Recent progress in controlling the synthesis and assembly of nanostructures: Application for electrochemical determination of p-nitroaniline in water

Selective identification of p-nitroaniline by bromine-mediated polarization of carbon dots

A fluorometric method based on boron, bromide-codoped carbon dots (BBCNs) was developed for the first time for the highly selective detection of p-nitroaniline (PNA) in wastewater samples. It should be noted that the introduction of bromine greatly increases the molecular polarizability of the probe, which can regulate the energy level matching between the probe and PNA, resulting in the interaction between BBCNs and PNA. In the presence of PNA, the fluorescence of BBCNs is obviously quenched and accompanied by a red shift of the fluorescence band, which might be attributed to the formation of aggregates caused by the polar adsorption of BBCNs and PNA. It is beneficial for constructing a highly selective sensing platform for PNA determination compared to its isomers (o-nitroaniline and m-nitroaniline) through atomic bromine-mediated polarization of the BBCNs. With the help of this mechanism, an excellent linear range of 0.5-300 μM with a low detection limit of 0.24 μM toward PNA was obtained. This work further confirms that there is a significant relationship between the nature of doping elements and the optical and physicochemical properties of fluorescent materials.

Synthesis of Prussian Blue Analogue and Its Catalytic Activity toward Reduction of Environmentally Toxic Nitroaromatic Pollutants

Nitroanilines are environmentally toxic pollutants which are released into aquatic systems due to uncontrolled industrialization. Therefore, it is crucial to convert these hazardous nitroanilines into a harmless or beneficial counterpart. In this context, we present the chemical reduction of 4-nitroaniline (4-NA) by NaBH₄ utilizing Prussian blue analogue (PBA) as nanocatalyst. PBAs can serve as inexpensive, eco-friendly, and easily fabricated nanocatalysts. PBA cobalt tetracyanonickelate hexacyanochromate (CoTCNi/HCCr) was stoichiometrically prepared by a facile chemical coprecipitation. Chemical, phase, composition, and molecular interactions were investigated by XRD, EDX, XPS, and Raman spectroscopy. Additionally, SEM and TEM micrographs were utilized to visualize the microstructure of the nanomaterial. The findings revealed the synthesized PBA of the cubic phase and their particles in nanosheets. The band gap was estimated from the optical absorption within the UV-vis region to be 3.70 and 4.05 eV. The catalytic performance of PBA for the reduction of 4-NA was monitored by UV-vis spectroscopy. The total reduction time of 4-NA by PBA was achieved within 270 s, and the computed rate constant (k) was 0.0103 s^-1. The synthesized PBA nanoparticles have the potential to be used as efficient nanocatalysts for the reduction of different hazardous nitroaromatics.

Biodegradation of 4-nitroaniline by novel isolate Bacillus sp. strain AVPP64 in the presence of pesticides

In this study, Bacillus sp. strain AVPP64 was isolated from diuron-contaminated soil. It showed 4-nitroaniline (4-NA) degradation, pesticide tolerance, and self-nutrient integration via nitrogen (N)-fixation and phosphate (P)-solubilization. The rate constant (k) and half-life period (t_1/2) of 4-NA degradation in the aqueous medium inoculated with strain AVPP64 were observed to be 0.445 d^-1 and 1.55 d, respectively. Nevertheless, in the presence of chlorpyrifos, profenofos, atrazine and diuron pesticides, strain AVPP64 degraded 4-NA with t_1/2 values of 2.55 d, 2.26 d, 2.31 d and 3.54 d, respectively. The strain AVPP64 fixed 140 μg mL^-1 of N and solubilized 103 μg mL^-1 of P during the presence of 4-NA. In addition, strain AVPP64 produced significant amounts of plant growth-promoting metabolites like indole 3-acetic acid, siderophores, exo-polysaccharides and ammonia. In the presence of 4-NA and various pesticides, strain AVPP64 greatly increased the growth and biomass of Vigna radiata and Crotalaria juncea plants. These results revealed that Bacillus sp. strain AVPP64 can be used as an inoculum for bioremediation of 4-NA contaminated soil and sustainable crop production even when pesticides are present.

Activity of Silver Nanoparticles against Staphylococcus spp

Staphylococcus epidermidis is a bacterium that is part of the human microbiota. It is most abundant on the skin, in the respiratory system and in the human digestive tract. Also, Staphylococcus aureus contributes to human infections and has a high mortality rate. Both of these bacterial species produce biofilm, a pathogenic factor increasing their resistance to antibiotics. For this reason, we are looking for new substances that can neutralize bacterial cells. One of the best-known substances with such effects are silver nanoparticles. They exhibited antibacterial and antibiofilm formation activity that depended on their size, shape and the concentration used. In this review, we presented the data related to the use of silver nanoparticles in counteracting bacterial growth and biofilm formation published in scientific papers between 2017 and 2021. Based on the review of experimental results, the properties of nanoparticles prompt the expansion of research on their activity.

An ultra-sensitive electrochemical sensor of Ni/Fe-LDH toward nitrobenzene with the assistance of surface functionalization engineering

Hypersensitive detection of organic pollutions with high toxicity in drinking water always keeps its challenge in electroanalysis due to their low concentration and electrochemical redox inert. In this work, a novel nanomaterial modified electrode for the sensitive detection of nitrobenzene (NB) is presented, based on environmental friendly and cost-effective Ni/Fe layered double hydroxides functionalized with sodium dodecyl sulfate (Ni/Fe(SDS)-LDH). Such 2D layered composites were prepared and used to improve the sensitivity for NB detection, due to its good catalytic activity for NB reduction. Besides, the proposed electrode shows a remarkably promoted sensitivity to NB compared to Ni/Fe-LDHs modified one. It is because that the surface modifier SDS can provide more adsorption sites to significantly improve the adsorption of NB, which has been confirmed by the adsorption experiment and the characterization of Fourier transform infrared spectroscopy (FTIR). As a result, an impressive sensing behaviour is achieved at the proposed Ni/Fe(SDS)-LDHs modified electrode with a sensitivity of 15.79 μA μM^-1 cm^-2. This work provides a promising way to build more advanced nanomaterials to electrochemical detection of organic pollution based on energetically synergizing of adsorption by surface functionalization engineering.

A comparative study of novel spectrophotometric methods for simultaneous determination of nitroaniline isomers in their binary mixtures with highly severe overlapping spectra

In the present work, four simple and economic spectrophotometric methods, namely constant center (CC), ratio difference (RD), H-point standard addition method (HPSAM), and ratio H-point standard addition method (RHPSAM) were employed for the simultaneous determination of meta and para-nitroaniline with severely overlapping spectra without unitizing the preliminary physical separation techniques. In each method, the parameters affecting the resolution of the spectra were optimized to determine the cited isomers in a binary mixture with a high accuracy. Under the optimized conditions, the results obtained showed that from cited methods used, the CC and RD methods have the least errors in determination of the concentration of highly spectral overlapping species. The mean percentage recovery values for the binary mixture of meta- and para-nitroaniline were found to be 95.98 and 98.78 using the RD method, and 101.85 and 100.23 using the CC method, respectively. For comparison of the powerful multivariate methods including the principal component regression (PCR) and partial least squares (PLS) were also applied. The mean percentage recovery values for the binary mixtures of the cited isomers were found to be 101.62 and 101.47 using the PCR method, and 101.00 and 101.36 using the PLS method, respectively. A statistical comparison of the methods demonstrated that there was no significant difference between the RD, CC, PCR, and PLS methods and the reported HPLC method regarding both accuracy and precision. The proposed methods have an admissible precision and accuracy for determination of the two isomers in their binary mixtures in tap water as a real sample.