Effect of background electrolytes on the adsorption of nitroaromatic compounds onto bentonite

To further elucidate interaction of nitroaromatic compounds with mineral surface, the sorption of m-dinitrobenzene （m-DNB） and nitrobenzene to original bentonite in aqueous solution containing different electrolytes （i.e., KCl, NH4Cl, CaCl2 and Tetramethylammonium bromide （TMAB）） was studied. The sorption of m-DNB was greatly enhanced with the presence of KCl and NH4Cl, while little influence was observed with CaCl2 and TMAB, following the order of KCl 〉 NH4Cl 〉〉 TMAB, CaCl2, or DI water. For nitrobenzene, sorption enhancement only occurred at high nitrobenzene concentrations in the presence of KCl, and the solute equilibrium concentration at inflexion point was lowered with increasing KCl concentration. These sorption enhancements were significantly promoted with the increase of electrolyte concentration. The salting-out effect is insufficient to account for the sorption enhancement by original bentonite with increasing KCI or NH4Cl concentration. X-ray diffraction patterns of bentonite suspensions indicated that the sorption enhancement of m-DNB was attributed to the intercalation of K^＋ or NH4^＋ into bentonite interlayer and then dehydration with m-DNB to form inner-sphere complexes, which caused previously expanded bentonite interlayers to collapse in aqueous suspension, thus further enhanced the interaction of phenyl with siloxane surface. In comparison, the sorption enhancement of NB is attributed to the formation of outer-sphere complexes with K^＋ at high solute-loadings （〉 20（0-400 mg/kg）. The sorption of m-DNB to initially modified TMA^＋-bentonite and K^＋-bentonite was almost the same as respective sorption to original bentonite in solution containing TMA^＋ and K^＋.

Structural Characterization and Acute Toxicity Simulation for Nitroaromatic Compounds

The three-dimensional holographic vector of atomic interaction field（3D-Ho VAIF） is used to characterize the molecular structures of 45 nitroaromatic compounds.Two quantitative structure-toxicity relationship（QSAR） models are built up by stepwise regression（SMR）,multiple linear regression（MLR） and partial least-squares regression（PLS）.The correlation coefficients（R） of the models are 0.960 and 0.961,respectively.Then the models are evaluated by performing the cross-validation with the leave-one-out（LOO） procedure and the correlation coefficients（RCV） are 0.949 and 0.941,respectively.The results show that the descriptors can successfully describe the structures of organic compounds.The stability and predictability of the model are satisfactory.

QSPR of Thermal Stability of Nitroaromatic Explosives Using Theoretical Descriptors Derived from Electrostatic Potentials on the Molecular Surface

In the present study,geometrical optimization and electrostatic potential calcula-tions have been performed for 22 nitroaromatic compounds at the HF/6-31G level of theory.A number of statistically based parameters have been obtained.Linear relationship between the decomposition enthalpy（taken as a macroscopic property related to explosibility） of nitroaromatic compounds and the structural descriptors have been established by multiple regression method.The result shows that the quantities derived from electrostatic potentialsΣ V sind＋,,Vsind- and Vs,max can be well used to express the quantitative structure-decomposition enthalpy relationship of nitroa-romatic compounds,which proves the general applicability of this parameter set to a great extent.Good predictive capabilities have also been demonstrated.

Magnetic graphene oxide-anchored Ni/Cu nanoparticles with a Cu-rich surface for transfer hydrogenation of nitroaromatics

The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell(Ni/Cu NPs)were successfully synthesized by a liquid-phase thermal decomposition method.The content of copper and nickel in Ni/Cu NPs was controllable by adjusting the ratio of two metal precursors,copper formate(Cuf)and nickel acetate tetrahydrate(Ni(OAc)_(2)·4H_(2)O).Ni/Cu NPs were further anchored on graphene oxide(GO)to prepare a magnetic composite catalyst,called Ni/Cu-GO.The dispersibility of Ni/Cu NPs in solution was enhanced by GO anchoring to prevent the sintering and aggregation during the reaction process,thereby ensuring the catalytic and cycling performance of the catalyst.The catalytic transfer hydrogenation(CTH)reaction of nitroaromatics was investigated when ammonia borane was used as the hydrogen source.Cu dominated the main catalytic role in the reaction,while Ni played a synergistic role of catalysis and providing magnetic properties for separation.The Ni_(7)/Cu_(3)-GO catalyst exhibited the best catalytic performance with the conversion and yield of 99%and 96%,respectively,when 2-methyl-5-nitrophenol was used as the substrate.The Ni_(7)/Cu_(3)-GO catalyst also exhibited excellent cyclic catalytic performance with the 5-amino-2-methylphenol yield of above 90%after six cycles.In addition,the Ni_(7)/Cu_(3)-GO catalyst could be quickly recycled by magnetic separation.Moreover,the Ni_(7)/Cu_(3)-GO catalyst showed good catalytic performance for halogen-containing nitroaromatics without dehalogenation.

Reductive Metabolism of Nitroaromatic Compounds by Various Liver Microsomes

Nitroaromatic compounds were reductively metabolized to the corresponding amine compounds via the intermediate hydroxylamines by liver microsomes from pig,rat,chook,cattle,sheep,paralichthys olivaceus and cyprinoid in varied reactivity.Similar with baker＇s yeast,the pig,rat and sheep liver microsomes exhibited high reactivity toward 4-nitro-1,2-dicyanbenzen（1a）,while the cyprinoid liver microsomes were inefficient.Contrasted to compound 1a,monocyannitrobenzene（2a） was difficult to reduce by pig liver microsomes.In opposition to grape cells,pig liver microsomes exhibited activities toward some aromatic hydroxylamine compounds.

Effect of monotoxicity and mixtoxicity of nitroaromatics to the green algae, Scienedesmus obliquus

In general, many pollutants co\|exist in natural aquatic ecosystems. They affect each other and occur different results, such as synergism, addition and antagonism. So the research at mixtoxicity of contaminants to aquatic organism is more important than monotoxicity. In this paper, 50% effectual inhibition concentration 48h \%EC\%\-\{50\} values of 6 kinds of nitroaromatic compounds to the green algae, \%Scenedesmus obliquus,\% were investigated. Mixtoxic experiments, in which any combination of 2,4\|DNT and other 6 kinds of compounds, indicate: (1) synergisms between 2,4\|DNT and 4\|NAn, as well as 4\|NAnis, 1,4\|DNB; (2) antagonisms between 2,4\|DNT and 4\|NT, as well as 4\|NPh, 4\|NCB.

Linear and Nonlinear QSPR Models for Predicting Thermal Stabilities of Nitroaromatic Compounds

Quantitative structure-property relationships（QSPRs） have been developed to predict the thermal stability for a set of 22 nitroaromatic compounds by means of the theoretical descriptors derived from electrostatic potentials on molecular surface. Several techniques, including partial least squares regression（PLS）, least-squares support vector machine（LSSVM） and Gaussian process（GP） have been utilized to establish the relationships between the structural descriptor and the decomposition enthalpy. The nonlinear LSSVM and GP models have proven to own a better predictive ability than the linear PLS method. Moreover, owing to its ability to handle both linear- and nonlinear-hybrid relationship, GP gives a stronger fitting ability and a better predictive power than LSSVM, and therefore could be well applied to developing QSPR models for the thermal stability of nitroaromatic explosives.

Tough lanthanide luminescent hydrogel for nitroaromatics detection

Luminescent hydrogels have received considerable attention in the application of sensors.Nitroaro matics are harmful to human health and can be carcinogenic.Some skin allergies and central nervous system injuries may also be attributed to the over exposure to nitroaromatics.Thus,nitroaromatics sensor with fast detection and low detection limit is highly desirable.Herein,novel tough hydrogels were prepared by introducing hydrogen bonds and covalent bonds into the interpenetrating networks of modified chitosan and poly(vinyl alcohol)(PVA) via frozen-thawing induced chemical cross-linking.The synthesized hydrogels exhibit high mechanical strength(0.23 MPa tensile strength at 140% tensile strain,1.0 MPa compressive strength at 80% compressive strain).Strong green emission was realized by energy transfer from the modified chitosan to Tb^(3+)via the so-called "antenna effect." The prepared luminescent hydrogels show an excellent detection effect on nitroaromatic compounds and its detection limit can reach ppm-level.The hydrogels also exhibit good reversibility and a fast "off-on" fluorescence switching process.This work may open up a new way for the development of stable,rapid,and reusable sensors for the detection of harmful nitroaromatics.

Nanostructured Ni-MoCx:An efficient non-noble metal catalyst for the chemoselective hydrogenation of nitroaromatics

Catalysts for chemoselective hydrogenation are of vital importance for the synthesis of various important chemicals and intermediates.Herein we developed a simple method for preparing a highly efficient Ni-MoC_(x)nanocomposite catalyst via temperature-programmed carburization of a polyoxometalate precursor.X-ray diffraction(XRD),scanning transmission electron microscopy(STEM),X-ray photoelectron spectroscopy(XPS),and X-ray absorption spectroscopy(XAS)analyses indicate that the resulting mesoporous nanocomposite catalyst is made up of well-dispersed metallic nickel particles embedded in a MoC_(x)matrix.This catalyst exhibits high activity and selectivity(>99%)in the hydrogenation of various substituted nitroaromatics to corresponding anilines.The high efficiency is attributed to the intimate contact of the constituents favoring electron transfer and hydrogen adsorption.Dihydrogen is physisorbed on the carbide support and dissociates on the nickel particles,as evidenced by Mo K-edge X-ray absorption near-edge structure(XANES)spectra,density functional theory(DFT),and hydrogen-deuterium exchange.The remarkable catalytic performance of the catalyst could be traced back to the synergistic interaction between the Ni particles and the carbide support.In-situ infrared spectroscopy and DFT simulations indicated that the adsorption/activation of the nitro group is favored compared to that of other substituents at the aromatic ring.In recyclability tests,the Ni-MoC_(x)nanocomposite showed no significant loss of catalytic performance in seven consecutive runs,indicating its robust nature.

Rational design of an AIE-active metal-organic framework for highly sensitive and portable sensing nitroaromatic explosives

Herein,we report a new metal-organic framework with an AIE ligand (H_(4)TCPP=2,3,5,6-tetra-(4-carboxyphenyl)pyrazine) and Mg^(2+) ions,that is,[Mg_(2)(H_(2)O)_(4)TCPP]·DMF·5CH_(3)CN (Mg-TCPP,TCPP=tetra-(4-carboxyphenyl)pyrazine) for detection of nitroaromatic explosives.Due to the coordination effect and restricted intramolecular rotation,Mg-TCPP exhibits bright blue light.As a fluorescent sensor,Mg-TCPP exhibits high selectivity and sensitivity for sensing 2,4,6-trinitrophenol (TNP) by quenching behaviors with the Stern-Volmer quenching constant (K_(SV)) of 3.63×10^(5)L/mol and achieves the low limit of detection of 25.6 ppb,which is beyond most of the previously reported fluorescent materials.Notably,the portable Mg-TCPP films are prepared and it can be used for rapid and sensitive TNP detection in a variety of environments including organic solvent and aqueous solution.Moreover,TNP vapor can be detected within 3 min by naked eye and the film could be regenerated under simple solvent cleaning.

2D/3D-QSAR comparative study on mutagenicity of nitroaromatics

Nitroaromatics are typical toxic organic pollutants and are ubiquitous in environment with diverse structures. They are widely used in many industries and formed during many natural and anthropogenic processes. Most of these pollutants are potentially carcinogenic and the as-sessment and prediction of the mutagenicity of nitroaromatics are of great interest. In this paper the structure-mutagenicity relationships of 219 nitroaromatics are investigated by molecular or-bital theory based classic structure-activity relationships and comparative molecular field analysis (CoMFA). A comparison is undertaken in respect of the interpretation of mechanism and predic-tive ability for these two categories of QSAR approaches and highly predictive QSAR models have been developed.

General Reductive Amination of Aldehydes and Ketones with Amines and Nitroaromatics under H2 by Recyclable Iridium Catalysts

Heterogeneous iridium catalysts were prepared and applied for the reductive amination of aldehydes and ketones with nitroaromatics and amines using H2. The iridium catalysts were prepared by pyrolysis of ionic liquid 1-methyl-3-cyanomethylimidazoulium chloride （[MCNI]C1） with iridium chloride （IrC13） in activated carbons. Iridium particles were well dispersed and stable in the N-doped carbon materials from [MCNI]C1 with activated carbon. The Ir@NC（600-2h） catalyst was found to be highly active and selective for the reductive amination of aldehydes and ketones using H2 and a variety of nitrobenzenes and amines were selectively converted into the corresponding secondary and tertiary amines. The Ir@NC（600-2h） catalyst can be reusable several times without evident deactivation.

DFT Study on the QSAR of Nitroaromatic Compound Toxicity to the Fathead Minnow

The DFT-B3LYP method, with the basis set 6-311G, was employed to calculate the molecular geometries and electronic structures of 31 nitroaromatics. EHOMO, ELUMO, QC, QN. QNO2 and μ were selected as quantum chemical descriptors. The acute toxicity （-lg LC50） of these compounds to the fathead minnow along with the six descriptors was used to establish the quantitative structure-activity relationships （QSARs）, Through stepwise multiple linear regression analysis, a model was established as follows： -lg LC50=9.524-39.527ELUMO＋16.859EHOMO＋15.130QNO2＋4.166QC （n=28, R=0.912, SE=0.361, F=28.468）. The model was applied to predict and elucidate the toxicity of nitroaromatics successfully. Furthermore, a metabolic route of nitroaromatics in fathead minnow was proposed.

Ligand controlled structure of cadmium(Ⅱ) metal-organic frameworks for fluorescence sensing of Fe^(3+) ion and nitroaromatic compounds

Three cadmium(II) metal-organic frameworks(MOFs) based on tetracarboxylate ligands, namely[Cd_2(TTTA)(DMF)_3]·2 DMF(1),[Cd_2(TB)(H_2O)_4]·3DMF·H_2O(2)and [Cd(TEB)_(0.5)].2 DMF.4 H_2O(3) have been designed and synthesized. Complex 1 is a 2-dimensional(2 D) 3,4-connected network with 3,4 L13 topology, complex 2 features a 3-dimensional(3D) 3,4-connected tfa topology with a 2-fold interpenetrating structure and complex 3 has a 3D 4-connected dia topology with a 4-fold interpenetrating structure. Interestingly, 2 exhibits permanent pores and selective adsorption of CO_2 over CH_4. In addition, 2 shows fluorescence sensing of Fe^(3+) ion and rapid detection of nitroaromatic compounds(NACs) through fluorescence quenching.

Development of a homogenous assay based on fluorescent imprinted nanoparticles for analysis of nitroaromatic compounds

Herein we describe the development of a homogeneous assay for the detection of 4-nitroaniline(4-NA)and 2,4-dinitroaniline(2,4-diNA).Thisassay relies on fluorescent molecularly imprinted nanoparticles(nano MIPs)which,upon interaction with the target analytes,generate areduction in fluorescence emission intensity(quenching).This is due to a resp on sive fluorescent monomer(N-2-propenyl-(5-dimethylamino)-1-naphthalene sulphonamide)employed in the manufacture of the nanoMIPs which,by virtue of the imprinting process,is capable of selectiveinteraction with the target an alyte,thus giving rise to a quenching effect.Selectivity experiments showed excellent recognition propertiestoward the target molecule.Under optimal conditions,the fluorescence intensity of these nano MIPs decreased as the concentration of theimprinted analyte increased from 10 nM to 2.71 pM.A linear relation between the negative logarithm of 4-NA or 2,4-diNA concentrations and the fluorescence intensity for both nanosystems was found(R^2=0.991 and R^2=0.9895),with excellent sensitivity(limit of detection(LOD)=7 and 6 nM,respectively).Furthermore,both nanosystems have been successfully applied for detection of 4-NA or 2,4-diNA in tap water,withrecoveries between 90%to 100.6%and 92%to 100.3%,respectively.Thanks to the versatility of the imprinting process,this nanosystemholds the potential for further development of several optical sensors for many other compounds.

Two alkynyl functionalized Co（Ⅱ）-MOFs as fluorescent sensors exhibiting selectivity and sensitivity for Fe3+ and nitroaromatic compounds

Two Co(II)-MOFs with different structures were successfully synthesized under the premise of designing two ligands containing alkynyl functional groups. Complexes 1 ([Co(TEPA)(TPT)2/3]·2DMF·H2O) and 2 ([Co(EPA)(TPT)]·1.5DMF·1.5H2O) show excellent luminescence properties. Meanwhile, as fluorescent sensors, complexes 1 and 2 exhibit selectivity and sensitivity for Fe3+ with the Ksv of 1.520 ×104 L/mol and 3.543 ×104 L/mol, which can rapidly detect nitroaromatic compounds in methanol and ethanol, especially for 2,4-NPH through fluorescence quenching with high quenching efficiency. In particular, the Ksv value of complexes 1 and 2 towards 2,4-NPH can reach up to 1.627 ×105 L/mol and 9.600 ×104 L/mol, demonstrating that complexes 1 and 2 are good candidates for the identification and detection of Fe3+and nitroaromatic compounds.

3-D QSAR study on a set of nitroaromatic compounds

The 3-D relationships between the structures of 25 nitroaromatic compounds and their toxicities have been investigated using the comparative molecular field analysis (CoMFA) method, and a 3-D QSAR model with considerable prediction ability is obtained. In comparison with traditional 2-D techniques, CoMFA helps to give a better interpretation of toxic mechanism of tested compounds.

Robust and easily retrievable Pd/Ti3C2Tx■graphene hydrogels for efficient catalytic hydrogenation of nitroaromatic compounds

Ti3C2Tx has been emerging as an attractive platform to prepare composite catalysts,and their assembly into integrated catalytic mate rials repre sents a key step forward toward practical applications.Howeve r,the swelling behavior of Ti3C2Tx leads to significant structure change,which challenges the stability of Ti3C2Tx-based integrated functional materials for catalytic applications.Here we report a facile synthesis of Pd/Ti3C2Tx■graphene hydrogels in which Pd/Ti3C2Tx are spatially encapsulated in the 3 D porous graphene framework.The porous interconnected structure not only affords efficient mass transfer and desirable functional accessibility to catalytic active sites,but also effectively buffers the swelling behavior of Ti3C2Tx.When applied for catalytic hydrogenation of nitroaromatic compounds,the mechanically robust Pd/Ti3C2Tx■graphene hydrogels exhibit efficient activities,easy separability,and good cyclability.This work is expected to promote the application of Ti3C2Tx-based functional materials for practical applications involving interactions with salt solutions,such as supercapacitors,catalysis,and water purification.

Non-contact biomimetic mechanism for selective hydrogenation of nitroaromatics on heterogeneous metal nanocatalysts

While the enzymatic reduction of unsaturated compounds usually has high specificity,highly selective reduction processes are hardly realized by heterogeneous industrial catalysts,which is critical for the green production of many fine chemicals.Here,we report an unexpected discovery of a biomimetic behavior of dicyandiamide(DICY)-modified Pt nanocatalysts for the green hydrogenation of a wide range of nitroaromatics.We demonstrate that the surface modification by DICY not only prevents the direct contact of nitroaromatic reactants with Pt surface but also induces an effective non-contact hydrogenation mechanism mediated by protons and electrons.In such a process,the DICY layer serves as a“semi-permeable membrane”to allow the permeation of H_(2) molecules for being activated into electrons and protons at the Pt-DICY interface.With the generation of separated protons and electrons,the nitro group with strong electrophilic properties can be hydrogenated through the electron transfer followed by the proton transfer,which is facilitated by the hydrogen bonding network formed by protonated DICY.The unique mechanism makes it highly directional toward the hydrogenation of nitro groups without side reactions.Owing to its capability to largely eliminate the waste generation,the developed Pt-DICY catalysts have been successfully applied for the green industrial production of many important aniline intermediates.

Effects of Nitrobenzenes on DNA Damage in Germ Cells of Rats

The single cell gel electrophoresis （SCGE） technique was used to detect DNA damage in germ cells of rats, which was induced by five tested nitroaromatic compounds. Mixed cultures of Sertoli and germ cells were prepared from the rats testis and their responses to rn-dinitrobenzene （ m-DNB）, 2,4-dinitrotoluene （ 2,4-DNT）, 2,6-dinitroto-luene（2,6-DNT）, 4-nitrotoluene（4-NT） and 2,4-dinitroaniline（2,4-DNAn） were studied. The results show that all the five chemicals have a reproductive toxicity. Each dose group and the control group were significantly different （ P 〈 0. 01 ）. All of them can lead to the damage to DNA in the germ cells of Kunming male rats in the definite range of concentration（m-DNB ： 0. 04-25μmol/L; 2,4-DNT, 2,6-DNT and 4-NT： 0. 032-500μmol/L; 2,4-DNAn ：0. 8-20μmol/L）. When the concentration increases, the damage rate will become higher, which shows an evident logarithm dose-effect relationship.