presence of C. trachomatis DNA, the conformation of DNA probe changed after hybridizing with C. trachomatis DNA. Then, the amount of hairpin DNA-CuNCs was reduced and resulted in low fluorescence emission. C. trachomatis DNA displayed a significant inhibitory effect on the synthesis of fluorescent hairpin DNA-CuNCs due to the competition between C. trachomatis DNA and the specific hairpin DNA. Under the optimal experimental conditions, different concentrations of C. trachomatis were tested and the results showed a good linear relationship in the range of 50 nM to 950 nM. Moreover, the detection limit was 18.5 nM and this detection method possessed good selectivity. Finally, the fluorescent biosensor had been successfully applied to the detection of C. trachomatis target sequence in HeLa cell lysate, providing a new strategy for the detection of C. trachomatis.

     

The fluorescence of polyamidoamine dendrimers peripherally modified with 1,8-naphthalimide groups: Effect of the rare earth ions and protons

We report the absorption spectra, fluorescent spectra and photophysical properties of G 2.0 polyamidoamine dendrimers with peripheral 1,8-naphthalimide groups with the hydrogen ions, the rare earth ions (Er³⁺, Tb³⁺, Nb³⁺, Eu³⁺, Yb³⁺ and Gd³⁺) and the mixture of the rare earth metal and hydrogen ions. The presence of the rare earth ions and hydrogen ions was found to enhance the fluorescence owing to the coordination between the rare earth metal or hydrogen ions and internal amido groups of polyamidoamine (PAMAM) from dendrimer. The result from the 3D isogram of the fluorescence spectra for the dendrimers with peripheral 1,8-naphthalimide groups show that it was obtained for the different emission fluorescence intensity and scope by varying the excitation wavelength and the different rare earth ions as well as its concentration. The results obtained reveal that the capacities of these systems might have acted as a sensitive label agent of the rare earth cations and protons.     

A FRET Fluorescent Sensor for Ratiometric and Visual Detection of Sulfide Based on Carbon Dots and Silver Nanoclusters

In this work, the fluorescent sensor based on fluorescence resonance energy transfer (FRET) and electrostatic interaction (EI) was prepared for the ratiometric and visual detecting S^2–. The FRET fluorescent sensor consists of two fluorophores, with carbon dots (CDs) as energy donors and silver nanoclusters (Ag NCs) as acceptors. At 390 nm excitation, CDs and Ag NCs showed two well-separated peaks at 445 nm and 660 nm, separately. The existence of S^2– caused the red fluorescence at 660 nm to be quenched, whereas the blue fluorescence at 445 nm was restored, and the fluorescence color of the ratiometric sensor changed from pink to blue. It could be employed in ratiometric and visual detecting S^2–. The linear range of quantitative detection S^2– was 0.5–100 μM, and its detection limit was 0.35 μM. CDs-Ag NCs could be used for detecting S^2– in mineral water and tap water. The results showed that the FRET ratiometric fluorescent sensor exhibits good anti-interference and high selectivity for detecting S^2– in environmental water samples.

     

4-苯乙炔-1, 8-萘酰亚胺荧光化合物的合成及电致发光性能

采用Pd(PPh₃)₂Cl₂-CuI为催化剂,Ph₃P为配体,4-溴-1,8-萘二酸酐为原料,在乙醇溶液中高收率地合成了4-苯乙炔-1,8-萘酰亚胺和4-对甲基苯乙炔-1,8-萘酰亚胺荧光新化合物。光谱研究表明,它们的最大紫外吸收波长(λ_UV,max)分别为374,380 nm,最大荧光发射波长(λ_FL,max)分别为446,462 nm,且有较高的荧光量子效率。电致发光性能测试表明,器件的最大发光亮度达到2250 cd/m²,是一类有潜在应用价值的小分子发光材料。     

Design,synthesis and sensor activity of a highly photostable blue emitting 1,8-naphthalimide

This work reports on the design, synthesis and photophysical properties of a highly photostable blue emitting 1,8-naphthalimide, containing hindered amine radical scavenger moiety and a tertiary amine cation receptor. The novel compound was configured as “fluorophore-spacer-receptor” system based on photoinduced electron transfer. Photophysical characteristics of the examined compound were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compound to detect cations was evaluated by the changes in its fluorescence intensity in the presence of metal ions (Cu²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe³⁺ and Zn²⁺) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer resulting in enhancement of the 1,8-naphthalimide fluorescence intensity. Among the tested metal ions only Cu²⁺ was efficiently detected. Also, it is clearly shown that the 2,2,6,6-tetramethylpiperidine fragment, incorporated in the structure of the novel 1,8-naphthalimide, considerably improves the sensor's photostability, sensitivity and selectivity.     

Synthesis and electroluminescent characterization of a symmetric starburst orange-red light material

A new symmetric starburst orange-red light material, tris(4-(2-(N-butyl-1,8-naphthalimide)ethynyl)phenyl)amine (TNGT), was designed and synthesized. It shows a high fluorescence quantum yield and a slight concentration-quenching effect. A high brightness (6600 cd/m²) and a high current efficiency [4.57 cd/A (at 420 cd/m²)] with CIE (0.59, 0.40) were achieved at a relatively high doping concentration (20 wt%) in a TNGT-based OLED.     

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.

     

Using a 1,8-diamino naphthalene–copper (II) system as a turn-on fluorescence probe for detecting Sudan I

An easy-to-use fluorescence probe for detecting Sudan I was developed. The probe detects Sudan I because Sudan I and 1,8-diamino naphthalene competitively interact with copper (II). Copper (II) effectively quenches the fluorescence of 1,8-diamino naphthalene because the 1,8-diamino naphthalene interacts with copper (II) and forms a 1,8-diamino naphthalene–copper (II) complex. Adding Sudan I causes the fluorescence of the system to be recovered because the Sudan I removes copper (II) from the 1,8-diamino naphthalene–copper (II) complex, liberating the 1,8-diamino naphthalene. The displacement of 1,8-diamino naphthalene by Sudan I gives a high fluorescence recovery efficiency. Under optimal conditions, the fluorescence intensity F achieved when Sudan I was added had a good linear relationship (R²?=?0.999) with the Sudan I concentration over the range 0–4.6?µM. The Sudan I detection limit was 0.032?µM. The method offers a new way of quantitatively determining Sudan I.     

A Nitronaphthalimide Probe for Fluorescence Imaging of Hypoxia in Cancer Cells

The bioreductive enzymes typically upregulated in hypoxic tumor cells can be targeted for developing diagnostic and drug delivery applications. In this study, a new fluorescent probe 4?(6?nitro?1,3?dioxo?1H?benzo[de]isoquinolin?2(3H)?yl)benzaldehyde (NIB) based on a nitronaphthalimide skeleton that could respond to nitroreductase (NTR) overexpressed in hypoxic tumors is designed and its application in imaging tumor hypoxia is demonstrated. The docking studies revealed favourable interactions of NIB with the binding pocket of NTR-Escherichia coli. NIB, which is synthesized through a simple and single step imidation of 4?nitro?1,8?naphthalic anhydride displayed excellent reducible capacity under hypoxic conditions as evidenced from cyclic voltammetry investigations. The fluorescence measurements confirmed the formation of identical products (NIB-red) during chemical as well as NTR?aided enzymatic reduction in the presence of NADH. The potential fluorescence imaging of hypoxia based on NTR-mediated reduction of NIB is confirmed using in-vitro cell culture experiments using human breast cancer (MCF?7) cells, which displayed a significant change in the fluorescence colour and intensity at low NIB concentration within a short incubation period in hypoxic conditions.

Graphical abstract

     

Comparison of Carbon Dots Prepared in Deep Eutectic Solvent and Water/Deep Eutectic Solvent: Study of Fluorescent Detection of Fe3+ and Cetirizine and their Photocatalytic Antibacterial Activity

In this study, two solvents (deep eutectic and water/deep eutectic solvents) were used for N-doped carbon dots (N-CDs) preparation by microwave irradiation. The solvent can influence surface chemical composition, quantum yield, morphology, and fluorescence of CDs. N-CDs synthesized in water/deep eutectic solvent (DES) had better quantum yield (24.5%) with respect to N-CDs synthesized in deep eutectic solvent (17.4%). These carbon dots were used as a rapid and high sensitive “off–on” fluorescent probe for the determination of Fe³⁺ ion and cetirizine. Morphology and structure of the N-CDs were characterized by FT-IR, UV–Vis, XRD and TEM. Linear range and detection limit for N-CDs synthesis in deep eutectic solvent for cetirizine were 0.08–48 µM and 15 nM, respectively and for N-CDs synthesis in water/deep eutectic solvent were 0.03–50 µM and 10 nM, respectively. Applicability of this nanoprobe was tested in cetirizine determination in serum sample. Antibacterial activities of the two synthesized N-CDs were also investigated using agar disk diffusion method.

     

Green Chemical Synthesis of N-Cholyl-L-Cysteine Encapsulated Gold Nanoclusters for Fluorometric Detection of Mercury Ions

Herein we report a simple, single-step, cost-effective, environmentally friendly, and biocompatible approach using sodium salt of N-cholyl-L-cysteine (NaCysC) capped gold nanoclusters (AuNCs) with green emission properties at above the CMC in aqueous medium under UV-light irradiation. The primary and secondary CMC of NaCysC was found to be 4.6 and 10.7 mM respectively using pyrene as fluorescent probe. The synthesized AuNCs exhibit strong emission maxima at 520 nm upon excitation at 375 nm with a large Stokes shift of 145 nm. The surface functionality and morphology of NCs are studied by fourier transform infrared spectroscopy, dymanic light scattering studies and transmission electron microscopy. The formation of AuNCs was completed within 5 h and exhibit high stability for more than 6 months. The NaCysC templated AuNCs selectively quenches the Hg²⁺ ions with higher sensitivity in aqueous solution over the other metal ions. The fluorescence analysis of Hg²⁺ showed a wide linear range from 15 to 120 µM and a detection limit was found to be 15 nM.

     

Based on charge-transfer interaction organic light-response materials: From sphere-like nanoparticles to fibers

We employed a potent and versatile ionic self-assembly (ISA) to prepare stimuli-responsive supramolecular materials using charged surfactants, N-dodecyl-4-(1-methylpip-erazine)-1,8-naphthalimide iodine [C₁₂ndi]I and oppositely charged small molecule, 4-(phenylazo)benzoic acid sodium (PBAS). By transmission electron microscopy, nanospheres could be observed to transform into nanofibers upon irradiated with UV light (365 nm) for 1 h. The UV–vis absorption spectra and fluorescence spectra of the fibers indicate that charge-transfer interaction is regarded as the driving force for the formation of fibers. Density functional theory (DFT) calculations prove that the π–π stacking and electrostatic interactions between [C₁₂ndi]I and PBAS contributes significantly to the resulting aggregates. The supramolecular fibers have the potential applications in some fields, e.g. drug delivery and electro-optical devices.     

Spectroscopic and Photophysical Characterization of Fluorescent Chemosensors for Monosaccharides Based on N-Phenylboronic Acid Derivatives of 1,8-Naphthalimide

Spectroscopic and photophysical properties of two fluorescent probes for monosaccharides are presented. Probes are based on the N-phenyl-1,8-naphthalimide structure having the boronic acid group [R-B(OH)₂] in ortho in one case, and meta in the other case, positions of the N-phenyl group. Formation of the anionic form of the boronic acid group [R-B(OH)^– ₃] induced a substantial decrease of the steady-state fluorescence of both compounds. Because no change in the fluorescence lifetime from the neutral to the anionic forms is observed, static quenching resulting from photoinduced electron transfer from the anionic form of the boronic acid is used to explain the decrease of the emission intensity. Both compounds show substantial decreases of their fluorescence intensity in the presence of sugars. In addition, this decrease of the fluorescence intensity is associated with an increase of the fluorescence lifetime for the ortho derivative while no effect on the lifetime is observed for the meta derivative. Both photoinduced electron transfer and steric hindrance are discussed to correlate the observed results.     

Ratio-metric sensor to detect riboflavin via fluorescence resonance energy transfer with ultrahigh sensitivity

In this paper, a novel fluorescence resonance energy transfer (FRET) ration-metric fluorescent probe based on heteroatom N, S doped carbon dots (N, S-CDs) was developed to determine riboflavin in aqueous solutions. The ratio of two emission intensities at different wavelengths is applied to determine the concentration of riboflavin (RF). This method is more effective in reducing the background interference and fluctuation of diverse conditions. Therefore, this probe obtains high sensitivity with a low limit of detection (LOD) of 1.9 nM (0.7 ng/ml) which is in the highest level of all riboflavin detection approaches and higher than single wavelength intensity detection (1.9 μM). In addition, this sensor has a high selectivity of detecting riboflavin in deionized water (pH=7) with other biochemical like amino acids. Moreover, riboflavin in aqueous solution is very sensitive to sunlight and can be degraded to lumiflavin, which is toxic. Because the N, S doped carbon dots cannot serve as an energy donor for N, S doped carbon dots and lumiflavin system, this system makes it easy to determine whether the riboflavin is degraded or not, which is first to be reported. This platform may provide possibilities to build a new and facile fluorescence resonance energy transfer based sensor to detect analytes and metamorphous analytes in aqueous solution.     

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.

     

Highly Selective Detection of Al3+ by Carboxamide-Based Fluorescent Chemosensor

We designed a carboxamide-based fluorescent chemosensor HTPQ ((E)-2-(((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)methylene)amino)thiophene-3-carboxamide) for detecting Al³⁺. HTPQ could probe Al³⁺ by fluorescence enhancement. Limit of detection for Al³⁺ toward HTPQ was 1.4 μM. Binding of HTPQ to Al³⁺ was determined to be a 1:1 ratio with the analysis of Job plot and ESI-mass. In addition, HTPQ was able to detect Al³⁺ using the test strip by fluorescent variation. The sensing process of Al³⁺ by HTPQ was presented by UV–vis titration, ESI–MS, Job plot, ¹H NMR titration and DFT calculation.

     

萘酰亚胺铁离子荧光探针的合成及识别性能

以1,8-萘酐、N,N-二甲基乙醇胺、三乙烯四胺为原料,通过酰亚胺化、缩合等反应,合成一种萘酰亚胺荧光探针,并通过核磁氢谱、红外光谱结构表征,测定了探针在乙醇与水的混合溶液中的荧光光谱。考察了金属离子浓度等因素的影响,对其配位机理进行了研究。结果显示,目标产物在乙醇-水溶液中对Fe~(3+)表现出了专属选择性识别性能,在(1.87~6.53)×10~(-6)g/m L的Fe~(3+)浓度范围内,探针荧光强度与Fe~(3+)浓度有很好的线性关系,线性相关系数R=0.995 3,检出限为405.1 ng/mL。