ZnS nanoparticles for high-sensitive fluorescent detection of pyridine compounds
Graphical abstract
Highlights
► The synthesis of ZnS nanoparticles (NPs) is simple and low cost. ► The nanoparticles are water-soluble, which could expand their applying areas. ► The fluorescence intensity of ZnS NPs can be quenched by pyridine compounds. ► ZnS NPs can act as a novel fluorescent sensor for pyridine compounds. ► The sensor exhibits high sensitivity, fast response and low detection limit.
Introduction
Nowadays, nanostructure materials are not only at the very frontier of fundamental materials research, but they have also entered into people’s daily life step by step [1], [2], [3]. With the deteriorating trend of environmental pollution and the rising awareness of the public vulnerability to the chemical and biological threats, the detection techniques with both high sensitivity and reliability are demanded urgently. The application of nanostructure materials to the design of chemical sensors has attracted considerable attention due to their tremendous specific surface, high activity, excellent anti-photobleaching and tunable emission [4], [5], [6]. As a developing semiconductor material star, ZnS nanoparticles (NPs) are low toxicity materials with a wide band gap [7] of ∼3.72 eV (cubic zinc blende structure) and ∼3.78 eV (hexagonal wurtzite structure), exhibiting remarkable optical and electrical properties [8], [9], [10], [11], which suggest that they may be particularly well-suited for the manufacture of novel sensor. At present, ZnS NPs can be used to detect the DNA molecular [12], [13], protein [14], organic molecule [15], [16], [17], pH value [18], [19], metal ion [20], [21], [22], [23], etc.
Pyridine and its derivatives are important chemical raw materials, which are mainly used as solvent and intermediate in the production of agricultural chemicals, dyestuffs, additives, drugs, and others. However, this foul-smelling and toxic substance could intrude into the human living environment through the discharge of various industrial effluents and exhaust gases. Besides, pyridine and its derivatives are frequently found in the cigarette smoke [24], and also generated during the putrefaction processes of certain foodstuffs [25]. If inhaled, ingested or absorbed through skin, these chemicals can cause many potentially harmful effects on human body, which include nausea, vomiting, headaches, coughing, asthmatic breathing, laryngitis and even cancers [26]. Consequently, the detection of pyridine has become a heightened need for the health of human and the development of environment-friendly society. Various approaches have been established for the detection of pyridine, such as barbituric acid spectrophotometry [27], high-performance liquid chromatography [28], [29], gas chromatography [30], [31], [32], liquid chromatography–mass spectrometry (LC–MS) [24], gas chromatography–mass spectrometry (GC–MS) [33], [34], optical fiber sensing method [35], but the method based on the fluorescent of nanomaterials has not been reported so far.
Herein, we report a very simple method for the synthesis of TGO-capped ZnS NPs with a narrow size distribution and good optical properties. Compared with other traditional methods, the preparation is a one-step approach using non-toxic and low cost raw materials, and the obtained nanoparticles are water-soluble, which could expand their applying areas particularly in chemical and biological fields. When the pyridine is added to TGO-capped ZnS NPs aqueous solution, it could attach to the surface of ZnS NPs, and result in a significant fluorescence quenching. Based on this phenomenon, a novel fluorescent sensor for the determination of pyridine compounds is proposed, and the performance of this ZnS NPs sensor exhibits high sensitivity, simple, fast and low detection limit. The possible mechanism of fluorescence quenching is also discussed.
Section snippets
Experimental
The TGO-capped ZnS NPs were synthesized by chemical precipitation method as follows: 1.00 g Zn (CH3COO)2·2H2O (Tianjin Bodi Chemical Holding Co., Ltd.) and 1.20 g alpha-thioglycerol (TGO, Shanghai TCI Development Co., Ltd.) were dissolved in 285 mL secondary distilled water (homemade). The TGO acts as a capping agent to prevent the agglomeration of particles and stabilize the ZnS NPs. The pH value of the mixed solution was adjusted to 11.20 by 2 M NaOH solution. After about 30 min of bubbling
Results and discussion
FT-IR spectra of TGO and TGO-capped ZnS NPs are shown in Fig. 1. A broad absorption band in the 3000–3696 cm−1region is associated with the stretching vibrations of hydroxyl groups in bound water and TGO. The peaks at 2930 and 2879 cm−1 are assigned to the stretching vibrations of C–H groups of TGO on the surface of ZnS NPs. The deformation vibrations of the methine and methylene groups in TGO located at 1633 and 1417 cm−1 are also found. The characteristic vibrations at 1064 and 1035 cm−1 belong
Conclusions
In summary, water-soluble ZnS NPs were successfully fabricated through a simple chemical precipitation method. Formation of TGO-capped ZnS NPs was confirmed by FT-IR measurement. TGO-capped ZnS NPs exhibited the cubic zinc blende structure with an average diameter of ∼2.94 nm. The band-gap energy of TGO-capped ZnS NPs was estimated to be 4.40 eV, showing the influence of strong quantum confinement. The fluorescence properties of TGO-capped ZnS NPs were investigated in depth, the peaks located at
Acknowledgments
This work was supported by the Key Technologies R&D Program for the 12th Five-Year Plan (2012BAJ24B04-3) of the Ministry of Science and Technology of the Peoples Republic of China and by the Fundamental Research Funds for the Central Universities, China.
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