Density functional theory investigation of CN on Cu(1 1 1), Ni(1 1 1) and Ni(1 0 0)

The adsorption of CN on Cu(1 1 1), Ni(1 1 1) and Ni(1 0 0) has been investigated using density functional theory (DFT). While experimental studies of CN on Cu(1 1 1) show the molecular axis to be essentially parallel to the surface, the normally-preferred DFT approach using the generalised gradient approximation (GGA) yields a lowest energy configuration with the C-N axis perpendicular to the surface, although calculations using the local density approximation (LDA) do indicate that the experimental geometry is energetically favoured. The same conclusions are found for CN on Ni(1 1 1); on both surfaces bonding through the N atom is always unfavourable, in contrast to some earlier published results of ab initio calculations for Ni(1 1 1)/CN and Ni(1 0 0)/CN. The different predictions of the GGA and LDA approaches may lie in subtly different relative energies of the CN 5σ and 1π orbitals, a situation somewhat similar to that for CO adsorbed on Pt(1 1 1) which has proved challenging for DFT calculations. On Ni(1 0 0) GGA calculations favour a lying-down species in a hollow site in a geometry rather similar to that found experimentally and in GGA calculations for CN on Ni(1 1 0).     

Cyclic Voltammetric Study of the Oxidation of Catechols in the Presence of Cyanide Ion

Electrochemical oxidation of catechols has been studied in the presence of cyanide ion as nucleophile in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate that the participation of catechols in the Michael reaction with cyanide ion to form the corresponding o‐dihydroxybenzonitrile. Based on an EC mechanism, the homogeneous rate constants were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results.     

H2 + CN(n=0,1)→H + HCN振动选态反应

用从头算方法获得了Ｈ２＋ＣＮ反应的内禀反应坐标（ＩＲＣ），沿着ＩＲＣ，计算了各垂直于ＩＲＣ的简正模所对应的频率（Ｗ）以及沿ＩＲＣ运动与垂直ＩＲＣ运动的简正模之间的耦合常数（ＢＫＦ），根据传统过渡态，变分过渡态理论和选态公式，计算了ｎＣＮ＝０及ｎＣＮ＝１时反应的速率常数，并得到了实验相一致的结果，还计算了ｎＣＨ＝１及ｎＣＮ＝１的Ｈ＋ＨＣＮ→Ｈ２＋ＣＮ反应速率常数，可供实验工作者参考。     

A Novel 3‐D Heterobimetallic Cyano‐bridged Coordination Polymer Incorporating Ag···Ag Interaction: [Cu(dien)Ag(CN)2]2[Ag2(CN)3][Ag(CN)2]

A three‐dimensional cyano‐bridged copper(II) complex, [Cu(dien)Ag(CN)₂]₂[Ag₂(CN)₃][Ag(CN)₂] ( 1 ) (dien = diethylenetriamine), has been prepared and characterized by X‐ray crystallography. Complex 1 crystallized in the monoclinic space group P2₁/n with a = 6.988(2), b = 17.615(6), c = 12.564(4) Å, β = 90.790(5)°. The crystal consists of cis‐[Cu(dien)]²⁺ units bridged by [Ag(CN)₂]^— to form a zig‐zag chain. The Ag atoms of the free and bridging [Ag(CN)₂]^— link together to form additional infinite zig‐zag chains with short Ag···Ag distances. The presence of Ag···Ag interactions effectively increases the dimensionality from a 1‐D chain to a 3‐D coordination polymer.     

Fast and highly selective determination of cyanide with 2,2-dihydroxy-1,3-indanedione

A very simple, accurate, fast, selective and sensitive assay of cyanide based on its reaction with 2,2-dihydroxy-l,3-indanedione at basic pH is proposed. As little as 0.01 μg ml⁻¹ of cyanide can be determined. The molar absorptivity may reach 5.1–8.0×10⁴ l mol⁻¹ cm⁻¹ depending on the reaction conditions. Thus, 1 ml of sample solution is mixed with 500 μl of 5 mg ml⁻¹ solution of 2,2-dihydroxy-1,3-indanedione monohydrate in 2% sodium carbonate. The absorbance of the purple color is measured at 510 nm in 1-cm glass cuvettes, 10–15 min after mixing the reagents. The procedure could also be used to identify free CN⁻ in natural waters and hydrocyanic acid in the environment.     

A selective modified carbon paste electrode for determination of cyanide using tetra-3,4-pyridinoporphyrazinatocobalt(II)

A chemically modified carbon paste electrode with 3,4-tetra pyridinoporphirazinatocobalt(II) (Co(3,4 tppa) was applied to the determination of free cyanide ion. The electrode has a linear range between 1.5 × 10⁻⁵ M and 1.0 × 10⁻² M with a Nernstian slope of 60 ± 1.5 mV/decade and its detection limit is 9 × 10⁻⁶ M. The response time of electrode is 5 min. The proposed electrode was applied successfully for the determination of cyanide in commercially available spring water. Some anions, such as SCN⁻, I⁻, Cl⁻, Br⁻ and oxalate that are usually serious interfering species for most of cyanide selective electrodes, did not have any interfering effect for this proposed electrode.     

Surface-modified CdSe quantum dots as luminescent probes for cyanide determination

Luminescent surface-modified CdSe semiconductor quantum dots (QDs), with nanoparticle (NP) size distribution in the order of 2-7 nm, have been synthesized for optical determination of cyanide ions. The nanoparticles have been functionalised with tert-butyl-N-(2-mercaptoethyl)-carbamate (BMC) groups and exhibit a strong fluorescent emission at about 580 nm with rather long fluorescence lifetimes (several hundred nanoseconds) in aerated methanolic solution. The observed luminescence emitted by the synthesized nanocrystals was tremendously increased by photo-activation under sunlight exposure. The functionalised QDs turned out to exhibit excellent long-term stability when stored in the dark (no significant changes in QDs luminescence emission intensity was observed even after two months from synthesis). The functionalisation of the NPs with carbamate ligand allowed a highly sensitive determination of free cyanide via analyte-induced changes in the photoluminescence (fluorescence quenching of intensity at 580 nm and lifetime changes) of the modified quantum dots (excited at 400 nm). A detection limit of 1.1 × 10⁻⁷ M (2.9 μg l⁻¹) of cyanide ions was obtained, while the interfering effect of other inorganic anions (including NO₃⁻, Cl⁻ or SCN⁻) was negligible even at 200-fold level concentrations in excess of cyanide.     

Simultaneous kinetic spectrophotometric determination of cyanide and thiocyanate using the partial least squares (PLS) regression

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN⁻ and SCN⁻ ions is described. The method is based on the difference in the rate of the reaction between CN⁻ and SCN⁻ ions with chloramine-T in a pH 4.0 buffer solution and at 30 °C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578 nm in the time range 20-180 s after initiation of the reaction with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0 ng mL⁻¹ for CN⁻ and SCN⁻ ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples.