Başoğlu, Aysel; Ocak, Ümmühan; Iyidoğan, Ayşegül Karaküçük

A new simple spectrophotometric method for the determination of Cu2+ ion was developed using an thiosemicarbazone compound, 2-{4-[Bis(2-chloroethyl)amino]benzylidene}-N-[(4-methylthio)phenyl]hydrazinecarbothioamide (TSC). A simultaneous color change was observed (from colorless to bright yellow) by the addition of Cu2+ ion to the TSC ligand solution. The maximum absorbance of the TSC ligand measured at 366 nm was decreased by the presence of Cu2+ ion. The graphs of absorbance obtained by means of the Job’s method and the molar-ratio method proposed a complex formation with a 1:2 Cu2+–TSC ligand stoichiometry. The molar-ratio method with emission measurements also confirmed the stoichiometry. The complex stability constant of TSC–Cu2+ complex (K) was evaluated to be 1.76 × 105. The proposed spectrophotometric method was associated with the change in absorbance at 366 nm owing to the interaction between the TSC ligand and Cu2+ ion. From the spectrophotometric titration data, it was pointed out that TSC ligand (1.5 × 10− 5 mol L-1) selectively reacted with Cu2+ ion in DMSO/water (1:1, v/v, citrate buffer at pH = 6.0). The calibration curve for Cu2+ ion was obtained with a good linearity in the range of 0.0191–0.3241 mg L-1. The detection limit for Cu2+ ion was 0.0063 mg L-1. The proposed method was achievemently implemented in real water samples (drink water, tap water and, distilled water). Satisfactory recoveries were confirmed at three different concentrations. The method presented a relative standard deviation (RSD%) of less than 3.08%.

Başoğlu, Aysel; Ocak, Ümmühan; Gümrükçüoğlu, Abidin

A simple method for the green synthesis of fluorescent carbon quantum dots (CQDs) has been developed by using roasted chickpea as carbon source in one-step without using any chemical. Interestingly, not only the carbon source of CQDs and the whole synthesis procedure are environmentally friendly, but also the synthesized CQDs have shown many advantageous properties such as high fluorescence intensity, excellent photostability, and good water solubility. CQDs which were firstly synthesized from roasted–chickpeas by a microwave-assisted pyrolysis have been characterized using UV-vis absorption spectroscopy, fluorescence spectroscopy, fourier transform infrared spectroscopy (FTIR) spectroscopy, X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). In addition, the details of the structure have been revealed by the electron diffraction (SAED; selected-area electron diffraction) method based on the TEM images. The synthesized CQDs emits blue fluorescence under UV light (at 365 nm). A microwave oven (350 watts) was used to prepare CQDs in 120 s. The effect of various metal ions on the fluorescence intensity of CQDs was investigated in order to determine its utality in the detection of metal ions. It was determined that 1.38 mg/L of Fe3+ ions quenched the fluorescence intensity of the CQDs by 65%. The linear range is observed between 11.25 and 37.50 μM with limit of detection (LOD) and limit of quantification (LOQ) of 2.74 μM and 8.22 μM, respectively. CQDs which are highly selective and sensitive for Fe3+ ions was used to determine Fe3+ ions in certified reference material (CRM-SA-C). Fe3+ ions concentration was determined with precision values of more than 95% as intra-day and inter-day relative standard deviation (RSD%) is 5 at room temperature.