Highly selective fluorescence turn-on determination of fluoride ions via chromogenic aggregation of a silyloxy-functionalized salicylaldehyde azine

A novel fluorescent chemsensor TBS-protected salicylaldehyde azine (TSAA) for fluoride ion was developed based on aggregation-induced emission (AIE). The probe TSAA was prepared by the reaction of salicylaldehyde azine (SAA) with tert-butyldimethylsilyl chloride (TBS-Cl) via an unusual synthetic methodology and shows only non-emission. Upon treatment with fluoride in aqueous MeCN solution, the TBS protective group of probe TSAA was removed readily and the fluorescence of the probe was switched on, which resulted in a new fluorescence peak around 543 nm. The fluorescent intensity at 543 nm increases linearly with fluoride ion concentration in the range 1–50 μmol L^?1. This proposed probe shows excellent selectivity toward fluoride ion over other common anions and cations.     

Ovalbumin-stabilized gold nanoclusters with ascorbic acid as reducing agent for detection of serum copper

Ovalbumin-stabilized gold nanoclusters(OVA@AuNCs) were prepared with ascorbic acid as a reducing agent. This strategy could realize the synthesis of water-soluble OVA@AuNCs within 20 min. The asprepared fluorescent probe showed a red fluorescence emission at 630 nm. Moreover, the properties of the OVA@AuNCs were characterized by transmission electron microscope, dynamic light scattering,ultraviolet-visible spectroscopy, fluorescent spectroscopy. Based on the surface electron density decrease-induced fluorescence quenching mechanism, the OVA@AuNCs provided high sensitivity and selectivity for sensing copper ions. A good linear relationship was obtained between the fluorescence intensity of OVA@AuNCs and the concentration of copper ions in the range of 5.0-100.0 μmol/L(R~2=0.999) with a detection limit of 640 nmol/L Furthermore, the rat serum copper contents were determined by using the OVA@AuNCs based assay, indicating great potential of fluorescent probes for application in biological and clinical analysis.     

Red-emitting salicylaldehyde Schiff base with AIE behaviour and large Stokes shift

Three salicylaldehyde Schiff base (SSB) with AIE behavior were designed and facilely synthesized through a condensation reaction. In solid and aggregation states, these SSB dyes exhibited yellow to red emission with large Stokes shift. One of SSB dyes could specifically stain lipid droplets in living cells.     

A simplistic one-pot method to produce magnetic graphene-CdS nanocomposites

A simple, yet novel process was developed where magnetic graphene-CdS (Fe₃O₄-CdS/G) nanocomposites were prepared by a one-pot solvothermal route in which the reduction of graphite oxide (GO) into graphene was accompanied by the generation of CdS and Fe₃O₄ nanoparticles. The results of TEM and XRD studies indicate the formation of Fe₃O₄-CdS/G nanocomposites. Besides vibration sample magnetometry, fluorescence spectra and loading of doxorubicin (DOX) reveal that this new nanocomposite possesses good superparamagnet (44.85 emu/g), good fluorescent properties and a high loading efficiency (0.98 mg/mg). The efficient, stable, and water soluble nanocomposites are confirmed to be suitable for biomedical applications.     

Imidazo[1,5-α]pyridine-derived fluorescent turn-on probe for cellular thiols imaging with a large Stokes shift

We presented the design, synthesis and preliminary evaluation of the 2,4-dinitrobenzenesulfonate (DNBS) of imidazo[1,5-α]pyridine derivative, NIPY-DNBS, as a turn-on fluorescent probe for the detection of thiols in aqueous solution. The reaction mechanism was confirmed by means of fluorescence, absorption and HRMS. The large Stokes shift (201 nm), high sensitivity (the detection limit for Cys was calculated to be as low as 0.17 μM) and fast response (10 min) of NIPY-DNBS make it a practical and reliable method for fluorescence imaging. Furthermore, application of NIPY-DNBS for the selective detection of intracellular thiols has been successfully demonstrated in living A549 cells.     

A pillar[5]arene-based side-chain pseudorotaxanes and polypseudorotaxanes as novel fluorescent sensors for the selective detection of halogen ions

A pseudorotaxane and its polypseudorotaxanes formed between pillar[5]arene moieties and noctylpyrazinium cations as novel fluorescent sensors for the selective detection of halogen ions were reported.A collapse of these pillar[5]arene-based pseudorotaxanes and polypseudorotaxanes occurred upon the addition of Cl,Br,and I（tetrabutylammonium salts）,respectively,leading to their fluorescence recovery.The fluorescence enhancement of the pseudorotaxane and the polypseudorotaxanes increases in the order of I     

Studies on the interaction between imidacloprid and human serum albumin: Spectroscopic approach

The interaction between imidacloprid (IMI) and human serum albumin (HSA) was investigated using fluorescence and UV/vis absorption spectroscopy. The experimental results showed that the fluorescence quenching of HSA by IMI was a result of the formation of IMI–HSA complex; static quenching was confirmed to result in the fluorescence quenching. The apparent binding constant K_A between IMI and HSA at three differences were obtained to be 1.51 × 10⁴, 1.58 × 10⁴, and 2.19 × 10⁴ L mol^?1, respectively. The thermodynamic parameters, ΔH° and ΔS° were estimated to be 28.44 kJ mol^?1, 174.76 J mol^?1 K^?1 according to the van’t Hoff equation. Hydrophobic interactions played a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (IMI) was obtained according to fluorescence resonance energy transfer. The effect of IMI on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy CD and three-dimensional fluorescence spectra, the environment around Trp and Tyr residues were altered.     

Rational construction of self-assembly azobenzene derivative monolayers with photoswitchable surface properties

hoto-responsive azobenzene (ABZ) derivatives with different end groups (R) were employed to construct selfassembled monolayers (SAMs) on silicon substrates. The SAMs based on hydrophilic (4-(4'-aminophenylazo) benzoic acid, ABZ-COOH) show excellent reversible photoswitching performance with a large contact angle change of 35° under optimized process.     

PbO@C core–shell nanocomposites as an anode material of lithium-ion batteries

In this study, the electrochemical performance of PbO@C core–shell nanocomposites as an anode material of lithium-ion batteries was reported. The PbO@C nanocomposites were prepared via the pyrolysis of lead benzoate precursor. Compared to the reported Pb-based anodes, the PbO@C nanocomposites exhibited higher reversible capacity and longer cycling life. A reversible capacity of 170 mAh g^?1 could be maintained after discharging/charging for 50 cycles, which was at least 1.5 times than the previously reported values. The enhanced electrochemical performance was attributed to the presence of carbon shells that could alleviate the large volume-change of Pb particles during the alloying/dealloying process.     

Fluorescence and DNA-binding spectral studies of neodymium(III) complex containing 2,2′-bipyridine, [Nd(bpy)2Cl3·OH2]

The interaction of [Nd(bpy)₂Cl₃·OH₂], where bipy is 2,2′-bipyridine, with DNA has been studied by absorption, emission, and viscosity measurements. [Nd(bpy)₂Cl₃·OH₂] showed absorption decreasing in charge transfer band with increasing of DNA. The binding constant, K_b has been determined by absorption measurement and found to be (1.5 ± 0.1) × 10⁵ M^?1. The fluorescent of [Nd(bpy)₂Cl₃·OH₂] has been investigated in detail. The interaction was also studied by fluorescence quenching technique. The results of fluorescence titration revealed that DNA had the strong ability to quenching the intrinsic fluorescence of Nd(III) complex at 327 nm. The binding site number n, apparent binding constant K_b and the Stern–Volmer quenching constant K_SV have been determined. Thermodynamic parameters have been calculated according to relevant fluorescent data and Van’t Hoff equation. Characterization of bonding mode has been studied. The results suggested that the major interaction mode between [Nd(bpy)₂Cl₃·OH₂] and DNA was groove binding.     

Fluorescence quenching of triazatruxene-based glycocluster induced by peanut agglutinin lectin

A novel triazatruxene-based fluorescent glycocluster was synthesized and its selective binding interactions with PNA lectin were investigated by fluorescence spectroscopy,CD spectroscopy,and a turbidity assay.The glycocluster exhibited a strong binding affinity for PNA lectin with a Stern-Volmer quenching constant of 5.8×10⁵ mol^-1L     

A fluorescent sensor for Al3+ based on a photochromic diarylethene with a hydrazinobenzothiazole Schiff base unit

A new fluorescent turn-on chemosensor for Al³⁺ based on a diarylethene unit was designed and synthesized. Photochromism, fluorescence switch, and metal ion recognition behaviors of this diarylethene derivative were investigated by absorption and fluorescence emission spectra. It shows an outstanding fluorometric sensing ability toward Al³⁺ ion, and the detection limit was measured to be 9.3 × 10^?8 mol L^?1 via fluorescence methods. Based on these interesting properties, a combinational logic circuit was constructed successfully.     

LIF technique offers the potential for the detection of cadmium-induced alteration in photosynthetic activities of Zea Mays L.

The laser-induced fluorescence spectra of leaves of Zea mays L. plants treated with different concentrations (0.01, 0.10 and 1.00 mM) of cadmium were recorded in region 650–800 nm using 488 nm line of Argon Ion laser as excitation source and PMT as detector. Besides this, blue-green fluorescence and Chl fluorescence were also measured using third harmonic (355 nm) of Nd:YAG laser as excitation source and 320 M monochromator with intensified charge coupled device as a detector in the region 400–800 nm. These spectra have been used to analyse the effect of several doses of cadmium on the photosynthetic activities of Z. mays L. plants. The fluorescence intensity ratios (FIR) of control as well as treated Z. mays L. were calculated by evaluating curve-fitted parameters using Gaussian spectral function. In addition, growth parameters like photosynthetic pigments content were also estimated. The chlorophyll fluorescence intensity ratio F685/F735 excited by both 488 and 355 nm lines are strongly correlated with photosynthetic pigments content (total chlorophyll and carotenoids) and their ratios. Consequently, there also existed a correlation between the blue-green fluorescence intensity ratio F470/F540 and photosynthetic pigments content.     

Effect of radiation dose on the properties of natural rubber nanocomposite

Effect of radiation dose and carbon nanotubes (CNT) on the mechanical properties of standard Malaysian rubber (SMR) was investigated in this study. SMR nanocomposites containing 1–7 phr CNT were prepared using the solvent casting method and the nanocomposites were radiated at doses of 50–200 kGy. The change in mechanical properties, especially, tensile strength (Ts), elongation at break (Eb), hardness and tensile modulus at 100% elongation (M₁₀₀) were studied as a function of radiation dose. The structure and morphology of reinforced natural rubber was investigated by FESEM, TEM and AFM in order to gain further evidence on the radiation-induced crosslinking. It was found that the Ts, M₁₀₀ and the hardness of the SMR/CNT nanocomposites significantly increased with radiation dose; the elongation at break exhibited an increase up to 100 kGy, and a downward trend thereafter. Results on gel fraction further confirmed the crosslinking of SMR/CNT nanocomposites upon radiation.     

Preparation of a poly(methyl methacrylate)-reduced graphene oxide composite with enhanced properties by a solution blending method

Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by a simple solution blending method. The glass transition temperature of the produced PMMA/graphene composite was increased by 37 °C with 1.0 wt.% RGO content, which is approximately 40% of improvement compared to that of pure PMMA. The thermal expansion coefficient (TEC) decreased by 68% with as low as 0.1 wt.% RGO loading. The electrical conductivity of the nanocomposites reached up to 0.037 S/m even with only 2.0 wt.% RGO, which increased by more than twelve orders of magnitude. The resulting nanocomposites showed that a stable colloidal suspension of graphene dispersion in organic solvent before blending with PMMA is necessary to fabricate the nanocomposites with enhanced properties.     

A simple and sensitive assay for apurinic/apyrimidinic endonuclease 1activity based on host-guest interaction of β-cyclodextrin polymer and pyrene

A simple and sensitive method for APE1 activity detection was developed based on fluorescence enhancement of pyrene in the presence of β-cyclodextrin polymer.     

Fluorescence “turn-on” chemosensor for the selective detection of zinc ion based on Schiff-base derivative

N,N′-phenylenebis(salicylideaminato) (L) has been used to detect trace amounts of zinc ion in acetonitrile–water solution by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to zinc ions in MeCN/H₂O (1:1, v/v) solution. The fluorescence enhancement of L is attributed to the 1:1 complex formation between L and Zn(II), which has been utilized as the basis for selective detection of Zn(II). The linear response range for Zn(II) covers a concentration range of 1.6 × 10^?7 to 1.0 × 10^?5 mol/L, and the detection limit is 1.5 × 10^?7 mol/L. The fluorescent probe exhibits high selectivity over other common metal ions, and the proposed fluorescent sensor was applied to determine zinc in water samples and waste water.     

Electrochemical fabrication of novel fluorescent polymeric film: Poly(pyrrole–pyrene)

We describe herein the electrochemical characterization and polymerization of 4-pyren-1-yl-butyric acid 11-pyrrol-1-yl-decyl ester (pyrrole–pyrene) in CH₃CN. The electrochemical oxidation of the pyrrole group at 0.77 V vs Ag/Ag + 10 mM in CH₃CN led to the first example of a fluorescent polypyrrole film. The mechanism of deposition on platinum electrode was studied by voltammetry and chronoamperometry. The optical properties of the polymeric films electrogenerated on ITO electrodes were examined by UV–visible spectroscopy and fluorescence microscopy indicating an increase in fluorescence properties by increased polymer thickness. The electrochemical oxidation of pyrenyl group linked to the polypyrrole backbone was carried out at 1.2 V. This additional polymerization was demonstrated by UV–visible spectroscopy and induced the loss of the fluorescence properties of the resulting polymeric film.     

Experimental and theoretical study of a new carbazole derivative having terminal benzimidazole rings

A novel intramolecular donor–acceptor compound has been synthesized and characterized. This compound was a symmetrical A–π–D–π–A type molecule containing two benzimidazole rings as two electron acceptors (A) and an N-ethylcarbazole group as electron donors (D). The absorption and emission spectra of the compound were determined by experimental methods in solution and were computed by using the density functional theory (DFT) and the time-dependent density functional theory (TDDFT) in gas phase and in chloroform solution. The calculated absorption and emission wavelengths were in good agreement with the experimental ones. The fluorescence quantum yields and fluorescence lifetimes of the compound in several solvents have been studied by means of steady state and time resolved fluorescence. The results showed the compound had high quantum yield. The cross-section of two-photon absorption (TPA) of the compound was measured by using femtosecond laser in dichloromethane solution. The result indicated the cross-section maximum of two-photon absorption was 430 GM at 600 nm. These results made the compound of great interest as a new fluorescent probe and photoluminescence material.     

A rapid method for the detection of humic acid based on the poly(thymine)-templated copper nanoparticles

A label-free fluorescent method for sensitive detection of humic acid based on poly(thymine)-templated copper nanoparticles is reported.