The preparation, characterization, fluorescence (FL) and electrochemiluminescence (ECL) of graphite-like carbon nitride nanoflake particles (g-C(3)N(4) NFPs) and nanoflake films (g-C(3)N(4) NFFs) have been reported. Highly water-dispersible g-C(3)N(4) NFPs with a height of ~5 to 35 nm and a lateral dimension of ~40 to 220 nm have been extracted from bulk g-C(3)N(4) materials by chemical oxidation. New, stable and defined g-C(3)N(4) NFFs can be easily obtained by drying NFPs on certain hydrophilic substrates such as glass or electrode surfaces. Both g-C(3)N(4) NFPs and g-C(3)N(4) NFFs have good FL activities, i.e. they can give strong blue light (435 nm) emission under UV light (365 nm) excitation. The as-prepared g-C(3)N(4) NFFs on a glassy carbon electrode exhibit strong non-surface state ECL activity in the presence of reductive-oxidative coreactants, including dissolved oxygen (O(2)), hydrogen peroxide (H(2)O(2)) and peroxydisulfate (S(2)O(8)(2-)) and give rise to blue light emission (435 nm), which is the same as the wavelength of FL. The non-surface state ECL mechanisms of the g-C(3)N(4) NFF-coreactant systems have been studied and discussed in detail.
A new coreactant electrochemiluminescence (ECL) system including single-layer graphene quantum dots (GQDs) and L-cysteine (L-Cys) was found to be able to produce strong cathodic ECL signal. The ECL signal of GQD/L-Cys coreactant system was revealed to be mainly dependent on some key factors, including the oxidation of L-Cys, the presence of dissolved oxygen and the reduction of GQDs. Then, a possible ECL mechanism was proposed for the coreactant ECL system. Furthermore, the ECL signal of the GQD/L-Cys system was observed to be quenched by lead(II) ions (Pb(2+)). After optimization of some important experimental conditions, including concentrations of GQDs and L-Cys, potential scan rate, response time, and pH value, an ECL sensor was developed for the detection of Pb(2+). The new methodology can offer a rapid, reliable, and selective detection of Pb(2+) with a detection limit of 70 nM and a dynamic range from 100 nM to 10 μM.
Electrochemiluminescence of the luminol-O(2) system in an electrolyte-free N,N-dimethylformamide (DMF)-dipropylamine (DPA) cosolution is induced by the formation of a carbamate ionic liquid (IL) from the reaction between CO(2) and DPA, on the basis of which a facile ECL sensor for measuring atmospheric CO(2) has been developed. This ECL sensing method shows several advantages in the detection of CO(2), such as high safety, high selectivity, wide linear response range, and good sensitivity. The gas sensor was found to have a linear response range from 100 ppm to 100 v/v% and a detection limit of 80 ppm (at signal-to-noise ratio of 3). This is the first reported IL-induced ECL sensor for a gas, thus the principle of this type of sensor and the IL-induced ECL mechanism have been demonstrated in detail.
This work reports that ammonia (NH(3)) can be used as an efficient co-reactant for tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) in ionic liquids (ILs), on the basis of which a signal-on ECL sensor for directly detecting gaseous NH(3) has been developed. The NH(3) ECL sensor has a very high sensitivity, with a detection limit of 10 ppt NH(3) (at signal-to-noise ratio of 3) without any preconcentration. The high sensitivity is mainly due to the zero ECL background of Ru(bpy)(3)(2+) in the ILs, strong co-reactant ECL activity of NH(3), and high solubility of NH(3) in imidazolium-based ILs. Additionally, the ECL sensor shows an excellent selectivity against common interfering gases and a wide linear response range from 10 ppt to 10 ppm.
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