Contemplation on Detonation Pressures of Nitramines and ­Nitro Aromatics

A physical model and a mathematical theory for the detonation pressures of explosives materials were developed. The pressure values are expressed as function of the detonation velocity (D) and the average mass (m) of the gaseous products, and are applied for various nitramines and aromatic nitro compounds including nitro pyrimidines and nitro triazines. Some regression equations were obtained and discussed. The pressure values show poor linear dependence on the average mass of the products but good dependence on the detonation velocities alone or Dm. Moreover, for the same Dm value nitramines should produce more pressure than aromatic nitro compounds. This work deals with pressure developed by explosion products and interrelates it with detonation pressure within the constraints of certain assumptions and pays attention to so far unnoticed relationships at least under certain circumstances.     

Influence of Methyl Substituent Position on Redox Properties of Nitroaromatics Related to 2,4,6‐Trinitrotoluene

The environmental remediation of military installation sites is very important due to frequently large presence of carcinogenic derivatives of explosives in the ground and in ground waters. These nitroaromatic explosives and their derivatives are assessed by sensing devices. It is highly important to have insight on the reasons affecting the reduction potentials of these compounds. The redox properties of mono‐, di‐ and tri‐nitroaromatic compounds are studied with cyclic voltammetry at a glassy carbon electrode for comparison. We show that the presence of a methyl group in the aromatic system leads into more negative reduction potentials. The ease of nitro group reduction vary from meta>para>ortho positions relative to a methyl group. The redox properties were also studied at various pH ranging from 2 to 10. Acidic environments facilitated the reduction processes at lower potentials. These findings will have a profound influence upon understanding the processes during reductive decontaminations of the polluted sites as well as for construction of highly sensitive sensors for their determination.     

Analysis of nitrophenols in cloud water with a miniaturized light-phase rotary perforator and HPLC-MS

An all-glass miniaturized light-phase rotary perforator for the enrichment of polar compounds has been modified/miniaturized and applied. Its application is demonstrated here for the analysis of nitrophenols and dinitrophenols from low-concentration/low-volume samples. For the method development of high-performance liquid chromatography–mass spectrometry (MS) four eluents were tested: (1) water–methanol, (2) acetic acid–methanol, (3) trifluoroacetic acid–methanol and (4) water–acetonitrile. The last eluent mentioned was used for the subsequent investigation of samples from field experiments. Detection limits varied between 1 ng and 50 pg. The relative standard deviation in repeated measurements was below 15%, corresponding to a good reproducibility. Recoveries ranged between 31 and 100%, showing a significant dependence on the extraction time and the final volume of the sample after evaporation. Quantification was carried out by using deuterated 4-nitrophenol and 2,4-dinitrophenol as standards and applying previously determined response factors. Structure determination of further substances under atmospheric pressure chemical ionization was performed by a first screening with a source collision-induced dissociation, followed by the definite analysis by MS ⁿ . The first results are shown for cloud water, fog water and rainwater samples from different locations.     

Detection and Theoretical Study of Fukui Function of Nitroaromatics by Carbazole-Based Iridium（Ⅲ）Phosphorescent Probe北大核心CSCD

A room temperature phosphorescent Ir（Ⅲ）complex Ir（ppyCz）3 is synthesized by a two-step synthesis method with a carbazole modified organic ligand. The high-efficiency luminescent detection strategy of six familiar nitroaromatics including 1,3-dinitrobenzene,etc. is developed using Ir（ppyCz）3 as the luminescent probe. The highest detection efficiency of 1,3-dinitrobenzene by Ir（ppyCz）3 is demonstrated with the quenching content KSV of（26. 38±1. 05）L/mmol,and minimum detection limit of 2. 50×10−6 mmol/L. Density functional theory calculations and spectral overlap experiments show that the detection mechanism of Ir（ppyCz）3 for the six nitroaromatics is assigned to electron transfer. The sequence of the orbital weighted Fukui function for the six nitroaromatics dovetails with the corresponding detection efficiency sequence of nitroaromatics by Ir（ppyCz）3. © 2022, Science Press (China). All rights reserved.     

Cross-linked poly-vinyl polymers versus polyureas as designed supports for catalytically active M nanoclusters: Part II. Pd/cross-linked poly-vinyl polymers versus Pd/EnCat™30NP in mild hydrogenation reactions

Innovative Pd⁰ heterogeneous catalysts were prepared upon using cross-linked, gel-type, functional acrylic polymers as the supports, along a simple route in use in our laboratories since long. The supports were obtained by polyaddition co-polymerization of N,N-dimethylacrylamide with either 2-acrylamido-2-methylpropane sulfonic acid, methacrylic acid or 4-vinylpyridine, and ethylene glycoldimethacrylate (cross-linker). The performance of these catalysts in the hydrogenation of cyclohexene, trans-methylcinnamate and 4-chloro-2-nitroanisole was compared with that of commercial Pd⁰/EnCat 30NP, produced by Reaxa. One of the catalysts (sulfonic resin as the support) behaved very well as far as activity, stability and selectivity are concerned. These results suggest that heterogeneous metal catalysts supported on polyaddition resins could be developed to become interesting materials for technical applications.     

A fluorescent Cd(II) based 2-D coordination polymer for highly selective detection of nitroaromatics and Hg2+

A 2-D Cd(II) coordination polymer (CP), {[Cd₂(L)₂(4,4′-bipy)₂(H₂O)?7H₂O]_n (1), has been synthesized using 5-aminoisophthalic acid (H₂L) as ligand and 4,4′-bipyridine as co-ligand. A single-crystal X-ray diffraction study shows that 1 is an infinite 2-D layer. CP 1 behaves as a highly selective and sensitive fluorescence chemosensor for detection of Hg²⁺ and 2,4,6-trinitrotoluene (TNT). Furthermore, possible emission quenching in 1 in the presence of nitroaromatics has been addressed with the aid of theoretical calculations. The calculations indicated that there are both electron and energy transfer processes, in addition to electrostatic interaction between 1 and nitroaromatics which contributes to the selective fluorescence quenching.     

Chemosensing of nitroaromatics with a new segmented conjugated quaterphenylene polymer

A new approach for introducing porosity in fluorescent polymer films to increase sensing performance is presented. A novel segmented conjugated polymer composed of p-quaterphenylene segments tethered by their meta positions along the polymer main chain by 2,2-isopropylene spacers was synthesized. The bent nature of its microstructure generates amorphous morphologies that let analytes diffuse rapidly within the films. Fluorescence quenching studies with polymer films and methanol solutions of nitroaromatics showed high sensitivity, fast response and reversibility of the fluorescence quenching. Thus, half of the maximum quench (Q_50%) occurred with nitrobenzene at the micromolar range in less than 1 min in a reversible manner.     

Highly emissive triphenylamine based fluorophores for detection of picric acid

Triphenylamine based, dumbbell shaped, highly fluorescent compound 1 was designed and synthesized. Compound 1 showed blue emission with quantum efficiency as high as 0.78 in benzene solution. Compound 1 showed turn-off sensitivity to picric acid, which is a common constituent of many powerful explosives and unavoidable environmental threats. The turn-off sensitivity to picric acid is attributed to the excited state charge transfer from compound 1 to picric acid. Compound 1 selectively senses picric acid with a detection limit of ∼400 ppb.