N-doped carbon dots as robust fluorescent probes for the rapid detection of hypochlorite.

Great advances have been made in the development of carbon dot (CD)-based fluorescent materials for the detection of hypochlorite in the past few years. However, developing new CDs with high quantum yield (QY) for the rapid detection of hypochlorite and gaining a deeper insight into the detection mechanism still need to be further investigated. Herein, N-doped carbon dots (NCDs) with high QYs, which can reach as high as 67%, were efficiently prepared employing citric acid and o-phenylenediamine as raw materials. Significantly, the NCDs could act as fluorescent probes for the rapid detection of hypochlorite and the limit of detection is calculated to be as low as 12.6 nM on the basis of fluorescent "on-off" effects upon the addition of hypochlorite. Furthermore, UV-vis absorption spectra, Density Functional Theory (DFT) calculations and kinetic analysis of fluorescence (FL) decay were used to investigate the detection mechanism. The results indicate that the electron transfer (ET) process from NCDs to imine-functionalized NCDs (imine-NCDs) and the higher energy gap of imine-NCDs will facilitate the excited-energy of NCDs to be dissipated in the form of a non-radiative decay procedure, resulting in a static quenching mechanism. Therefore, these observations are useful in deepening the understanding of the hypochlorite induced FL quenching mechanism and thereby developing oxidative stress-related detection materials.

Urea-doped carbon dots as fluorescent switches for the selective detection of iodide ions and their mechanistic study.

A facile and green strategy for the fabrication of fluorescent urea-doped carbon dots (N-CDs) has been explored. Significantly, the fluorescent N-CDs could recognize iodide ions (I-) with high selectivity, and their photoluminescence could be efficiently quenched by the addition of I-. The sensitivity analysis for I- indicated a linear relationship in the range from 12.5 to 587 µM with the detection limit as low as 0.47 µM. Furthermore, the I- induced fluorescence (FL) quenching mechanism was investigated employing a combination of techniques, including UV-vis/fluorescence spectroscopy, Density Functional Theory (DFT) calculation, TEM and time-resolved fluorescence decay measurements. The DFT calculation results demonstrated that the amino- and amide groups of N-CDs play a significant role in iodide recognition through the formation of multiple N-H⋯I-, C-H⋯I- and C([double bond, length as m-dash]O)N-H⋯I- interactions with I-. The TEM experiment confirmed the aggregation process when I- was added to the N-CDs solution. Moreover, the radiative decay rate of N-CDs, which was first measured and reported the kinetic behaviors of the FL-quenching process, decreased from 3.30 × 107 s-1 to 1.95 × 107 s-1 after the coordination with I- ions. The reduced lifetime demonstrated that the excited energy dissipation led to a dynamic quenching process. Therefore, such carbon materials can function as effective fluorescent switches for the selective detection of I- ions.

Propane-1,2-diaminium bis-(4-meth-oxy-benzoate).

The asymmetric unit of the title salt, C(3)H(12)N(2) (2+)·2C(8)H(7)O(3) (-), contains two 4-meth-oxy-benzoate anions and one propane-1,2-diaminium cation. All the amino H atoms of the cation are involved in N-H⋯O hydrogen bonds with the carboxyl-ate O atoms of the anions.

(S)-1,2,4-Trimethyl-piperazine-1,4-diium tetra-chloridozincate(II).

In the title compound, (C(7)H(18)N(2))[ZnCl(4)], the Zn atom adopts a slightly distorted tetra-hedral geometry. The diprotonated piperazine ring adopts a chair conformation. In the crystal structure, the cations and anions are linked by inter-molecular N-H⋯Cl hydrogen bonds into a chain along [001].

catena-Poly[(S)-2-methyl-piperazine-1,4-diium [[trichloridobismuthate(III)]-di-µ-chlorido]].

In the crystal structure of the title compound, {(C(5)H(14)N(2))[BiCl(5)]}(n), the Bi(III) cation is coordinated by six Cl(-) anions in a distorted octa-hedral geometry. Two Cl(-) anions bridge neighboring Bi(III) cations, forming a zigzag polymeric chain along the a axis. The discrete methylpiperazinediium cation adopts a normal chair conformation and is linked to the polymeric chains by N-H⋯Cl hydrogen bonding.

Bis(2-amino-benzonitrile)tetra-aqua-cobalt(II) dichloride.

In the crystal structure of the title compound, [Co(C(7)H(6)N(2))(2)(H(2)O)(4)]Cl(2), the Co(II) cation lies on an inversion center and is coordinated by two 2-amino-benzonitrile ligands and four water mol-ecules in a distorted octa-hedral geometry. The Cl(-) counter-anion links with the complex cations via O-H⋯Cl and N-H⋯Cl hydrogen bonding. Inter-molecular O-H⋯N hydrogen bonding links the complex cations, forming supra-molecular chains running along the b axis.

Methyl 1-bromo-2-naphthoate.

In the mol-ecular structure of the title compound, C(12)H(9)BrO(2), the methoxy-carbonyl group is twisted by a dihedral angle of 29.8 (3)°with respect to the naphthalene ring system. An overlapped arrangement is observed between parallel naphthalene ring systems of adjacent mol-ecules, and the face-to-face distance of 3.590 (9) Šsuggests there is π-π stacking in the crystal structure.

3,5-Dichloro-N-(2-methyl-but-3-yn-2-yl)benzamide.

In the title compound, C(12)H(11)Cl(2)NO, the amide group is twisted by a dihedral angle of 31.98 (2)° with respect to the benzene ring. In the crystal structure, mol-ecules are linked via N-H⋯O hydrogen bonds, forming one-dimensional supra-molecular chains.

4-Benzhydryl-1-cinnamylpiperazin-1-ium nitrate.

In the title compound, C(26)H(29)N(2) (+)·NO(3) (-), the dihedral angle formed by the phenyl rings of the benzhydryl group is 66.18 (9)°. Crystal cohesion is enforced by cation-anion C-H⋯O and N-H⋯O hydrogen bonds.