Aggregated gold nanoparticles rich in electromagnetic field "hotspots" for surface enhanced Raman scattering.

A simple method for one-step synthesis of aggregated gold nanoparticles (a-AuNPs) using single-layer carbon dots (s-CDs) as the capping agents has been proposed. The obtained a-AuNPs are mainly composed of several spherical AuNPs of 20-25 nm sized, which aggregate to form nanogaps of ∼1 nm. Furthermore, the obtained a-AuNPs produce a strong localized surface plasmon resonance (LSPR) absorption band centered at around 640 nm, which is quite close to the wavelength of the commonly used 633 nm laser in surface enhanced Raman scattering (SERS). Thus, under the irradiation of 633 nm laser, a lot of electromagnetic field "hot spots" are formed at around the nanogaps, and strong SERS activity is achieved. The obtained a-AuNPs are dropped on tin-foil wafers to fabricate SERS substrates, which show the advantages of high sensitivity, fast response, good repeatability and satisfactory stability. On the basis, a sensitive SERS sensor is developed to detect malachite green in aquaculture water, with a low detection limit of 1 × 10-9 mol/L.

Three-dimensional NTF-Ag composites for ultrasensitive SERS-based detection of malachite green on crucian carp skin.

Three-dimensional (3D) Na2Ti3O7 flower (NTF) systems were synthesized, followed by sputter coating with silver (Ag) nanoparticles to increase surface-enhanced Raman scattering (SERS) activity. By varying the sputtering time, SERS activity of the Ag-decorated NTF (NTF-Ag) structures was optimized. Furthermore, the theoretical evidence from finite difference time domain (FDTD) simulations confirmed that an appropriate density of Ag particles increased the electromagnetic field contribution. The electromagnetic field contribution is high because the special petal-shaped structure can promote multiple reflections and scattering, thus providing efficient resonance absorption for charge-transfer (CT) and exciton enhancements. Highly SERS-active NTF-Ag composites were developed and exploited for the detection of malachite green (MG), a model contaminant in the food industry. The detection limit of this method for MG reached 3.78 × 10-10 M, with a standard deviation of homogeneity of 6.83 %. This method was successfully applied to detect MG on crucian carp skin, and it showed high recovery, indicating that it can serve as a practical method for MG evaluation. All results demonstrated that the prepared NTF-Ag composite has great potential in the application of SERS-based contamination assessment in the food industry.

Magnetic covalent organic framework as an absorbent coupled with a portable mass spectrometer for rapid detection of malachite green and its metabolite residues.

It is important to develop specific adsorbents for malachite green and other fish drug residues. Herein, a simple strategy for synthesizing a novel magnetic covalent organic frameworks (rFe3O4@Py-COF) has been studied, and the materials were used as a magnetic absorbent for solid phase extraction (MSPE) of malachite green (MG) and its metabolite as leucomalachite green (LMG) in fishes. In this study, the mild reduction program of formic acid replacing traditional sodium borohydride as a reducing agent has been adopted to increase the stability of the framework, which can maintain the original high crystallinity and surface area of the reduced COF. The secondary amine bond is expected to be used as the reaction center for further functionalization of COF pore wall. Subsequently, rFe3O4@Py-COF (rmCOF) obtained after reduction was used as MSPE materials to detect MG and LMG by a portable mass spectrometer. After optimizing the conditions, the linearity is good within the range of 1.25∼100 µg/kg (R2≥0.9954), the limits of detection (LODs) are 0.31∼0.44 µg/kg with satisfactory recovery (85.0 %∼106.0 %). These results indicate that the assay is suitable for monitoring MG and LMG in complex aquatic foods, providing protection for food safety.

Biofabrication of highly effective and easily regenerated CuO nanoparticles as adsorbents for Congo red and malachite green removal.

An effective and easily regenerated adsorbent is the one for which scientists are making an effort to explore. In this study, copper oxide nanoparticles (CuO NPs) were synthesized in a green manner from a leaf extract of Moringa stenopetala and used for dye adsorption. XRD, FTIR, and SEM were employed for the characterization of CuO NPs. The crystallite size of the CuO NPs was calculated via Debye-Scherrer equation from the XRD data and was found to be 8.33 nm. The Cu-O bonding bending vibration at 1116 cm- 1 and stretching vibration at 1649 cm- 1 observed from the FTIR data strongly confirmed the formation of CuO NPs. SEM morphology analysis confirmed the formation of nanoparticles with a plate-like morphology and a spherically random orientation. The zero-point charge of CuO NPs was investigated and reported to be at pH 7. The adsorption of dyes on the greenly produced CuO NPs was studied by optimizing different adsorption parameters. The removal efficiencies of the green CuO NPs adsorbent were 99.54% at the optimum conditions (pH, 4; dye concentration, 30 mg/L; amount of adsorbent, 0.25 g; and contact time, 80 min) and 98.33% at the optimum conditions (pH, 11; dye concentration, 20 mg/L; amount of adsorbent, 0.4 g; and contact time, 80 min) for congo red and malachite green, respectively. The adsorption efficiency of the biosynthesized CuO NPs for the mixture of the two dyes was 92.3%. The green synthesized adsorbent was regenerated and able to work effectively for four cycles for the two dyes. The results of the kinetics-type investigation indicate that the adsorption of both dyes by the CuO NPs adsorbent best fits a pseudo-second-order model. The isotherm model-type investigation resulted in the fitting of the Langmuir adsorption isotherm for both the congo red and malachite green dyes.

A Novel Sensing Method to Detect Malachite Green Contaminant on Silicon Substrate Using Nonlinear Optics.

We propose a nonlinear-optics-based nanosensor to detect malachite green (MG) contaminants on semiconductor interfaces such as silicon (Si). Applying the simplified bond hyperpolarizability model (SBHM), we simplified the second-harmonic generation (SHG) analysis of an MG-Si(111) surface and were able to validate our model by reproducing experimental rotational anisotropy (RA) SHG experiments. For the first time, density functional theory (DFT) calculations using ultrasoft pseudopotentials were implemented to obtain the molecular configuration and bond vector orientation required by the SBHM to investigate and predict the second-harmonic generation contribution for an MG-Si 001 surface. We show that the SBHM model significantly reduces the number of independent components in the nonlinear tensor of the MG-Si(111) interface, opening up the possibility for real-time and non-destructive contaminant detection at the nanoscale. In addition, we derive an explicit formula for the SHG far field, demonstrating its applicability for various input polarization angles. Finally, an RASHG signal can be enhanced through a simulated photonic crystal cavity up to 4000 times for more sensitivity of detection. Our work can stimulate more exploration using nonlinear optical methods to detect and analyze surface-bound contaminants, which is beneficial for environmental monitoring, especially for mitigating pollution from textile dyes, and underscores the role of nonlinear optics in real-time ambient-condition applications.

Carboxymethyl cellulose assisted morphology controlled synthesis of Mn3O4 nanostructures for adsorptive removal of malachite green from water.

The physicochemical properties of manganese oxides and their different applications mainly depend upon their crystallite size, morphology, phase structure, and surface properties, which are again dependent on the preparation methods. So, a simple, cost-effective, and versatile synthesis method for such materials is highly desirable. Intending to accomplish this, herein we report the synthesis of Mn3O4 nanostructures by alkaline hydrolysis of the corresponding metal ions in an aqueous medium. The addition of a biodegradable polymer, sodium salt of carboxymethyl cellulose (Na-CMC) assisted the development of specific morphology, which is tunable by varying the concentration of the biopolymer. The spectroscopic, microscopic, and diffractometric analyses of the synthesized Mn3O4 nanostructures confirm that this particular simple technique is very effective in controlling the morphology of the formed nanostructures. These Mn3O4 nanostructures exhibit excellent adsorption capacity in the removal of malachite green (MG) from its aqueous solution under ambient conditions. The adsorption process is exothermic following pseudo-second-order kinetics with a maximum dye adsorption capacity of 489.68 mg g-1 according to the Sips isotherm model. The Mn3O4 nanostructures can be reused for up to five cycles of dye adsorption without significant loss of their adsorption performance.

Novel tempo oxidized polyvinyl alcohol/ cellulose nanocrystal-based nanocomposite membrane for malachite green dye removal.

In this study, in-situ modification by TEMPO oxidation was performed after nanocomposite synthesis to improve its properties toward dye molecule removal. The unoxidized and oxidized polymeric-based nanocomposite was denoted as PNC6 and PNC6O respectively. The nanocomposites were characterized using FESEM, FTIR, contact angle, XRD and BET analysis. Measurements of swelling ratio and chemical stability were also performed to provide insight into the durability of the nanocomposites. The effects of changing variables included contact duration, pH of aqueous solution, initial pollutant concentration, and temperature were observed. The kinetic study showed that the experimental data is best fitted with pseudo-second-order kinetics (R2 = 0.988 and 0.997 respectively), whereas on observing isotherm data, in both unoxidized and oxidized nanocomposite it fits well with Langmuir isotherm (R2 = 0.951 and 0.993 respectively). In addition, the effects on Gibb's free energy, Enthalpy, and Entropy were measured in terms of thermodynamic characteristics, it was established that dye molecules adsorption mechanism is endothermic and spontaneous in behaviour. To check regeneration tendency of the nanocomposite seven consecutive adsorption desorption cycles were run and about 90% and 80%, regeneration ability could be seen in an unoxidized state (PNC6) and an oxidized state (PNC6O) respectively upto 5th cycle after that the tendency get reduced. This study suggests that this novel polymeric nanocomposite can be employed as an efficient and relatively inexpensive adsorbent for dye removal from aqueous solutions.

Elevating electron transfer of recyclable SERS sensor using AuNPs/TiO2/Ti3C2 heterostructures for detection of malachite green in sunfish.

Malachite green (MG)-contaminated aquatic products pose a serious threat to animal and human health. Hence, a novel recyclable surface-enhanced Raman scattering (SERS) substrate based on AuNPs/TiO2/Ti3C2 heterostructures was developed for the detection and degradation of MG in aquatic products. Specifically, AuNPs/TiO2/Ti3C2 heterostructures were synthesized by in situ oxidation and electrostatic adsorption based on Ti3C2 nanosheets. The excellent photocatalytic and SERS performance of the AuNPs/TiO2/Ti3C2 was demonstrated by Density functional theory (DFT) calculations and experimental results, which was attributed to the enhancement of charge transfer (CT) after the formation of heterostructures. The results demonstrate that AuNPs/TiO2/Ti3C2 is highly sensitive and recyclable. The detection limit of the sensor for MG is 8.91 × 10-5 mg/L. The sensor can be recycled for five times under the condition of light, and shows satisfactory self-cleaning performance in the food matrix, providing a possible alternative solution for the recyclable detection of MG.

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.

Dual-color immunochromatographic test strip for simultaneous sensitive detection of malachite green and leucomalachite green residues in fish and shrimp meat samples.

A sensitive dual immunochromatographic test strip (dual-ICTS) was developed to detect malachite green (MG) and its metabolite, leucomalachite green (LMG), using two types of gold nanoparticles: round-shaped (red) and star-shaped (blue). The detection limits were determined to be 0.221 µg L-1 for MG and 0.214 µg L-1 for LMG, respectively. The dual-ICTS provided a cut-off value of 1.8 µg L-1 for MG and LMG detection. The dual-ICTS successfully detected MG and LMG in food samples, with recovery rates ranging from 86 % to 116 %. The dual-ICTS was evaluated by correlation analysis between the proposed assay and the well-established enzyme-linked immunosorbent assay in the MG and LMG detection. This is the first report on the development of the ICTS that can detect both MG and LMG at the same time within only 5 min, making it a sensitive and rapid tool for on-site detection.

Enhancing Fenton-like reaction mediating performance of covalent organic frameworks through porosity modification.

Covalent organic framework (COF) catalytic photocatalysts mediating Fenton-like reactions have been applied to the treatment of organic dyes in printing and dyeing wastewater. However, the photocatalytic performance of original COF is often unsatisfactory. This study investigated the impact of porosity modification strategies on the performance of COF photocatalysts in mediating the removal of organic dyes via Fenton-like reaction. Porosity modification was achieved by increasing the concentration of acetic acid (HAc) catalyst during COF preparation. The modified TAPB-DMTA COF (12M COF) exhibited excellent adsorption and photocatalytic properties. The Fenton-like reaction mediated by 12M COF photocatalysis removed nearly 96% of malachite green (MG) within 20 min, with a rate constant of 0.091 min-1, which was 2.9 and 6.5 times higher than that of g-C3N4 and original COF under the same reaction conditions, respectively. Additionally, the modulation mechanism of porosity modification on COF photocatalysis was explored. The conduction band (CB) of COF was reduced from -0.14 eV to -0.38 eV after porosity modification, facilitating the generation of longer-lived O2•- in the reaction system, which was conducive to efficient MG removal. Anti-interference experiments showed that the photocatalytic Fenton-like reaction system based on 12 M COF was less affected by common anions, cations and dissolved organics, while maintaining a high MG removal rate in tap water, mid-water, secondary clarifier effluent and river water. In summary, porosity modification was an effective strategy to improve the catalytic performance of original COFs. This study presented an efficient metal-free photocatalyst modification strategy for the Fenton-like reaction while avoiding the production of toxic by-products during dye degradation.

A simple color absorption analysis of colorimetric loop-mediated isothermal amplification for detection of Raillietina spp. in clinical samples using a 3D-printed tube holder coupled with a smartphone camera and notebook screen.

A simple method has been developed for semi-quantitative analysis of the colorimetric output of loop-mediated isothermal amplification (LAMP) using a 3D-printed tube holder with a smartphone and notebook for the detection of Raillietina, which is the cause of Raillietiniasis affecting free-range chicken farming. In this method, a light is directed from a notebook screen to the LAMP products in the tube holder and the color absorption of the LAMP products is measured by using the appropriate smartphone application. It was found that the malachite green dye-coupled LAMP (MaG-LAMP) assay showed the highest sensitivity and specificity for detecting Raillietina without any cross-reaction with other related parasites and hosts. The limit of detection was 10 fg/µL of DNA. A total of 60 fecal samples were infectively confirmed by microscopic examination and the results of microscopy compared with those of MaG-LAMP and triplex PCR assays. Microscopy and MaG-LAMP based on the color absorption demonstrated high agreement in Raillietina detection with kappa = 1. Rapid, simple, cost-effective, and easy interpretation of colorimetric LAMP assays and their high sensitivity make them superior to PCR and morphological investigation, demonstrating the feasibility of this assay in point-of-care screening to support farm management and solve chicken health problems. Our study presents is an alternative diagnostic method using semi-quantitative analysis of colorimetric LAMP based on the differing solution color absorptions between positive and negative reactions for infectious disease diagnosis.

Impact of Chemical Dynamics of Commercial PURE Systems on Malachite Green Aptamer Fluorescence.

The malachite green aptamer (MGapt) is known for its utility in RNA measurement in vivo and in lysate-based cell-free protein systems. However, MGapt fluorescence dynamics do not accurately reflect RNA concentration. Our study finds that MGapt fluorescence is unstable in commercial PURE systems. We discovered that the chemical composition of the cell-free reaction strongly influences MGapt fluorescence, which leads to inaccurate RNA calculations. Specific to the commercial system, we posit that MGapt fluorescence is significantly affected by the system's chemical properties, governed notably by the presence of dithiothreitol (DTT). We propose a model that, on average, accurately predicts MGapt measurement within a 10% margin, leveraging DTT concentration as a critical factor. This model sheds light on the complex dynamics of MGapt in cell-free systems and underscores the importance of considering environmental factors in RNA measurements using aptamers.

[Synergistic removal of malachite green and Cr(â ¥) using ethylenediamine disuccinic acid functionalized silica gel].

As common industrial raw materials, malachite green (MG) and Cr(Ⅵ) generally coexist in waste liquids discharged from the paper printing, leather, and textile industries, causing serious harm to humans and the environment. Therefore, developing an effective method for the synergistic removal of MG and Cr(Ⅵ) from aquatic environments is of great research value. In this work, the non-homogeneous Fenton-like catalysts, namely, EDDS-Silica and EDDS-Co2+-Silica were successfully prepared using ethylenediamine disuccinic acid (EDDS) and silica gel (Silica) as raw materials, and a non-homogeneous Fenton-like catalytic method was developed for the efficient and synergistic removal of MG and Cr(Ⅵ) from wastewater. EDDS-Silica and EDDS-Co2+-Silica were analyzed using Fourier infrared spectroscopy and X-ray photoelectron spectroscopy to determine their structural composition and elemental contents. The catalytic degradation and removal effects of these materials in an MG single-waste system were also investigated. The results demonstrated that the incorporation of both materials can overcome the limitation of the conventional Fenton reaction, which is its applicability to acidic environments only. Moreover, EDDS-Co2+-Silica showed better degradation effects on MG than EDDS-Silica. Quantitative calculations based on density functional theory were used to predict the optimal coordination forms between Co2+and EDDS-Silica as well as the MG structure. The lowest unoccupied and highest occupied molecular orbitals of the catalysts were then used to predict the active sites on which MG tends to capture or release electrons during the degradation reaction. The optimal conditions for the synergistic removal of MG and Cr(Ⅵ) from a binary system using EDDS-Co2+-Silica were further investigated under different influencing factors. The results showed that EDDS-Co2+-Silica still had excellent catalytic effect on the degradation rate of MG in the range of pH 3-7, and the optimal conditions were as follows: solution pH, 7; degradation time, 1 h; temperature, 25 ℃; H2O2 concentration, 20 mmol/L; and the initial mass concentration of Cr(Ⅵ), 25 mg/L. Under the above conditions, the degradation rate was increased from 87.25% to 96.67% compared with that in the MG monosystem. Obvious enhancements in degradation effect and efficiency confirmed that the incorporation of EDDS-Co2+-Silica was favorable for the synergistic removal of MG and Cr(Ⅵ) in the binary system. Strongly oxidizing Cr(Ⅵ) can participate in the Fenton reaction, thus promoting MG degradation over a wide pH range. Thus, a positive synergistic effect exists between MG and Cr(Ⅵ). Considering that a large number of metal ions remained in the solution after the degradation reaction, EDDS-Silica was added to the degradation solution, and adsorption experiments were performed for 4 h at 30 ℃to adsorb and remove Cr and Fe via the strong chelating property of EDDS. The total residual mass concentrations of Cr and Fe were 4.96 and 1.02 mg/L, respectively, which meet national emission standards. These findings indicate that EDDS-Silica has good effects on the removal of residual metal ions after the nonhomogeneous Fenton reaction. As heterogeneous Fenton-like catalysts, the aminopolycarboxylic acid-modified materials proposed in this study can simultaneously promote the Fenton reaction and remove residual metal ions, thereby effectively removing MG and Cr(Ⅵ) from the binary system while ensuring that the content of residual metal ions in the system meets environmental emission standards. This study has broad application prospects in dye degradation and heavy-metal-ion wastewater treatment, and provides a reference value and theoretical basis for the development of other similar ligand-modified materials.

Highly efficient malachite green adsorption by bacterial cellulose and bacterial cellulose/locust bean gum composite.

In this study, bacterial cellulose (BC) and BC/locust bean gum (LBG) composite produced from banana hydrolysate were both used as the adsorbent for various organic dyes adsorption especially for malachite green (MG) adsorption for the first time. The BC/LBG(2%) composite exhibited significantly enhanced swelling rate and textural characteristics while maintained the basic structure of BC as depicted by XRD, FT-IR, and NMR, providing a foundation for its application as an excellent adsorbent. The composite exhibited a high adsorption rate and adsorption capacity for MG (exceeding 95 % and 2000 mg/g), and had a good selectivity for MG adsorption in the solution containing crystal violet (CV), rhodamine B (RB), and methyl orange (MO). The MG adsorption process conformed to multiple models including Langmuir and pseudo-first-order models. And the adsorption mechanism mainly comprised chemical adsorption (hydrogen bonding and electrostatic interactions) and physical adsorption. The reusability of BC/LBG(2%) composite was attractive for industrial application that the MG adsorption rate reduced merely a little (still higher than 88 %) after the 5th regeneration process. Overall, considering its adsorption capacity, selectivity, and reusability, BC/LBG(2%) composite prepared by in-situ fermentation with LBG addition was a competent adsorbent for MG adsorption and MG containing wastewater treatment.

Simultaneous removal of malachite green and lead from water by consortium dry-biomasses of Bacillus licheniformis AG3 and Bacillus cereus M116.

Synthetic textile dye malachite green (MG) and heavy metals present in industrial wastewater are hazardous to the ecosystem. Bioremediation of dyes and heavy metals using dry-biomasses has advantages over chemical methods. This study screened an acclimatized, heavy metal-resistant, and dye-degrading Gram positive Bacillus licheniformis AG3 strain from the textile wastewater near Kolkata, West Bengal. The EDXRF analysis of this colored wastewater effluent showed 36.33 mg/L lead, significantly higher than the WHO recommendation. Previously, Bag et al. showed bioremediation of synthetic dyes using dry-biomass of Bacillus cereus M116 from an aqueous solution (Bag et al. Arch Microbiol 203(7):3811-3823, 2021). Here, a consortium of dry-biomasses of B. licheniformis AG3 and B. cereus M116 strains (1:1 w/w ratio) was prepared for the simultaneous removal of lead and MG from wastewater. Statistical optimization determines that the pH, initial concentration of contaminants, and dry-biomass concentrations are critical for bioremediation under batch procedures. Further, optimization using the response surface methodology showed that 0.01% consortium dry-biomasses eliminated a maximum of 99.35% MG and 96.01% lead (II) within 6 h. SEM-EDS and FTIR confirmed a strong surface biosorption. Furthermore, a fixed-bed biofilter column of the consortium dry-biomasses was prepared, which was able to remove 98.1% MG and 98.5% lead at the 0.5-1 mL/min flow rate. Together, this study developed a biofilter with a consortium dry biomasses of B. licheniformis AG3 and B. cereus M116 for the simultaneous removal of MG and lead from wastewater.

Shining light on environmental remediation: a type-II heterojunction MnFe2O4/rGO nanocomposites for enhanced photocatalytic degradation of organic dyes and bisphenol A.

In this study, the pressing issue of persistent organic pollutants in wastewater was addressed by designing and fabricating a magnetically separable MnFe2O4/rGO heterostructure catalyst for efficient mineralization of bisphenol A (BPA) and dyes such as alizarin red S (anionic) and malachite green (cationic), which are known for their resistance to biodegradation and carcinogenic properties. Comprehensive structural and surface analyses using XRD, XPS, SEM, and TEM/HRTEM coupled with magnetic and optical property measurements revealed the formation of the MnFe2O4/rGO heterostructures. Among all, the MnFe2O4/rGO-10 catalyst with 10% wt% of rGO exhibited 100% efficiency in the mineralization of BPA and both dyes under visible light illumination within 60 min. The stability and recyclability of the catalyst, assessed through XRD and VSM studies, demonstrated its consistent performance over multiple uses. The cost-effectiveness and stability of this catalyst underscore its potential for practical application in wastewater treatment, offering a viable solution to the persistent challenge of removing stubborn organic contaminants.

Efficient degradation of emerging pollutant-malachite green in water by pulsed discharge plasma on water surface in cooperation with Fe2+/PMS.

The effective and rapid treatment of emerging pollutants in water is an essential solution to the pollution of water environment. The emerging pollutant-malachite green (MG) wastewater was treated using pulsed discharge plasma on water surface system (WSP) combining Fe2+/PMS. Compared with WSP alone, the addition of 125 µM Fe2+ and 0.5 mM peroxymonosulfate (PMS) in WSP could enhance the degradation efficiency and energy efficiency of MG by 32.8% and 9.7% respectively, with the synergistic factor of up to 2.056. UV-Vis absorption spectra and mineralization further demonstrated the synergistic effect. When the peak voltage and air flow rate were 22 kV and 0.7 L/min, the degradation efficiency and kinetic constant of MG could reach 97.9% and 0.259 min-1, respectively. MG degradation with high conductivity (1000 µS/cm) by WSP + Fe2+/PMS not only exhibited the better purification effect, but also could maintain the faster reaction rate. The active species involved in the degradation of MG in WSP + Fe2+/PMS system were mainly ·OH, SO4·-, O2·- and e*-. Furthermore, H2O2 and O3 also have a certain oxidizing effect on MG. Cl-, SO42-, HCO3- and humic acid (HA) could inhibit MG degradation to some extent, but still removed more than 80% of MG in water. The WSP + Fe2+/PMS reaction system was suitable for the treatment of other emerging pollutants in water. The results of LC-MS analysis revealed that the N-demethylation reaction and decomposition of conjugated structure were the important pathways for MG degradation. The H2O2 and acidic liquid environment provided by WSP laid the foundation for the formation of Fenton, and the introduced Fe2+ could fully undergo the Fenton and activation reaction with H2O2 and a small amount of PMS in the liquid phase, which enhanced the generation of active species, especially ·OH.

Direct detection of stringent alarmones (pp)pGpp using malachite green.

The alarmone (p)ppGpp serves as the signalling molecule for the bacterial universal stringent response and plays a crucial role in bacterial virulence, persistence, and stress adaptation. Consequently, there is a significant focus on developing new drugs that target and modulate the levels of (p)ppGpp as a potential strategy for controlling bacterial infections. However, despite the availability of various methods for detecting (p)ppGpp, a simple and straightforward detection method is needed. In this study, we demonstrated that malachite green, a well-established compound used for phosphate detection, can directly detect (p)ppGpp and its analogues esp., pGpp. By utilizing malachite green, we identified three new inhibitors of the hydrolase activity of SpoT, one of the two RelA-SpoT homolog (RSH) proteins responsible for making and hydrolyzing (p)ppGpp in Escherichia coli. These findings highlight the convenience and practicality of malachite green, which can be widely employed in high-throughput studies to investigate (pp)pGpp in vitro and discover novel regulators of RSH proteins.

New bacterial strains isolated from Tunisian biotopes: A sustainable enzymatic approach for decolorization and detoxification of Congo Red and Malachite Green.

Seven bacterial strains, isolated from various Tunisian biotopes, were investigated for Congo Red (CR) and Malachite Green (MG) decolorization. The isolated strains underwent morphological and biochemical tests, including assessments for antibiotic sensitivity as well as biofilm formation. One selected strain, ST11, was partially identified as Paenibacillus sp. strain ST11. The newly isolated crude bacterial filtrates (NICBFs) effectively decolorized CR and MG. Specifically, six and seven NICBFs were found to be effective for degrading CR (150 mg l-1) and MG (50 mg l-1), respectively. Under non-optimized conditions, CR and MG could be decolorized up to 80% within 6-12 h. The degradation products of CR and MG, characterized by UV-visible and FT-IR techniques, demonstrated both decolorization and transformation, highlighting the role of enzymes in dye degradation. Phytotoxicity and cytotoxicity studies evaluated the impact of treated and untreated CR and MG. Some NICBFs showed promise as powerful biological tools, reducing and sometimes detoxifying CR and MG, commonly used as fertilizers. The potential applications of these NICBFs in decolorization and bioremediation of dye-rich textile effluents were explored. The screening also identified environmentally friendly, cost-effective bacterial strains adaptable to various conditions through phytotoxicity and cytotoxicity studies.