Showing papers on "Nitrobenzene published in 2023"

AIEE active stilbene based fluorescent sensor with red-shifted emission for vapor phase detection of nitrobenzene and moisture sensing

Abstract: A unique π-electron rich stilbene-based sensor with significantly enhanced red-shifted fluorescence emission has been synthesized via a Mizoroki-Heck cross-coupling reaction. The strong fluorescence properties of stilbene derivative as a potential fluorescent sensor have been investigated for sensitive and selective detection of hazardous and threatening nitrobenzene (NB) in both solution and vapor phase. The fluorescence emission intensity of stilbene sensor 1 at 474 nm was quenched upon interaction with NB. The fluorescence quenching was attributed to the combined effect of dominant smaller and adjustable size of NB and photo-induced electron transfer (PET) process. Stilbene sensor 1 is the first active bathochromic shifted fluorescent sensor with AIEE property was developed for both solution and vapor phase detection of NB. Possible interactions of stilbene sensor 1 with NB was evaluated by UV–vis., fluorescence, density functional theory (DFT) calculations, and 1H NMR titration experiment. Additionally, non-covalent interaction (NCI), Frontier molecular orbitals (FMOs) and interaction energy were studied by using Gaussian 09 software. Moreover, test strips were fabricated to accomplish contact mode detection of NB. Further, stilbene sensor 1 was successfully applied for trace detection of NB in real water samples.

Voltammetric Sensor Based on Waste‐Derived Carbon Nanodots for Enhanced Detection of Nitrobenzene

Abstract: Carbon dots (CDs) samples were synthesized from orange peel waste (OPW) via a simple and eco-friendly hydrothermal carbonization (HTC) and electrochemical (EC) bottom-up synthesis integrated approach. The comprehensive chemical-physical characterization of CDs samples, carried out by various techniques such as TEM, EDX, XRD, FT-IR, underlined their morphological and microstructural features. The CDs exhibited attractive electrochemical properties, and thus an electrochemical sensor by modifying a screen printed carbon electrode (CDs/SPCE) for the detection of nitrobenzene (NB) in water was developed. Electroanalytical performances of CDs/SPCE sensor using differential pulse voltammetry (DPV) demonstrated its high sensitivity (9.36 μA μM−1 cm−2) towards NB in a wide linear dynamic range (0.1–2000 μM) and a low limit of detection (LOD=13 nM). The electrochemical sensor also shown high selectivity, long-term stability, and repeatability. This paper might open the way to a new synergistic HTC-EC approach for the synthesis of CDs from waste biomass material and their advanced application in highly efficient electrochemical sensors.

Flower-like strontium molybdate anchored on 3D N-rich reduced graphene oxide aerogel composite: An efficient catalyst for the detection of lethal pollutant nitrobenzene in water samples

Abstract: Nitrobenzene (NB) is a carcinogenic water pollutant that can have dangerous effects on humans, animals, and the environment even in trace amounts. It can persist in contaminated sites and leach into the adjacent aquatic environment. Therefore, the detection of trace amounts of NB is of great interest. To address this challenge, we have fabricated strontium molybdate microflowers (SrMoO4, SMO MFs) grown on nitrogen-rich, porous three-dimensional (3D) reduced graphene oxide aerogels (SMO/N-rGO) for sensitive detection of NB in water samples. The 3D N-rGO and SMO/N-rGO composites were prepared by simple hydrothermal and precipitation methods. The fabricated SMO/N-rGO composites exhibited a porous and 3D structure with a strong synergistic effect between the SMO MFs and the N-rich porous rGO sheets with open voids that facilitate the diffusion of NB. The electrochemical detection of NB at the SMO/N-rGO modified electrode was significantly enhanced. Using amperometry (i-t), the modified SMO/N-rGO sensor was shown to have two linear response ranges in the sensing of NB, with the lower linear concentration range from 7.1 nM to 1.0 mM and the higher linear concentration range varying from 1.1 mM to 2.5 mM. In addition, the limit of detection (LOD) was calculated to be 2.1 nM using the amperometric (i-t) technique. Common nitro derivatives, biomolecules, and cations often found in water systems had no influence on the detection of NB. At the same time, a good recovery of 96.1–99.6% was obtained for real-time monitoring analysis in tap and lake water samples. In this work, new electrochemical sensors for monitoring various pollutants are developed based on anchoring conductive metal oxide electrocatalysts on porous 3D carbon aerogels.

Cover Feature: Voltammetric Sensor Based on Waste‐Derived Carbon Nanodots for Enhanced Detection of Nitrobenzene (ChemElectroChem 13/2023)

Abstract: The Cover Feature shows groundwater contaminated by environmental pollutants and how a sensor modified by an improved waste is helpful to estimate the presence of contaminants in it. The electrochemical sensors are crucial in the technology for the detection of contaminants, thanks to their simplicity and reusability. The eco-friendly Carbon Dots obtained from fruit peels waste by a bottomup electrochemical synthesis are chemically perfect for the purpose. Cover design by C. Michenzi. More information can be found in the Research Article by V. Bressi et al.

Stepwise Growth of Copper-Based Coordination Polymer on α-MnO2 Nanorods for Sustainable Reduction of Nitroarenes

Abstract: Metal oxide/coordination polymer composites have gained great attraction due to their synergistic effects to increase their efficiency in various fields. In this work, a Cu-based coordination polymer (Cu-CP) was grown on the surface of α-MnO2 nanorods via stepwise assembly of benzene-1,4-dicarboxylic acid (H2BDC) as a ligand and a Cu(II) ion as a metal center. Comprehensive characterization techniques confirmed the successful growth of Cu-CP on the surface of α-MnO2 without affecting the morphology of pristine α-MnO2 nanorods. The obtained nanocomposite (α-MnO2/Cu-CP) revealed outstanding activity in the catalytic reduction of nitroarenes to aminoarenes under mild reaction conditions and afforded wide substrate applicability (more than 99% for nitrobenzene and 70–99% for other substituted nitroarenes during 1 h at room temperature). Importantly, α-MnO2/Cu-CP served as a better catalyst than bare α-MnO2 and Cu-CP due to the synergistic effects between building components. In addition, α-MnO2/Cu-CP was easily separable by centrifugation and its catalytic activity remained unaffected over five cycles. The use of water as a sustainable and green solvent and non-toxic and inexpensive metals used for the synthesis of the catalyst along with easy recovery and stability of the catalyst make the present protocol economical and sustainable. The time-dependent reduction kinetics followed pseudo-first-order kinetics with respect to the substrates.

Selective Photocatalytic Reduction of Nitrobenzene to Aniline Using TiO2 Embedded in sPS Aerogel

Abstract: In recent years, aromatic substances have become the focus of environmental pollution-related concern due to their high stability and mutagenicity. In this regard, researchers have focused their attention on the development of photocatalytic processes to convert nitroaromatic compounds into aniline. In this work, the photocatalytic conversion of nitrobenzene (NB) to aniline (AN) was studied. The photocatalytic reaction was performed using commercial TiO2 (P25) and a photocatalytic aerogel, based on P25 embedded in syndiotactic polystyrene (sPS) aerogel (sPS/P25 aerogel) as photocatalysts. Different alcohols were used as hydrogen sources during the photocatalytic experiments. At the optimized operating conditions (photocatalysts dosage: 0.5 mg/L and 50% (v/v) EtOH%), an AN yield of over 99% was achieved. According to the results, this work could open avenues toward effective production of AN from NB using mild reaction conditions with sPS/P25 aerogel—in view of a possible scale-up of the photocatalytic process.

Silver-assisted reduction of nitroarenes by an Ag-embedded curcumin/melamine-functionalized magnetic nanocatalyst

Abstract: In the current study, we introduce a hybrid magnetic nanocomposite comprised of curcumin (Cur), iron oxide magnetic nanoparticles (Fe3O4 MNPs), melamine linker (Mel), and silver nanoparticles (Ag NPs). Initially, a facile in situ route is administrated for preparing the Fe3O4@Cur/Mel-Ag effectual magnetic catalytic system. In addition, the advanced catalytic performance of the nanocomposite to reduce the nitrobenzene (NB) derivatives as hazardous chemical substances were assessed. Nevertheless, a high reaction yield of 98% has been achieved in short reaction times 10 min. Moreover, the Fe3O4@Cur/Mel-Ag magnetic nanocomposite was conveniently collected by an external magnet and recycled 5 times without a noticeable diminish in catalytic performance. Therefore, the prepared magnetic nanocomposite is a privileged substance for NB derivatives reduction since it achieved notable catalytic activity.

A corrected benzene nitration three-step mechanism derived by DFT calculation and MO theory

Abstract: Density-functional theory (DFT) calculations at the LC-wHPBE/6-311++G(d,p) level found that the textbook three-step nitration mechanism of benzene in mixed acids was seriously wrong. Step 1 of generating nitronium ion (NO2+) is not spontaneous, the NO2+ is generated by Lewis collision, and needs to overcome a barrier Ea = 18 or 22 kcal/mol in mixed acid or in nitric acid. Obtaining the Ea of the Lewis collision by quantum chemical calculations is a highlight of the study. The reaction system (NO2+ + H2O) + HSO4⎺ or + NO3⎺ or + nH2O (n ≥ 1) can make NO2+ spontaneously change to HNO3 through a poly(≥3)-molecular acidification. Sulfuric acid can greatly reduce [H2O] and increase [NO2+]. Therefore, the nitration rate in mixed acid is much faster than that in nitric acid. Step 2, C6H6 + NO2+, is an electrophilic addition, follows the transition state theory, and needs to overcome a low barrier, ΔE* = 7 kcal/mol. The product of Step 2 is the σ-complex C6H6-NO2+. The essence of the electrophilic addition is the transfer of HOMO-1 electrons of C6H6 to LUMO of NO2+. Step 3 is a spontaneous Lewis acid-base neutralization without any barrier, and generates the target product nitrobenzene C6H5NO2. NO2+ and σ-complex are the two active intermediates in nitration. The benzene nitration rate control step is not Step 2 of generating σ-complex, but is Step 1 to generate NO2+. The DFT calculation obtains the barriers Ea and ΔE*, the reaction heats ΔHσ and ΔHp of each step of the nitration, resulting in the total nitration reaction heat ΔH = -35 kcal/mol. It is consistent with the experimental ΔH = -34 kcal/mol. Based on the results, a corrected benzene nitration three-step mechanism proposed.

Active Pd Catalyst for the Selective Synthesis of Methylated Amines with Methanol.

Abstract: Selective N-methylation of amines with methanol is an important reaction in the synthesis of high-value-added fine chemicals, including dyes, surfactants, pharmaceuticals, agrochemicals, and materials. However, N-methylated amines possess higher reactivities and are prone to further transform into N,N-dimethylated amines. Therefore, it is still a challenge to controllably regulate the selectivity of N-methylation using heterogeneous catalysts without the use of base. Herein, we developed a series of Pd/Zn(Al)O catalysts with abundant basic sites, and the selectivity of N-methylation was controlled by a heterogeneous Pd/Zn(Al)O catalyst with a Zn/Al ratio of 10 and a Pd loading of 0.4 wt % in the pressure of H2. The experimental results showed that the appropriate basic properties of the catalyst were beneficial to form the desired N-methylated amine. The low loading of Pd in the catalyst was highly dispersed on the support, providing sufficient active sites. These were attributed to the Zn vacancies formed by Al-doped Zn, which were beneficial to form the highly active and stable Pd sites. Furthermore, a series of amines and nitrobenzenes with different functional groups were well tolerated for the selective synthesis of N-methylated amines in the absence of base.

Synthesis of Mesoporous Silica-Supported NiCo Bimetallic Nanocatalysts and Their Enhanced Catalytic Hydrogenation Performance

Abstract: In this work, mesoporous silica SBA-16-supported NiCo bimetallic nanocatalysts were synthesized by coimpregnation of Ni and Co precursors followed by calcination and reduction, and various characterization techniques confirm the formation of NiCo bimetallic nanostructures in the catalysts. The synthesized NiCo/SBA-16 shows enhanced catalytic performance for hydrogenation of a series of nitroaromatics. Under the reaction conditions of 80 °C and 1.0 MPa of H2, the yields of aniline for nitrobenzene hydrogenation over NiCo0.3/SBA-16 can reach more than 99% at 2.0 h. The enhanced catalytic performance can be ascribed to the formation of NiCo bimetallic nanostructures, where the synergistic effect between Ni and Co improves their catalytic activities for hydrogenation of nitroaromatics.

Copper Foam-Supported CuxO@Fe2O3 Core–Shell Nanotubes: An Efficient Ozonation Catalyst for Degradation of Organic Pollutants

Abstract: Copper foam (CF)-supported CuxO@Fe2O3 core–shell nanotubes (CF/CuxO@Fe2O3 NTs) were synthesized as a hybrid catalyst for heterogeneous catalytic ozonation (HCO). The hybrid catalyst exhibits high activity and excellent stability for the HCO of organic pollutants. The total organic carbon removal rates of methyl orange, ibuprofen, and nitrobenzene via HCO were 89, 82, and 88%, respectively, which are over 2 times higher than the corresponding values obtained without the catalyst. The hybrid catalyst also displays wide pH operation range, low metal leaching, easy separation from treated water, and excellent recyclability. We prove that large amounts of Lewis acid sites with medium acidity are created at the CuxO/Fe2O3 interface due to the synergic effect of CuxO and Fe2O3. These medium acid sites are the main active centers for the production of free hydroxyl radicals (•OH) and superoxide radicals (O2•– or HO2•) in neutral solution. Moreover, the 3D porous framework of the catalyst enables easy dispersion in and separation from water. This work develops a new strategy to design HCO catalysts by combining strong and weak Lewis acid oxides and also opens a new avenue for developing HCO catalysts on a 3D porous framework.

Gold Nanoparticles Immobilized in Porous Aromatic Frameworks with Abundant Metal Anchoring Sites as Heterogeneous Nanocatalysts.

Abstract: Porous aromatic frameworks (PAFs) with rich metal coordination sites are highly effective support materials for gold nanoparticles (AuNPs), which would not only prevent AuNPs agglomeration but also facilitate mass transfer during the catalytic process. In this work, PAF-160, -161, and -162 bearing diphosphine units are synthesized via the Friedel-Crafts alkylation reaction to act as efficient platforms for AuNPs immobilization. These PAFs possess high surface areas (up to 655 m2 g-1) together with excellent stabilities, and the different linkage lengths between P centers allow more scattered and accessible sites for gold coordination. In the resultant Au-PAFs, AuNPs with uniform sizes are stabilized dispersedly. The catalytic performances of these Au-PAFs are monitored by the reduction of 4-nitrophenol (4-NP), and all materials exhibit excellent catalytic activities on the reduction of 4-NP, especially Au-PAF-162 with the apparent rate constant (kapp) up to 0.019 s-1. Additionally, the reductions of various nitroarenes with different functional groups are explored and all Au-PAFs can convert most nitroaromatic derivatives to the corresponding arylamines with high conversions of 99%, in which the reaction mechanism is also proposed. Furthermore, a continuous catalytic device with Au-PAF-160 catalyst is explored, and Au-PAF-160 can convert 1-chloro-4-nitrobenzene, 2,6-dichoronitrobenzene and 1-chloro-2,4-dinitrobenzene into the corresponding amines in sequence in the continuous flow catalytic experiments. This work has enriched the variety of porous materials for noble metal immobilization and promotes their applications in heterogeneous catalysis.

Synergistic effect of acid-base and redox properties of nano Au/CeO2-cube on selective hydrogenation of nitrobenzene to aniline

Abstract: Catalysts with 1 wt% gold doped on various morphologies of ceria (nano-cubes, nano-rods and nano-polyhedra), were prepared by the deposition precipitation method. The samples are characterized and used to catalyze the hydrogenation of nitrobenzene in ethanol. The highest nitrobenzene conversion (92%) and aniline selectivity (90%) are achieved from the catalyst supported by nano-cube CeO2 (1 wt% Au/CeO2-cube). The calcination temperatures of both the support and catalyst can influence the acid-base properties, the morphology and the valance of Au and Ce, which are key factors in the adsorption of nitrobenzene, the desorption of aniline and the formation of active H− species, respectively. We find that small-size Au nanoparticles (2.1 nm) with appropriate ratio of Au0 to Auδ+, acid/base sites with sufficient density and appropriate strength, and oxygen vacancy of ceria on the interface of Au and ceria are favorable to the formation of aniline on 1 wt% Au/CeO2-cube.

Kinetic evaluation of heterocatalytic ozone-based activation of peroxymonosulfate using acid-treated graphene catalyst for the degradation of micropollutants

Abstract: In this study, acid-treated graphene (Gr⎯COOH) catalyst was synthesized using a microwave plasma reactor, and its performance in different combinations of ozone and ozone activated peroxymonosulfate (O3, O3+Gr⎯COOH, O3+PMS, and O3+PMS+Gr⎯COOH) was kinetically evaluated. The yields of SO4•⎯ and HO• were quantified based on ozone consumption. Among the different operating parameters, the effect of pH (4−8) was particularly considered. The results showed that heterocatalytic ozone-based activation of peroxymonosulfate performed efficiently at neutral and alkaline conditions. The first-order rate constants for O3 decomposition in O3+PMS+Gr⎯COOH (1.2×10−2s−1) was higher than O3+PMS (8.5×10−3s−1) and O3 (2×10−4s−1) by a factor of 1 and 2 respectively. The radical yields were positively associated with pH. Higher pH values showed a notable increase in radical yields (η), with the maximum value of ηTotal (0.88) and ηHO• (0.53) obtained at pH 8 while ηSO4•⎯ showed maxima (0.46) at pH 7. This implies that at higher pH i.e., 8, HO• was the dominant reactive specie, which could be due to the presence of higher concentration of HO− and transformation of SO4•⎯ into HO•. Furthermore, the synergistic effects of the oxidative processes were tested considering atrazine (ATZ, 1 µM) and nitrobenzene (NB, 1 µM) as probe compounds. The best performance was obtained with O3+PMS+Gr⎯COOH process, reaching 96% and 81% of ATZ and NB removal respectively. The suppressive effects of inorganic ions and natural organic matter (NOM) on the degradation efficiency of ATZ and NB were also lower for O3+PMS+Gr⎯COOH process. These results confirmed that acid-treated graphene (Gr⎯COOH) catalyst in combination with ozone activated peroxymonosulfate could be an efficient and promising alternative oxidative process.

Giant Premelting Effects for Solid–Liquid Discontinuous Transition in Nitrobenzene under Compression

Abstract: This report presents ‘giant’ and long-range premelting effects appearing in dielectric properties for the temperature and pressure paths of studies, with an explicit critical-like portrayal. The result was obtained for the ‘classic’ low molecular weight compound: nitrobenzene, tested in the solid and liquid phases. Dielectric studies enable the ‘extraction’ of the response from liquid layers between crystalline grains. Compressing increased the premelting effects, probably due to the ‘crushing’ of crystalline grains by isotropic squeezing and increasing the liquid layers between grains. This report indicates the significance of considering the melting/freezing phenomenon from the point of view of the ‘solid crystalline grains and critical-type liquid layers in synergic interactions’ concept.

Weak Affinity Chromatography using Organic Solvents on Cyanopropyl- and Arene-Modified Silica-Gel Columns—Structural Demands for Host and Guest Moieties and Effect of Solvents

Abstract: Weak affinity chromatography (WAC) is effective for isolating target compounds from analogous compounds with similar functional groups. Previously, a few chromatographic behaviors based on WAC using organic solvents were observed in a series of cyclic multiporphyrin systems on cyanopropyl-modified silica gel (CN-MS). Here, three cyclic porphyrin trimers with various rigidity were examined on CN-MS to understand the mechanism of the specific interactions between porphyrin derivatives and functional groups on modified silica gel. In addition to CN-MS, six modified silica-gel columns were tested to compare their retention abilities for a cyclic nickel porphyrin dimer (C4Ni2MsCP2). We examined the cosolvent effects of the pyridine eluents for C4Ni2MsCP2. Apparent dissociation constants of C4Ni2MsCP2 with functional groups on the MS columns and effective amounts of the functional groups were estimated by frontal affinity chromatography (FAC). 1H NMR titrations of acetonitrile and nitrobenzene to C4Ni2MsCP2 were conducted to compare their association constants with movable guest molecules to the dissociation constants with immobilized functional groups obtained in FAC. We found rigidity of cyclic porphyrin derivatives and immobilization of functional groups on silica gel is necessary for significant retentions using WAC. The affinity interaction does not occur at the center of C4Ni2MsCP2, but probably occurs on the surface composed of a bipyridyl moiety and the adjacent edges of the two porphyrins. Polar solvents, such as nitrobenzene, acetonitrile, and methanol, weakened the interaction. Although C4Ni2MsCP2 dissolves well in chloroform, the interactions between C4Ni2MsCP2 and the MS columns are considerably strengthened in the presence of chloroform. The competitiveness of solvents and cosolvents with the interaction of the porphyrin on WAC is independent of the solubility of the analyte.