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A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2 × 104 L mol-1. Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667-240 µmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis. [ABSTRACT FROM AUTHOR]

Amino/hydroxyl-functionalized fluorescent carbon nanodots (C-NanoD) are conveniently synthesized based on hydrothermal carbonization of chitosan at 180 °C. Dialysis membranes with small cut-off masses (500-1000 Da) were found useful for removing the side-products and low molecular mass species to purify the C-NanoD product. Herein, reversed-phase high-performance liquid chromatography (RP-HPLC) has been successfully applied to fractionate the C-NanoD product. The elution order of the C-NanoD species present in the sample follows approximately their core sizes from small to large. The separated C-NanoD fractions are collected and characterized by UV absorption spectroscopy, photoluminescence (PL) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and transmission electron microscopy (TEM). All the C-NanoD fractions display a distinctive absorption band at 300 nm, attributing to the n→π⁎ transition of CO bond. The PL spectra of the fractions display emission peaks at 400-415 nm which are slightly red-shifted with their increase in relative molecular masses. The C-NanoD fractions are fully anatomized by MALDI-TOF MS, displaying their fragmentation mass ion features. The core sizes of some selected C-NanoD are determined as 1.6, 1.8, 2.5, and 3.1 nm by TEM which are in consistent with their HPLC elution order. The findings highlight the virtues of RP-HPLC to fractionate and reveal the unique characteristics of individual C-NanoD species present in an as-synthesized C-NanoD product which may have potential applications in the fields of bioanalysis, bioimaging, catalysis, chemosensing, energy storage, and optoelectronics device. [ABSTRACT FROM AUTHOR]

Glutathione capped silver nanoclusters (GSH@Ag NCs) were prepared by facile sonachemical method in aqueous solution. A new GSH@Ag NCs fluorescent probe for the detection of Fe3+ has been designed based on the significant fluorescence quenching of GSH@Ag NCs. The response to Fe3+ allows for a linear dynamic range from 5 x 10-7 mol/L to 2 x 10-5 mol/L with a detection limit of 1.2 x 10-7 mol/L. The other common metal ions did not cause interference. Moreover, the proposed method was applied to the detection of serum iron contents in human serum samples and the recoveries were 84.12-101.70%. In addition, an interesting fluorescence signal "off-on" phenomena of the Ag NCs probe was observed. The fluorescence of the Ag NCs probe could be switched "off" with addition of Fe3+ solution and "on" in the presence of EDTA solution because of the competition for Fe3+. This property enables the probe to be possible for constructing practicable and reusable sensor. All above features indicated that functionalized silver nanoclusters-based fluorescent probe as sensing platform hold great potential for applications in biological and analytical detection. [ABSTRACT FROM AUTHOR]

The inclusion interaction of the complexes between Vitamin K3 (VK3) and β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutylether-β-cyclodextrin (SBE-β-CD) were studied by using steady-state fluorescence measurements. The various factors affecting the inclusion process were examined in detail. The formation constants and inclusion stoichiometry for VK3–CDs were determined. The results showed that the inclusion ability of β-CD and its derivatives was the order: SBE-β-CD>HP-β-CD>β-CD. The related inclusion mechanism is proposed to explain the inclusion process. A method of determining VK3 was established with the linear range was 2.5×10−6–5.0×10−4 M, and was used to determine the VK3 tablets. The recoveries were in the range of 97.52–103.5%. The results were satisfactory. [Copyright &y& Elsevier]