Co(II) Substitution Enhances the Esterase Activity of a de Novo Designed Zn(II) Carbonic Anhydrase

Carbonic Anhydrases (CAs) have been a target for de novo protein designers due to the simplicity of the active site and rapid rate of the reaction. The first reported mimic contained a Zn(II) bound to three histidine imidazole nitrogens and an exogenous water molecule, hence closely mimicking the native enzymes' first coordination sphere. Co(II) has served as an alternative metal to interrogate CAs due to its d7 electronic configuration for more detailed solution characterization. We present here the Co(II) substituted [Co(II)(H2O/OH-)]N(TRIL2WL23H)3 n+ that behaves similarly to native Co(II) substituted human-CAs. Like the Zn(II) analogue, the cobalt-derivative at slightly basic pH is incapable of hydrolyzing p-nitrophenylacetate (pNPA); however, as the pH is increased a significant activity develops, which at pH values above 10 eventually yields a catalytic efficiency that exceeds that of the [Zn(II)(OH-)]N(TRIL2WL23H)3 + peptide complex. X-ray absorption analysis is consistent with an octahedral species at pH 7.5 that converts to a 5-coordinate species by pH 11. UV-vis spectroscopy can monitor this transition, giving a pKa for the conversion of 10.3. We assign this conversion to the formation of a 5-coordinate Co(II)(Nimid)3(OH)(H2O) species. The pH dependent kinetic analysis indicates the maximal rate (kcat), and thus the catalytic efficiency (kcat/Km), follow the same pH profile as the spectroscopic conversion to the pentacoordinate species. This correlation suggests that the chemically irreversible ester hydrolysis corresponds to the rate determining process.

Novel, Biosynthesis of Palladium Nanoparticles using Strychnos Potatorum Polysaccharide as a Green sustainable approach; and their effective Catalytic Hydrogenation of 4-Nitrophenol

In the current study, we successfully used strychnos potatorum polysaccharide through autoclaving to synthesize palladium nanoparticles in a green, sustainable process. These polysaccharide act as a stabilizing, capping, and reducing agent. It also used various analytical characterizations, including UV-Visible spectroscopy, FT-IR spectroscopy, X-Ray diffraction (XRD), Scanning electron microscopy (FE-SEM), EDAX, and X-ray photoelectron spectroscopy (XPS), TEM and gel permeation chromatography (GPC) are used to analyze biosynthesized pallidum nanoparticles (PdNPs). The surface plasmon resonance (SPR) band at 276 nm and UV-visible spectroscopy revealed the presence of the generated PdNPs. The XRD data show that PdNPs have crystalline behavior and a pristine face-centered cubic (FCC) structure. The PdNPs were successfully developed by catalytic reduction of 4-nitrophenol (4-NP). The catalytic activity and reusability of the environmentally friendly PdNPs catalyst were demonstrated by achieving a remarkable transformation of 95 % nitrophenol to 4-aminophenol after five cycles. The reaction rate constant (k) for the degradation of 4-nitrophenol (4-NP) using SP-PdNPs as a catalyst is 0.1201 min-1 and R2 0.9867, with a normalized rate constant of (Knor = K/m) of 7.206 s-1 mM-1. These findings provide fundamental knowledge of the catalytic process governing the hydrogenation of p-nitrophenol, which will help designers of effective catalysts. An innovative and affordable technique for creating PdNPs that are environmentally acceptable and can be utilized as effective catalysts in environmental applications is the use of strychnos potatorum gum polysaccharide. The green-synthesized PdNPs can be used for pollutant remediation, including pharmaceutical, domestic, heavy metal, industrial, and pesticide pollutants.

Incorporation of g-C3N4 nanosheets and CuO nanoparticles on polyester fabric for the dip-catalytic reduction of 4 nitrophenol

In the present work, we present the preparation of a new emerged heterogeneous catalyst (PE/g-C3N4/CuO) by in situ deposition of copper oxide nanoparticles (CuO) over the graphitic carbon nitride (g-C3N4) as the active catalyst and polyester (PE) fabric as the inert support. The synthesized sample (PE/g-C3N4/CuO) "dip catalyst" was studied by using various analytical techniques (Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy and dispersive X-ray spectroscopy (SEM/EDX), and transmission electron microscopy (TEM). The nanocomposite is utilized as heterogeneous catalysts for the 4-nitrophenol reduction in the presence of NaBH4, in aqueous solutions. According to experimental results, PE/g-C3N4/CuO with a surface of 6 cm2 (3 cm × 2 cm) demonstrated the catalyst exhibit excellent catalytic activity with 95% reduction efficiency for only 4 min of reaction and an apparent reaction rate constant (Kapp) of 0.8027 min-1. Further evidence that this catalyst based on prepared PE support can be a good contender for long-lasting chemical catalysis comes from the remarkable stability after 10 repetitions reaction cycles without a noticeably loss in catalytic activity. The novelty of this work consists to fabricate of catalyst based of CuO nanoparticles stabilized with g-C3N4 on the surface of an inert substrate PE, which results in an heterogenous dip-catalyst that can be easily introduced and isolated from the reaction solution with good retention of high catalytic performance in the reduction of 4-nitrophenol.

Carbonized wood impregnated with bimetallic nanoparticles as a monolithic continuous-flow microreactor for the reduction of 4-nitrophenol

Porous monolithic microreactors show great promise in catalytic applications, but are usually based on non-renewable materials. Herein, we demonstrate a Ni/Au nanoparticle-decorated carbonized wood (Ni/Au-CW) monolithic membrane microreactor for the efficient reduction of 4-nitrophenol. The hierarchical porous wood structure supports uniformly distributed heterobimetallic Ni/Au nanoparticles. As a consequence of these two factors, both mass diffusion and electron transfer are enhanced, resulting in a superior reduction efficiency of 99.5% as the liquor flows through the optimised Ni/Au-CW membrane. The reaction mechanism was investigated by electron paramagnetic resonance spectroscopy and density functional theory calculations. The proposed attraction-repulsion mechanism facilitated by the bimetallic nanoparticles has been ascribed to the different electronegativities of Ni and Au. The Ni/Au-CW membrane exhibits excellent catalytic performance and could be applicable to other catalytic transformations.

Concave gold nano-arrows (AuCNAs) for efficient catalytic reduction of 4-nitrophenol

Anisotropic gold nanostructures have attracted great attention in different fields including catalysis. Thermodynamically driven selective surface growth offers a reliable and reproducible method for anisotropic gold nanoparticle synthesis with specific morphologies. Herein, monocrystalline concave gold nano-arrows (AuCNAs) are prepared by the over-growth method using Au nanorods (AuNRs) as seeds. The as-prepared AuCNAs consist of a biconical head and four concave structures. Interestingly, silver ions (Ag⁺) concentration significantly affects the product morphology by tuning the peak positions of surface plasmon resonance (SPR), aspect ratio, arrow, and concave morphology of AuCNAs. The position of longitudinal SPR peaks is observed at 810, 805 and 782 nm at [Ag⁺]/[Au³⁺] molar ratios of 1:2, 1:1, and 2:1, respectively. Diameters and lengths of AuCNAs varied from 25 nm to 36 nm; 104 nm, 78 nm, and 120 nm, respectively. Additionally, the AuCNAs are applied for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of excess NaBH₄. Compared to gold nanorods (AuNRs), the prepared AuCNAs catalyst shows excellent catalytic activity, demonstrating that concave structures and sharp corners significantly enhance the catalytic activity. The value of pseudo-first-order reaction kinetic constants (k_app) increased from 0.0051 to 0.0195 s^-1 with increasing catalyst valume from 7.5 to 37.5 μL. The highest normalized reaction rate constant (K_nor) and turnover frequency (TOF) reach 5.84 × 10⁴ min^-1 mmol^-1 and 443.47 h^-1, respectively, at [Ag⁺]/[Au³⁺] ratio of 1:1 in AuCNAs catalyst. This study expands catalytic applications of anisotropic gold nanostructures and widens their potential application areas, such as surface plasmon exciton photonics, biomedical photonics, and photocatalysis.

p-Nitrophenol contaminated soil remediation in a spray-type coaxial cylindrical dielectric barrier discharge plasma system

In the present work, plasma remediation of p-nitrophenol (PNP) contaminated soil was performed in a novel spray-type coaxial cylindrical dielectric barrier discharge (DBD) system at ambient temperature. This system is capable of generating large-size nonthermal plasma (NTP) and improving the diffusion and transfer of chemical active species around the dispersed soil particles. Several key parameters including plasma treatment time, discharge voltage, soil granular size, the entry speed of soil, PNP initial concentration, gas variety, and gas flow rate were investigated in terms of PNP degradation and energy efficiencies. Under the optimized experimental conditions, 54.2% of PNP was degraded after only 50 s discharge treatment, indicating that the spray-type coaxial cylindrical DBD system can degrade organic pollutants in soil more quickly compared to other plasma systems due to its efficient transfer of reactive oxygen and nitrogen species (RONS) into the contaminated soil. The possible PNP degradation pathways were proposed based on intermediates identification results and the role of reactive species analysis. The toxicological assessment of the PNP decomposition products was conducted by quantitative structure-activity relationship (QASR) analysis. This work is expected to provide a potential plasma technology for rapid and efficient processing of industrial organic pollutants contamination soil.

3-D porous cellulose nanofibril aerogels with a controllable copper nanoparticle loading as a highly efficient non-noble-metal catalyst for 4-nitrophenol reduction

Nitrophenols(NPs) are highly toxic compounds that occur in various industrial effluents. Herein, we investigated Cu nanoparticle-loaded cellulose nanofibril (CNF/PEI-Cu) aerogels as a catalyst for degrading 4-nitrophenol (4NP) in the wastewater. Non-noble metal based low-cost catalyst material and easily scalable preparation method make CNF/PEI-Cu aerogel as an appropriate catalyst for practical application in 4NP wastewater treatment. Our strategy to improve the loading amount of homogeneously distributed Cu nanoparticles was to functionalize a CNF aerogel using polyethylene imine (PEI), which can bind Cu²⁺ ions. Porous CNF aerogels with homogenously distributed 20-40 nm Cu nanoparticles were obtained by adsorbing Cu²⁺ ions and chemically reducing them to Cu metal. The FTIR, XRD, SEM, XPS and ICP-OES analysis were used to confirm the in-situ formation of Cu nanoparticles. In the presence of the CNF/PEI-Cu aerogels, 4NP was effectively reduced to 4-aminophenol (4AP) without loss of the Cu nanoparticles. The activation energy (E_a) and reaction rate constant (k_app) of the catalytic 4NP reduction reaction by the CNF/PEI2-Cu aerogels were calculated to be E_a = 39.56 kJ mol^-1 and k_app = 0.770 min^-1, respectively. The E_a is similar or even smaller than the E_a values of the corresponding reactions involving noble-metal catalysts, demonstrating that the CNF/PEI-Cu aerogels developed in the present study have strong potential as practical and economical catalysts.

Swift reduction of nitroaromatics by gold nanoparticles anchored on steam-activated carbon black via simple preparation

Gold (Au) nanoparticles supported on certain platforms display highly efficient activity on nitroaromatics reduction. In this study, steam-activated carbon black (SCB) was used as a platform to fabricate Au/SCB composites via a green and simple method for 4-nitrophenol (4-NP) reduction. The obtained Au/SCB composites exhibit efficient catalytic performance in reduction of 4-NP (rate constant k_app = 2.1925 min^-1). The effects of SCB activated under different steam temperature, Au loading amount, pH, and reaction temperature and NaBH₄ concentration were studied. The structural advantages of SCB as a platform were analyzed by various characterizations. Especially, the result of N₂ adsorption-desorption method showed that steam activating process could bring higher surface area (from 185.9689 to 249.0053 m²/g), larger pore volume (from 0.073268 to 0.165246 cm³/g), and more micropore for SCB when compared with initial CB, demonstrating the suitable of SCB for Au NP anchoring, thus promoting the catalytic activity. This work contributes to the fabrication of other supported metal nanoparticle catalysts for preparing different functional nanocomposites for different applications.

Synthesis of dihydropyrimidine stabilized silver nanoparticles with significant anti urease and catalytic applications

We synthesized and explored biological and environmental applications of novel silver nanoparticles (AgNps) stabilized by short chain heterocyclic thiol namely Ethyl 6-methyl-4-phenyl-2-thioxo1,2,3,4-dihydropyrim-idine-5-carboxylate (DHPM). Dihydropyrimidines (DHPM), a biological active class of compounds that contain a single thiol group at the focal point which strongly stabilized the nascent AgNps. The short alkyl chain of (DHPM) effectively controlled the growth kinetics and surface morphology of AgNps. The synthesized Dihydropyrimidine stabilized silver nanoparticles (DHPM-AgNps) were investigated using Ultraviolet- visible spectroscopy (UV-Vis), Atomic force Microscopy (AFM) and Fourier-transform infrared spectroscopy (FTIR). AFM exhibited the size and shape of the DHPM-AgNps with an average diameter of 10 ± 1 nm. Our prepared DHPM-AgNps were examined for urease enzyme inhibition activity. The synthesized DHPM-AgNps showed significant level of urease inhibition activity (% of inhibition 40.3±0.28%) when compared with standard thiourea inhibition activity (% of inhibition value 79.6± 0.47%.). Moreover prepared DHPM-AgNps system successfully applied for the reduction of para-nitrophenol (p-Nip). It reduces the para-nitrophenol (p-Nip) to para-aminophenol (p-Amp) within one second in the presence of NaBH₄ under ambient temperature and pressure conditions, which followed the pseudo-first-order rate kinetics. This study will provide useful guidelines for designing efficient catalysts and stabilizing agents for Silver Nanoparticles.

Promoting Oral Mucosal Wound Healing with a Hydrogel Adhesive Based on a Phototriggered S-Nitrosylation Coupling Reaction

The wet and highly dynamic environment of the mouth makes local treatment of oral mucosal diseases challenging. To overcome this, a photo-crosslinking hydrogel adhesive is developed inspired by the success of light-curing techniques in dentistry. The adhesive operates on a fast (within 5 s) phototriggered S-nitrosylation coupling reaction and employs imine anchoring to connect to host tissues. Unlike other often-used clinical agents that adhere weakly and for short durations, this thin, elastic, adhesive, and degradable cyclic o-nitrobenzyl-modified hyaluronic acid gel protects mucosal wounds from disturbance by liquid rinsing, oral movement, and friction for more than 24 h. The results from both rat and pig oral mucosa repair models demonstrate that this new gel adhesive creates a favorable microenvironment for tissue repair and can shorten tissue healing time. This study thus illustrates a therapeutic strategy with the potential to advance the treatment of oral mucosal defects in the clinic.

Single-cell analysis of regions of interest (SCARI) using a photosensitive tag

The functional activity and differentiation potential of cells are determined by their interactions with surrounding cells. Approaches that allow unbiased characterization of cell states while at the same time providing spatial information are of major value to assess this environmental influence. However, most current techniques are hampered by a tradeoff between spatial resolution and cell profiling depth. Here, we develop a photocage-based technology that allows isolation and in-depth analysis of live cells from regions of interest in complex ex vivo systems, including primary human tissues. The use of a highly sensitive 4-nitrophenyl(benzofuran) cage coupled to a set of nanobodies allows high-resolution photo-uncaging of different cell types in areas of interest. Single-cell RNA-sequencing of spatially defined CD8+ T cells is used to exemplify the feasibility of identifying location-dependent cell states. The technology described here provides a valuable tool for the analysis of spatially defined cells in diverse biological systems, including clinical samples.

Mussel-Inspired Ag NPs Immobilized on Melamine Sponge for Reduction of 4-Nitrophenol, Antibacterial Applications and Its Superhydrophobic Derivative for Oil-Water Separation

A functional material integrated with a variety of functions is highly desired in wastewater treatment. In this research, a mussel-inspired method of immobilizing silver nanoparticles on the skeleton of a melamine sponge is proposed and applied for water remediation. Ag NPs were reduced in situ and grown on a polydopamine-modified melamine sponge. The catalytic reduction of 4-nitrophenol (4-NP) in the presence of the obtained MS-PDA-Ag was evaluated, and the results demonstrated that the MS-PDA-Ag presented high catalytic reduction activity. In addition, the monolithic MS-PDA-Ag presents excellent reusability with no remarkable decrease in catalytic efficiency after multiple reuses. Owing to the immobilized Ag NPs, the MS-PDA-Ag can also effectively inhibit the growth of bacteria against both gram-positive and gram-negative species, making it possible for bacteria elimination in polluted water. To further explore the possibility of utilizing the MS-PDA-Ag for versatile applications, a superhydrophobic derivative (S-MS-PDA-Ag) was prepared by coating a low-surface-energy substance (octadecanethiol) on the surface of MS-PDA-Ag. The obtained S-MS-PDA-Ag presents the capacities of oil/organics adsorption and water repellence, which can separate the insoluble oil/organics from water. The melamine sponge immobilized with Ag NPs demonstrates prominent catalytic reduction of 4-NP, antibacterial activity and the superhydrophobic derivative presents the capacity of insoluble oil/organics separation from oil-water mixtures, exhibiting high potential in the remediation of polluted water.

Esterase Activity of Serum Albumin Studied by 1H NMR Spectroscopy and Molecular Modelling

Serum albumin possesses esterase and pseudo-esterase activities towards a number of endogenous and exogenous substrates, but the mechanism of interaction of various esters and other compounds with albumin is still unclear. In the present study, proton nuclear magnetic resonance (1H NMR) has been applied to the study of true esterase activity of albumin, using the example of bovine serum albumin (BSA) and p-nitrophenyl acetate (NPA). The site of BSA esterase activity was then determined using molecular modelling methods. According to the data obtained, the accumulation of acetate in the presence of BSA in the reaction mixture is much more intense as compared with the spontaneous hydrolysis of NPA, which indicates true esterase activity of albumin towards NPA. Similar results were obtained for p-nitophenyl propionate (NPP) as substrate. The rate of acetate and propionate release confirms the assumption that there is a site of true esterase activity in the albumin molecule, which is different from the site of the pseudo-esterase activity Sudlow II. The results of molecular modelling of BSA and NPA interaction make it possible to postulate that Sudlow site I is the site of true esterase activity of albumin.

Solar-Powered Whole-Cell P450 Catalytic Platform for C-Hydroxylation Reactions

Invited for this month's cover is the joint research group of Prof. Chan Beum Park at the Korea Advanced Institute of Science and Technology (KAIST) and Prof. Chul-Ho Yun at the Chonnam National University (CNU). The image shows how the use of a natural photosensitizer, flavin mononucleotide, and visible light can lead to a cost-effective, green, and sustainable process for P450-catalyzed reactions in a whole-cell system. The Communication itself is available at 10.1002/cssc.202100944.

Generation and characterization of a laforin nanobody inhibitor

OBJECTIVES

Mutations in the gene encoding the glycogen phosphatase laforin result in the fatal childhood dementia Lafora disease (LD). A cellular hallmark of LD is cytoplasmic, hyper-phosphorylated, glycogen-like aggregates called Lafora bodies (LBs) that form in nearly all tissues and drive disease progression. Additional tools are needed to define the cellular function of laforin, understand the pathological role of laforin in LD, and determine the role of glycogen phosphate in glycogen metabolism. In this work, we present the generation and characterization of laforin nanobodies, with one being a laforin inhibitor.

DESIGN AND METHODS

We identify multiple classes of specific laforin-binding nanobodies and determine their binding epitopes using hydrogen deuterium exchange (HDX) mass spectrometry. Using para-nitrophenyl phosphate (pNPP) and a malachite gold-based assay specific for glucan phosphatase activity, we assess the inhibitory effect of one nanobody on laforin's catalytic activity.

RESULTS

Six families of laforin nanobodies are characterized and their epitopes mapped. One nanobody is identified and characterized that serves as an inhibitor of laforin's phosphatase activity.

CONCLUSIONS

The six generated and characterized laforin nanobodies, with one being a laforin inhibitor, are an important set of tools that open new avenues to define unresolved glycogen metabolism questions.

Structure-Guided Development of Potent Benzoylurea Inhibitors of BCL-XL and BCL-2

The BCL-2 family of proteins (including the prosurvival proteins BCL-2, BCL-X_L, and MCL-1) is an important target for the development of novel anticancer therapeutics. Despite the challenges of targeting protein-protein interaction (PPI) interfaces with small molecules, a number of inhibitors (called BH3 mimetics) have entered the clinic and the BCL-2 inhibitor, ABT-199/venetoclax, is already proving transformative. For BCL-X_L, new validated chemical series are desirable. Here, we outline the crystallography-guided development of a structurally distinct series of BCL-X_L/BCL-2 inhibitors based on a benzoylurea scaffold, originally proposed as α-helix mimetics. We describe structure-guided exploration of a cryptic "p5" pocket identified in BCL-X_L. This work yields novel inhibitors with submicromolar binding, with marked selectivity toward BCL-X_L. Extension into the hydrophobic p2 pocket yielded the most potent inhibitor in the series, binding strongly to BCL-X_L and BCL-2 (nanomolar-range half-maximal inhibitory concentration (IC₅₀)) and displaying mechanism-based killing in cells engineered to depend on BCL-X_L for survival.

DNA-templated silver nanoclusters as an efficient catalyst for reduction of nitrobenzene derivatives: a systematic study

Nitrobenzene compounds are highly toxic pollutants with good stability, and they have a major negative impact on both human health and the ecological environment. Herein, it was found for the first time that fluorescent DNA-silver nanoclusters (DNA-AgNCs) can catalyze the reduction of toxic and harmful nitro compounds into less toxic amino compounds with excellent tolerance to high temperature and organic solvents. In this study, the reduction of p-nitrophenol (4-NP) as a model was systematically investigated, followed by expending the substrate to disclose the versatility of this reaction. This report not only expanded the conditions for utilizing catalytic reduction conditions of DNA-AgNCs as an efficient catalyst in the control of hazardous chemicals but also widened the substrate range of DNA-AgNCs reduction, providing a new angle for the application of noble metal nanoclusters.

Is PF-00835231 a Pan-SARS-CoV-2 Mpro Inhibitor? A Comparative Study

The COVID-19 outbreak continues to spread worldwide at a rapid rate. Currently, the absence of any effective antiviral treatment is the major concern for the global population. The reports of the occurrence of various point mutations within the important therapeutic target protein of SARS-CoV-2 has elevated the problem. The SARS-CoV-2 main protease (Mpro) is a major therapeutic target for new antiviral designs. In this study, the efficacy of PF-00835231 was investigated (a Mpro inhibitor under clinical trials) against the Mpro and their reported mutants. Various in silico approaches were used to investigate and compare the efficacy of PF-00835231 and five drugs previously documented to inhibit the Mpro. Our study shows that PF-00835231 is not only effective against the wild type but demonstrates a high affinity against the studied mutants as well.

Surface Permeability of Membrane and Catalytic Performance Based on Redox-Responsive of Hybrid Hollow Polymeric Microcapsules

"Smart" polymeric microcapsules with excellent permeability of membranes have drawn considerable attention in scientific and industrial research such as drug delivery carriers, microreactors, and artificial organelles. In this work, hybrid hollow polymeric microcapsules (HPs) containing redox-active gold-sulfide bond were prepared with bovine serum albumin, inorganic metal cluster (AuNCs), and poly(N-isopropylacrylamide) conjugates by using Pickering emulsion method. HPs were transferred from water-in-oil to water-in-water by adding PEGbis(N-succinimidylsuccinate). To achieve redox-responsive membrane, the Au-S bond units incorporated into the microcapsules' membranes, allowed us to explore the effects of a new stimuli, that is, the redox Au-S bond breaking on the microcapsules' membranes. The permeability of these hybrid hollow polymeric microcapsules could be sensitively tuned via adding environment-friendly hydrogen peroxide (H2O2), resulting from a fast fracture of Au-S bond. Meanwhile, AuNCs and conjugates could depart from the microcapsules, and enhance the permeability of the membrane. Based on the excellent permeability of the membrane, phosphatase was encapsuled into HPs and p-nitrophenyl phosphate as a substrate. After adding 1 × 10-2 and 1 × 10-4 M H2O2, the catalytic efficiency was nearly 4.06 and 2.22 times higher than that of HPs in the absence of H2O2, respectively. Hence, the unique redox-responsive HPs have potential applications in biocatalytic reaction, drug delivery, and materials as well as in bioscience.

Efficient recovery of palladium nanoparticles from industrial wastewater and their catalytic activity toward reduction of 4-nitrophenol

Discharge of heavy metals from various sources of industrial wastewater poses significant environmental and health concerns. Thus, efficient recovery of precious metals from wastewater employing sustainable, rapid, and cost-effective treatment methods is highly desirable. In this work, palladium nanoparticles (Pd NPs) were successfully recovered from industrial wastewater using a pulsed laser process in the absence of additives or reducing agents. Notably, the developed approach is faster and more environmentally friendly than other conventional recovery methods. The recovered Pd NPs were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Various pulsed laser parameters (i.e., laser wavelength, power, and irradiation time) were optimized to obtain ideal conditions for the pulsed laser ablation process. Effective recovery of the Pd metal from industrial wastewater was achieved at a laser wavelength of 355 nm, power of 40 mJ/pulse, and irradiation time of 30 min. The Pd NPs exhibited excellent catalytic activity toward the reduction of 4-nitrophenol. Thus, the recovered materials showed remarkable potential for application in degradation of toxic aromatic nitro compounds in the environment.

Single source precursor synthesized CuS nanoparticles for NIR phototherapy of cancer and photodegradation of organic carcinogen

Herein, we report cost effective and body compatible CuS nanoparticles (NPs) derived from a single source precursor as photothermal agent for healing deep cancer and photocatalytic remediation of organic carcinogens. These NPs efficiently kill MCF7 cells (both in vivo and in vitro) under NIR irradiation by raising the temperature of tumor cells. Such materials can be used for the treatment of deep cancer as they can produce a heating effect using high wavelength and deeply penetrating NIR radiation. Furthermore, CuS NPs under solar light irradiation efficiently convert p-nitrophenol (PNP), an environmental carcinogen, to p-aminophenol (PAP) of pharmaceutical implication. In a nutshell, CuS can be used for the treatment of deep cancer and for the remediation of carcinogenic pollutants. There seems an intrinsic connection between the two functions of CuS NPs that need to be explored in length.

Strategy to improve gold nanoparticles loading efficiency on defect-free high silica ZSM-5 zeolite for the reduction of nitrophenols

Catalytic reduction of toxic and aqueous stable nitrophenols by gold nanoparticles (Au NPs) is hot issue due to the serious environmental pollution in recent years. But the expensive price and poor recycling performance of Au NPs limit its further application. Defect-free high silica zeolite is suitable support for Au NPs due to its cheaper price, higher stability and stronger adsorbability, but the low alumina content and defect sites usually lead to poor Au NPs loading efficiency. Herein, we reported the improved Au NPs loading efficiency on defect-free high silica ZSM-5 zeolite through the additional surface fluffy structure. The fluffy structure was created through the addition of multi-walled carbon nanotubes (MWCNTs) and ethanol into synthesis gel. Highly dispersed ca. 4 nm Au NPs on zeolite surface are prepared by the green enhanced sol-gel immobilization method. The Au NPs loading efficiency on conventional ZSM-5 zeolite is 10.7%, in contrast, this result can arrive to 82.6% on fluffy structure ZSM-5 zeolite. The fluffy structure ZSM-5 zeolite and Au NPs nanocomposites show higher efficiency than traditional Au/ZSM-5 nanocomposites towards catalytic reduction of nitrophenols. Additionally, the experiments with different affecting factors (MWCNTs dosage, aging time, catalysts dosage, pH, initial 4-NP concentration, storage time and recycling times) were carried out to test general applicability of the nanocomposites. And the degradation of nitrophenols experiment was operated to explore the catalytic performance of the prepared nanocomposites in further environmental application. The detailed possible relationship between zeolite with fluffy structure and Au NPs is also proposed in the paper.

New insights into the reinforced reduction performance of Fe0/C internal electrolysis activated by persulfate for p-nitrophenol removal

In this study, the reduction of iron-carbon internal electrolysis was reinforced by persulfate for p-nitrophenol removal. The effects of persulfate dosage, initial pH and iron-carbon mass ratio were comprehensively studied in batch experiments. In the system of iron-carbon internal electrolysis coupled with persulfate, the iron-carbon internal electrolysis and persulfate had a significant mutual influence, exhibiting a wide range of pH in the treatment process. Moreover, the coupled system also showed the remarkable removal and degradation efficiency of p-nitrophenol according to the contrast experiments. The satisfactory results should be attributed to the potential reduction of iron-carbon internal electrolysis, which was stimulated by persulfate to transform the nitro group to the amine group, accompanying the subsequent oxidation. Furthermore, persulfate possessed the ability that the dynamically destructive effect on external and internal of Fe⁰ and the scavenging action on activated carbon, effectively strengthening the potential energy for release and transfer of reductive substances. Both HO^• and SO₄^•- as the main free radicals were formed to mineralize the intermediates in the coupled system. These findings indicate that the system of iron-carbon internal electrolysis coupled with persulfate can be a promising strategy for the treatment of the toxic and refractory wastewater.

Controlling the Kinetics of an Enzymatic Reaction through Enzyme or Substrate Confinement into Lipid Mesophases with Tunable Structural Parameters

Lipid liquid crystalline mesophases, resulting from the self-assembly of polymorphic lipids in water, have been widely explored as biocompatible drug delivery systems. In this respect, non-lamellar structures are particularly attractive: they are characterized by complex 3D architectures, with the coexistence of hydrophobic and hydrophilic regions that can conveniently host drugs of different polarities. The fine tunability of the structural parameters is nontrivial, but of paramount relevance, in order to control the diffusive properties of encapsulated active principles and, ultimately, their pharmacokinetics and release. In this work, we investigate the reaction kinetics of p-nitrophenyl phosphate conversion into p-nitrophenol, catalysed by the enzyme Alkaline Phosphatase, upon alternative confinement of the substrate and of the enzyme into liquid crystalline mesophases of phytantriol/H₂O containing variable amounts of an additive, sucrose stearate, able to swell the mesophase. A structural investigation through Small-Angle X-ray Scattering, revealed the possibility to finely control the structure/size of the mesophases with the amount of the included additive. A UV-vis spectroscopy study highlighted that the enzymatic reaction kinetics could be controlled by tuning the structural parameters of the mesophase, opening new perspectives for the exploitation of non-lamellar mesophases for confinement and controlled release of therapeutics.

Polymersome-Based Modular Nanoreactors with Size-Selective Transmembrane Permeability

Polymersome nanoreactors encapsulating the enzymes or particulate catalysts attract interest because of their potential use as modular reactors to synthesize complex compounds via a cascade of chemical reactions in a single batch. To achieve these goals, a key requirement is the tunable permeability of the polymersome membrane, which allows the size-selective transportation of reagents and products while protecting the encapsulated catalysts during the chemical reaction. We report here a stimuli-responsive route for controlling the permeability of the polymersomes of the binary blend of poly(ethylene glycol)-b-polystyrene (PEG-b-PS) and poly(ethylene glycol)-b-poly(acrylbenzylborate) (PEG-b-PABB). The presence of H₂O₂ (1 mM) in the medium (0.1 M PBS, pH 7.4) triggers the oxidation of benzyl borate pendants of PABB to form poly(acrylic acid) (PAA). This transformation results in the perforation of the compartmentalizing membrane of polymersomes by the dissolution of PEG-b-PAA domains embedded in the inert PEG-b-PS matrix. By controlling the composition of the stimuli-responsive block copolymer, the polymersomes of the binary blend exhibit size-selective permeability without losing the structural integrity. Release of fluorescent guests with different sizes (fluorescein, PEG2k-Cm, PEG5k-Rho) can be controlled by tuning the composition (PEG-b-PS/PEG-b-PABB = 100/0-80/20) of blended polymersomes. Selective permeability of the membrane provides protection of the encapsulated enzymes from external proteases present in the medium, resulting in the one-pot synthesis of small molecules via cascades of chemical reactions. The nanoparticular catalysts are also encapsulated within the permeable polymersomes, serving as modular reactors for the conversion of organic compounds via a cascade of reactions.

Theoretical insight into the degradation of p-nitrophenol by OH radicals synergized with other active oxidants in aqueous solution

The degradation of p-nitrophenol (p-NP) based on OH radicals (HO^∙), HO₂ radicals (HO₂^∙) and O₂ in aqueous solution was investigated using theoretical computational methods. The complete degradation mechanisms of reaction between p-NP and HO^∙ were explored by density functional theory (DFT) methods. The 4-nitrophenoxy radicals and 1,2-dihydroxy-4-nitrocylohexadienyl radicals are confirmed to be major intermediates of the HO^∙-initiated reactions in aqueous phase, which consistent with experimental results. The chemical structures of some products (2,4-dihydroxycyclohexa-2,4-dien-1-one and 4-nitrocyclohexa-3,5-diene-1,2-dione) which were not identified in the experiment are determined. New favorable formation channels for some intermediates were found. The primary reactions initiated by HO^∙ or HO₂^∙ with p-NP reveals that HO^∙-initiated degradation is the dominant reaction. HO₂^∙ and O₂ can enhance the degradation extent of p-NP in further reactions. Rate constants of the elementary reactions and overall rate constants were calculated. In addition, the HO^∙-initiated primary reactions in a water box of 500 water molecules were studied using Monte Carlo simulation. All the OH-addition reactions are barrierless and highly feasible. The observed dynamic reaction process is similar to the DFT calculation prediction. Furthermore, the eco-toxicity evaluation shows that important products are harmless or harmful to aquatic organisms, and are much less toxic than p-NP.

Carbon dots-inspired fluorescent cyclodextrins: competitive supramolecular "off-on" (bio)sensors

Chromophore-appended cyclodextrins combine the supramolecular loading capabilities of cyclodextrins (CDs) with the optical properties of the affixed chromophores. Among fluorescent materials, carbon dots (CNDs) are attractive and the feasibility of CND-appended CDs as sensors has been demonstrated by different authors. However, CNDs are intrinsically heterogeneous materials and their ulterior functionalization yields hybrid composites that are not well defined in terms of structure and composition. Inspired by the fluorescence properties of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA), the most paradigmatic of the molecular fluorophores detected in CNDs, herein we report two highly efficient synthetic chemical strategies for the preparation of IPCA-appended CDs that behave as CND-based CD "turn off-on" biosensors suitable for the analysis of cholesterol and β-galactosidase activity. We have deconstructed the CND-CD systems to demonstrate that (i) the role of CNDs is limited to acting as a support for the molecular fluorophores produced during their synthesis and (ii) the molecular fluorophores suffice for the determination of the enzymatic activity based on the quenching by p-nitrophenol as a sacrificial quencher.

Development of a Simple Reversible-Flow Method for Preparation of Micron-Size Chitosan-Cu(II) Catalyst Particles and Their Testing of Activity

A simple flow system employing a reversible-flow syringe pump was employed to synthesize uniform micron-size particles of chitosan-Cu(II) (CS-Cu(II)) catalyst. A solution of chitosan and Cu(II) salt was drawn into a holding coil via a 3-way switching valve and then slowly pumped to drip into an alkaline solution to form of hydrogel droplets. The droplets were washed and dried to obtain the catalyst particles. Manual addition into the alkaline solution or employment of flow system with a vibrating rod, through which the end of the flow line is inserted, was investigated for comparison. A sampling method was selected to obtain representative samples of the population of the synthesized particles for size measurement using optical microscopy. The mean sizes of the particles were 880 ± 70 µm, 780 ± 20 µm, and 180 ± 30 µm for the manual and flow methods, without and with the vibrating rod, respectively. Performance of the flow methods, in terms of rate of droplet production and particle size distribution, are discussed. Samples of 180 µm size CS-Cu(II) particles were tested for catalytic reduction of 0.5 mM p-nitrophenol to p-aminophenol by 100-fold excess borohydride. The conversion was 98% after 20 min, whereas without the catalyst there was only 14% conversion.

In-situ synthesis of metal nanoparticles@metal-organic frameworks: Highly effective catalytic performance and synergistic antimicrobial activity

M-NP@Zn-BIF (M-NP = Ag or Cu nanoparticle; Zn-BIF is a zinc-based boron imidazolate framework, Zn₂(BH(2-mim)₃)₂(obb); 2-mim = 2-methylimidazole; obb = 4,4'-oxybis(benzoate)) composites were successfully in-situ synthesized by utilizing the reducing ability of the BH bond contained in the Zn-BIF at room temperature without any additional chemical reduction reagents. These composites (225 μg/mL) exhibited excellent catalytic activity to convert 4-nitrophenol to 4-aminophenol in 2.5 min and 6 min with a conversion rate of 99.9 %, respectively. In addition, Ag@Zn-BIF (50 μg/mL) showed highly synergistic antibacterial activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with a bactericidal rate of approximately 99.9 %. An antibacterial mechanism was proposed for the generation of intracellular reactive oxygen species (ROS) levels. Superoxide radicals (O^2-) and hydroxyl radicals (OH) formed during the antibacterial process were shown to accelerate the death of bacteria. They also exhibited highly photocatalytic activity for Rhodamine B (RhB). When the concentration of the composites is 1000 μg/mL, the photocatalytic efficiency of Ag@Zn-BIF and Cu@Zn-BIF increased by 31.62 and 18.13 times compared with Zn-BIF, respectively. All in all, this study developed a simple and versatile integrated platform for the removal of nitrophenols, organic dyes, and the effective inactivation of bacteria in water.

Nanoparticle-Mediated Co-Delivery of Notch-1 Antibodies and ABT-737 as a Potent Treatment Strategy for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) accounts for nearly one-quarter of all breast cancer cases, but effective targeted therapies for this disease remain elusive because TNBC cells lack expression of the three most common receptors seen on other subtypes of breast cancer. Here, we exploit TNBC cells' overexpression of Notch-1 receptors and Bcl-2 anti-apoptotic proteins to provide an effective targeted therapy. Prior studies have shown that the small molecule drug ABT-737, which inhibits Bcl-2 to reinstate apoptotic signaling, is a promising candidate for TNBC therapy. However, ABT-737 is poorly soluble in aqueous conditions, and its orally bioavailable derivative causes severe thrombocytopenia. To enable targeted delivery of ABT-737 to TNBC and enhance its therapeutic efficacy, we encapsulated the drug in poly(lactic-co-glycolic acid) nanoparticles (NPs) that were functionalized with Notch-1 antibodies to produce N1-ABT-NPs. The antibodies in this NP platform enable both TNBC cell-specific binding and suppression of Notch signaling within TNBC cells by locking the Notch-1 receptors in a ligand unresponsive state. This Notch inhibition potentiates the effect of ABT-737 by up-regulating Noxa, resulting in effective killing of TNBC cells. We present the results of in vitro studies that demonstrate N1-ABT-NPs can preferentially bind TNBC cells versus noncancerous breast epithelial cells to effectively regulate Bcl-2 and Notch signaling to induce cell death. Further, we show that N1-ABT-NPs can accumulate in subcutaneous TNBC xenograft tumors in mice following systemic administration to reduce tumor burden and extend animal survival. Together, these findings demonstrate that NP-mediated co-delivery of Notch-1 antibodies and ABT-737 is a potent treatment strategy for TNBC that may improve patient outcomes with further development and implementation.

Synthesis of AgNPs coated with secondary metabolites of Acacia nilotica: An efficient antimicrobial and detoxification agent for environmental toxic organic pollutants

This study concentrates on biosynthesis of Silver Nanoparticles (AgNPs) from stem extract of Acacia nilotica (A. nilotica). The reaction was completed at a temperature ~40-45 °C and time duration of 5 h. AgNPs were thoroughly investigated via advanced characterization techniques such as UV-Vis spectrophotometry (UV-Vis), Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffractometry (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), X-ray Photoelectron Spectroscopy (XPS), Thermo Gravimetric Analysis (TGA), Diffuse Reflectance Spectroscopy (DRS), Brunner-Emmett-Teller (BET), Dynamic Light Scattering (DLS), and Zeta potential analysis. AgNPs with average size below 50 nm were revealed by all the measuring techniques. Maximum surface area ~5.69 m²/g was reported for the as synthesized NPs with total pore volume ~0.0191 mL/g and average pore size ~1.13 nm. Physical properties such as size and shape have changed the surface plasmon resonance peak in UV-visible spectrum. Antimicrobial activity was reported due to denaturation of microbial ribosome's sulphur and phosphorus bond by silver ions against bacterium Methicillin Resistant Staphylococcus aureus (MRSA) and fungus Candida Albican (CA). Furthermore, AgNPs degraded toxic pollutants such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP) and various hazardous dyes such as Congo Red (CR), Methylene Blue (MB) and Methyl Orange (MO) up to 95%. The present work provided low cost, green and an effective way for synthesis of AgNPs which were utilized as potential antimicrobial agents as well as effective catalyst for detoxification of various pollutants and dyes.

Platinum Nanoparticles Obtained at Mild Conditions on S-Layer Protein/Polymer Particle Supports

This work presents the synthesis of platinum nanoparticles supported on S-layer protein/polymeric particle systems, obtained by combining proteins isolated from Lactobacillus kefiri and an aqueous dispersion of acrylic particles. FTIR spectra of the protein/polymer supports did not show changes in the Amide I band of the proteins, suggesting that proteins maintained their conformation after adsorption. The SAXS spectra and DLS results are consistent with the formation of a protein corona around the polymer particles. After combining the supports with the platinum complex and subsequently reducing the combination with hydrogen at mild conditions, we obtained colloidal nanocomposite materials. In these, platinum nanoparticles with diameters around 3 nm located on the surface of the protein/polymer supports were observed by TEM. The obtained nanosystems showed catalytic activity in the reduction of p-nitrophenol with NaBH₄ at room temperature with conversions of 100% for reaction times of 50 to 70 min.

Catalytic degradation of p-nitrophenol by magnetically recoverable Fe3O4 as a persulfate activator under microwave irradiation

In this study, Fe₃O₄ and microwave (MW) were combined to activate persulfate (PS) for the removal of organic matter, resulting in the enhanced degradation of p-nitrophenol (PNP) in solution. During the preparation of Fe₃O₄, the effect of sodium acetate was examined, and the results showed that the concentration of sodium acetate had little effect on the catalytic activity of the Fe₃O₄/PS/MW system but did have an effect on the Fe₃O₄ yield. In addition, with regards to the representative environmental factors, the degradation experiment showed that humic acid and the co-existing anions of chloride, sulfate, nitrate, and phosphate had little effects on p-nitrophenol removal; however, carbonate had a negative effect. In addition, the Fe₃O₄/PS/MW system performed well in the initial pH range of 3.0-9.0. According to the quenching experiment and electron paramagnetic resonance (EPR) detection, sulfate radicals and a minority of hydroxyl radicals play dominant roles in the degradation process. In addition, the role of Fe₃O₄ was confirmed to take part in the degradation process by X-ray photoelectron spectroscopy (XPS) analysis. Because of the good performance observed in the water matrices of tap water and the Songhua River, these results demonstrate the potential application of the Fe₃O₄/PS/MW system for wastewater treatment.

Electrospun metal-organic frameworks with polyacrylonitrile as precursors to hierarchical porous carbon and composite nanofibers for adsorption and catalysis

A facile and effective method has been developed to prepare hierarchical porous carbon nanofibers (PCNFs), carbon nanofibers supported nickel nanoparticles (PCNFs-Ni) and carbon nanofibers encapsulating gold nanoparticles (PCNFs-Au). PCNFs or PCNFs-Au were obtained by embedding metal-organic frameworks (e.g. ZIF-8 or ZIF-8-Au) into polyacrylonitrile via electrospinning and subsequent carbonization. In addition, PCNFs-Ni were obtained by impregnating PAN/ZIF-8 nanofibers in Ni(NO₃)₂·6H₂O followed by carbonization. Both PCNF and PCNF-Ni exhibited excellent adsorption activities for methylene blue (MB) and congo red (CR). Especially, PCNF-Ni could be removed and separated via a magnet. PCNFs-Au showed excellent catalytic properties in the reduction reaction of 4-nitrophenol (4-NP).

Acoustic cavitation assisted destratified clay tactoid reinforced in situ elastomer-mimetic semi-IPN hydrogel for catalytic and bactericidal application

Ultrasonicaion is non-chemical process where acoustic waves have been targeted to aqueous medium dispersed precursor materials. In situ synthesis of silver nanoparticles anchored in hydrogel matrix has been opted via ~20 kHz frequency assisted (bath sonication) synthesis having the ultrasonication power intensity (UPI) of ~10⁶ J/m². Power intensity is inversely proportional to the surface area of the clay tactoids. The hydrogel have been prepared by in situ 20 kHz assisted sonochemical destratification of laponite clay tactoids which could be terminologically stated as 'top-down method'. Silver nanoparticles (AgNPs) have been deposited in the surfaces of the porous matrix of hydrogel via 'soak and irradiate' method. Soaking of silver ions into the gel matrix is welcomed due to their efficient stabilization and fast transformation towards AgNPs. AgNPs played the key role in catalytic reduction and bactericidal activity. Moreover, the prepared hydrogel has enough robust to withstand cyclic stress, uniaxial stress and oscillatory stress which have been extensively justified by the physico-mechanical characterizations. The gel supported catalyst showed first order reaction kinetics and less time consuming period during reduction of 4-nitrophenol as a model pollutant.

A Combined Mechanochemical and Calcination Route to Mixed Cobalt Oxides for the Selective Catalytic Reduction of Nitrophenols

Para-, or 4-nitrophenol, and related nitroaromatics are broadly used compounds in industrial processes and as a result are among the most common anthropogenic pollutants in aqueous industrial effluent; this requires development of practical remediation strategies. Their catalytic reduction to the less toxic and synthetically desirable aminophenols is one strategy. However, to date, the majority of work focuses on catalysts based on precisely tailored, and often noble metal-based nanoparticles. The cost of such systems hampers practical, larger scale application. We report a facile route to bulk cobalt oxide-based materials, via a combined mechanochemical and calcination approach. Vibratory ball milling of CoCl2(H2O)6 with KOH, and subsequent calcination afforded three cobalt oxide-based materials with different combinations of CoO(OH), Co(OH)2, and Co3O4 with different crystallite domains/sizes and surface areas; Co@100, Co@350 and Co@600 (Co@###; # = calcination temp). All three prove active for the catalytic reduction of 4-nitrophenol and related aminonitrophenols. In the case of 4-nitrophenol, Co@350 proved to be the most active catalyst, therein its retention of activity over prolonged exposure to air, moisture, and reducing environments, and applicability in flow processes is demonstrated.

Comparative time-based intermediates study of ozone oxidation of 4-chloro- and 4-nitrophenols followed by LCMS-TOF

Greater insights on the degradation pathways and intermediates formed during the oxidation of organics can be achieved by more suitable and compatible instrumentation. In our research, we sought to explore the relative advantages of the liquid chromatography coupled to a time of flight mass spectrometer (LCMS-TOF) technique for the comparative time-based degradation intermediates and pathways of 4-chlorophenol (4CP) and 4-nitrophenol (4NP). The ozonation of the analytes solution (100 mL of 2 x 10^-3 M) was done in a sintered glass reactor, with an ozone dose of 0.14 mg min^-1 (O₂/O₃ 10 mL/min). The comparative oxidation results revealed that the 4-chloro- and 4-nitrocatechol pathways via hydroxylation were the major degradation route for 4CP and 4NP. Catechol intermediate was present as a primary breakdown product for the two analytes. Hydroquinone was observed as transient degradation intermediate for 4CP, but was absent for 4NP. Rather, a novel ozonation intermediate 2, 4-dinitrophenol was identified which was further oxidized to 3,6-dinitrocatechol. Several dimer products were identified in the oxidation processes, favored by alkaline conditions with more versatility shown by 4CP. The study provided a great insight into the ozone degradation intermediates and pathways, with some intermediates scarce in literature identified.

Synthesis of CoFe2O4/C nano-catalyst with excellent performance by molten salt method and its application in 4-nitrophenol reduction

CoFe₂O₄/C nano-sheets (NSs) have been synthesized by a facile molten salt method using cheap potassium fulvate as carbon source and sodium chloride as template. The morphology, crystallinity and composition of the materials were analyzed by TEM, XRD and XPS. The study on the catalytic performance of 4-nitrophenol (4-NP) shows that CoFe₂O₄/C-600 nano-catalyst has the highest catalytic activity and the corresponding apparent constant is 1.91 min^-1, this result is higher than that reported in most literatures. Catalytic kinetics of 4-NP reduction was studied in this article, and activation energy (E_a) was calculated to be 14.31 kJ mol^-1. The catalyst also shows good cycle performance and stability. This convenient method provides a reference for the synthesis of MFe₂O₄/C and other nano-metal oxides/C nanocomposite catalysts.

Characterization of non-covalent immobilized Candida antartica lipase b over PS-b-P4VP as a model bio-reactive porous interface

The design of interfaces that selectively react with molecules to transform them into compounds of industrial interest is an emerging area of research. An example of such reactions is the hydrolytic conversion of ester-based molecules to lipids and alcohols, which is of interest to the food, and pharmaceutical industries. In this study, a functional bio-interfaced layer was designed to hydrolyze 4-nitrophenyl acetate (pNPA) and Ricinus Communis (castor) oil rich in triglycerides using lipase b from Candida antarctica (CALB, EC 3.1.1.3). The attachment of CALB was performed via non-covalent immobilization over a polymer film of vertically aligned cylinders that resulted from the self-assembly of the di-block copolymer polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP). This polymer-lipase model will serve as the groundwork for the design of further bioactive layers for separation applications requiring similar hydrolytic processes. Results from the fabricated functional bio-interfaced material include cylinders with featured pore size of 19 nm, d spacing of 34 nm, and ca. 40 nm of thickness. The polymer-enzyme layers were physically characterized using AFM, XPS, and FTIR. The immobilized enzyme was able to retain 91% of the initial enzymatic activity when using 4-nitrophenyl acetate (pNPA) and 78% when exposed to triglycerides from castor oil.

Study on dynamic adsorption of p-nitrophenol by multi-walled carbon nanotubes dispersed cyclodextrin

In this paper, the modified multi-walled carbon nanotubes were prepared by β-cyclodextrin denoted as β-CD-MWNTs. The structure and morphology of β-CD-MWNTs was characterized by TEM and the dynamic adsorption of p-nitrophenol on β-CD-MWNTs was studied by the Thomas model. Some affecting factors of dynamic adsorption and the adsorbent regeneration process such as the sewage concentration, the amount of absorbent in column, including the type of reagent, solid-liquid ratio, regeneration time, and regeneration times were investigated and optimized. The results indicated that the p-nitrophenol removal rate could reach 84% under stuffing 2 g β-CD-MWNTs. The curves of p-nitrophenol's dynamic adsorption conformed to the Thomas model. Moreover, the adsorption capacity of regenerated β-CD-MWNTs was similar to the fresh β-CD-MWNT column. The optimal conditions of regenerations of β-CD-MWNTs were shown as follows: the type of reagent is anhydrous ethanol, the solid-liquid ratio is 200:40 (mg/mL) and the regeneration time is 120 min.

Biosynthesized silver nanoparticles using Bacillus amyloliquefaciens; Application for cytotoxicity effect on A549 cell line and photocatalytic degradation of p-nitrophenol

The present study reports the biosynthesis of silver nanoparticles (AgNPs) using Bacillus amyloliquefaciens MSR5. The cellfree supernatant of B. amyloliquefaciens acted as a stabilizing agent for the synthesis of AgNPs. The synthesized AgNPs were characterized using UV-vis spectrophotometer, PXRD, FTIR, SEM-EDX, DLS, and TEM. TEM image showed the spherical shape of the biosynthesized AgNPs and it was found to be 20-40 nm in range. In this study, the AgNPs were prepared by ultrasonic irradiation. The stability of the AgNPs was found to be -33.4 mV using zeta potential. The catalytic 4-nitrophenol (4-NP) degradation by AgNPs was examined under solar irradiation and furthermore, the effects of several degradation parameters were studied. The biosynthesized AgNPs exhibited a strong chemocatalytic action with a comprehensive degradation (98%) of 4-NP to 4-aminophenol (4-AP) using NaBH₄ within 15 min. In addition, MTT assay was performed to evaluate the cytotoxicity of the biosynthesized AgNPs (10 - 200 μg). The results have shown that the AgNPs exhibited significant activity on A549 cells, which was dosedependent. The study elucidates the AgNPs synthesized using cellfree culture supernatant can be used for the elimination of hazardous pollutants from wastewater.

Nanozyme-assisted technique for dual mode detection of organophosphorus pesticide

A novel dual-mode analytical method by employing nanozyme was developed for the detection of organophosphorus pesticides (OPP) for the first time. The detection principle is that the pesticide could be hydrolyzed to para-nitrophenol (p-NP) in the presence of nanoceria as nanozyme. p-NP exhibits the bright yellow color, and its color intensity has a positive correlation with the pesticide concentration. Meanwhile, the characteristic absorption peak at 400 nm of p-NP increases gradually with the raised concentration of pesticide. Therefore, a dual-mode method including smartphone-based colorimetric and spectroscopic strategies was rationally developed. Herein, methyl-paraoxon was selected as the representative compound. Under the optimum conditions, the detection limits of both two strategies were calculated to be 0.42 μmol L^-1. Finally, the present method was successfully applied in three edible medicinal plants (Semen nelumbinis, Semen Armeniacae Amarum, Rhizoma Dioscoreae). The present work offers a reliable and convenient approach for routine detection of pesticide based on two different detection mechanisms.

Yellow-emitting carbon dots for selective detecting 4-NP in aqueous media and living biological imaging

A facile and economical hydrothermal approach is reported for preparing fluorescent nitrogen-doped carbon dots (N-CDs) via using o-phenylenediamine and dicyandiamine. Herein, the bright-yellow-emissive N-CDs are uniformly dispersed spherical nanoparticles with favorable solubility, superior photoluminescence and photobleaching resistance. The fluorescence intensity of N-CDs is linearly quenched by 4-nitrophenol (4-NP) over a concentration range of 0.1-39 μM, corresponding to a detection limit (LOD) of 0.05 μM. Based on this phenomenon, a 4-NP-detection method is exploited and applied to real samples analysis. The synthesized N-CDs are highly biocompatible and capable of biological imaging. Therefore, they are excellent candidates for live biological imaging.

Sunflower stalk-derived biochar enhanced thermal activation of persulfate for high efficient oxidation of p-nitrophenol

Sunflower stalk-derived biochars (BC) were prepared at various temperatures (i.e., 500, 650, and 1000 °C) and demonstrated as a highly efficient catalyst in persulfate (PS) activation for the oxidation of p-nitrophenol (PNP) at 60 °C. The apparent PNP oxidation rate constant in the BC500 (0.1543 L mol^-1 S^-1), BC650 (0.6062 L mol^-1 S^-1), or BC1000 (2.1379 L mol^-1 S^-1) containing PS system was about 2, 8 and 28 times higher than that in PS/PNP (0.0751 L mol^-1 S^-1) system, respectively. The effect of reaction temperature on PNP oxidation was also investigated. Furthermore, the radical quenching tests and electron paramagnetic resonance spectroscopy (EPR) were employed to investigate the sulfate and hydroxyl radicals for PNP oxidation. The Raman results suggested that the defective sites on biochars possess vital role for oxidation of PNP in PS system. The possible activation pathway of PS/BC was proposed that the defective sites on BC were involved for weakening the O-O bond in PS and subsequently cleaving O-O bond by heat to generate sulfate radical. The oxidation of PNP at low concentration (below 100 μg L^-1) was completely removed in urban wastewater by PS/BC system within 30 min. This work would provide new insights into PS activation by BC catalyst and afford a promising method for organic pollutant removal in high-temperature wastewater.

Enhanced reactivity and mechanisms of copper nanoparticles modified green rust for p-nitrophenol reduction

This paper describes the reduction of p-nitrophenol by green rusts (GRs) interlayered with common inorganic anions (Cl^-, SO₄^2- and CO₃^2-). Modifying of GRs with zero-valent Cu nanoparticles (Cu⁰ NPs) can greatly enhance the reductive reactivity of GRs via the formation of a galvanic couple between the GRs and the Cu⁰ NPs, as confirmed by an increased corrosion current. The direct addition of Cu⁰ NPs excludes the possible formation of less active mono-valent Cu in the GRs/Cu²⁺ system. Oxidation of GRs does not occur upon the addition of Cu⁰ NPs, thus a decline in electron transfer from the oxidized GRs to the Cu⁰ NPs is avoided. The optimum Cu⁰ NPs loading on GR_Cl is 0.5% wt. The GR_Cl/Cu⁰ NPs retains high reactivity in the studied pH range from 7 to 10, while the presence of NO₃^-, PO₄^3-, SO₄^2-, CO₃^2- and humic acid inhibits PNP reduction by the GR_Cl and GR_Cl/Cu⁰ NPs. The GR_Cl/Cu⁰ NPs system is less susceptible to the presence of CO₃^2- and humic acid compared to the pure GR_Cl system due to the migration of the PNP reduction sites from the GRs to the Cu⁰ NPs. This work sheds light on a new strategy for enhancing GR-based materials for use in groundwater remediation.

Novel visible light enhanced Pyrite-Fenton system toward ultrarapid oxidation of p-nitrophenol: Catalytic activity, characterization and mechanism

The activities of heterogeneous Fenton and Photo-Fenton processes using pyrite (FeS₂) prepared via a solvethermal method were evaluated by oxidation of p-nitrophenol (PNP). PNP could be completely ultrarapidly oxidized by Pyrite-Photo-Fenton (Pyrite-PF) system within 4 min, versus 10 min in Pyrite-Fenton (Pyrite-F) system. The excellent oxidation performance obtained by Pyrite-PF might be due to accelerated circulation between ferrous ions and ferric ions under visible light illumination, which improved generation of reactive oxygen species (ROS). X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) were applied to ascertain the morphology and crystal structure of fresh-pyrite as well as used-pyrite. According to these results, the synthesized pyrite particles performed eminent stability, and used-pyrite could even generated more ROS including hydroxyl radicals (OH) and superoxide radicals (O₂^-). EPR testing and quenching experiments also confirmed the generations of OH, O₂^- and holes (h⁺) during oxidation processes of PNP in both Pyrite-F and Pyrite-PF systems. The reaction pathway was proposed based on the detected intermediate products including 4-nitrocatechol, 4-nitropyrogallol, hydroquinone, benzoquinone, 1,2,4-trihydroxybenzene and 2,4-dinitrophenol. The mechanisms of PNP degradation in Pyrite-F and Pyrite-PF systems have also been studied by DFT calculations. Pyrite (111) should be responsible for the generations of free OH and surface OH.

Preparation of nitrogen-doped Cu-biochar and its application into catalytic reduction of p-nitrophenol

Nitrogen-doped copper-biochar (N-Cu-biochar) was synthesized via pyrolysis of glucose in the presence of copper and melamine and used as a catalyst in the reduction of p-nitrophenol by NaBH₄. N-Cu-biochar was characterized by field emission scanning electron microscopy/energy-dispersive spectroscopy, Raman spectroscopy, X-ray Diffraction, and Brunauer-Emmett-Teller surface analyzer. The catalytic performance of N-Cu-biochar was evaluated under varying conditions of NaBH₄ concentration, biochar dosage, and initial p-nitrophenol concentration. N-Cu-biochar was composed of ~83% C, ~9% O, and ~8% Cu, with Cu/Cu₂O phases evenly dispersed on graphitic carbon aggregates possessing both macro- and meso-pores. N-Cu-biochar showed superior catalytic ability in mediating p-nitrophenol reduction as compared to Cu-biochar and N-doped biochar, achieving complete reduction of 0.35 mM p-nitrophenol within 30 min at a dose of 0.25 g L^-1. Reduction of p-nitrophenol catalyzed by N-Cu-biochar followed pseudo-first-order kinetics, and the reaction rate was dependent upon NaBH₄ concentration. The overall results indicate that biochar can be a suitable candidate as a support for catalyst synthesis, and N-doped Cu-biochar can be a promising catalyst for the reduction of p-nitrophenol.

Preparation of porous semi-IPN temperature-sensitive hydrogel-supported nZVI and its application in the reduction of nitrophenol

Nanoscale zero-valent iron (nZVI) particles supported on a porous, semi-interpenetrating (semi-IPN), temperature-sensitive composite hydrogel (PNIPAm-PHEMA). nZVI@PNIPAm-PHEMA, was successfully synthesized and characterized by FT-IR, SEM, EDS, XRD and the weighing method. The loading of nZVI was 0.1548 ± 0.0015 g/g and the particle size was 30-100 nm. NZVI was uniformly dispersed on the pore walls inside the PNIPAm-PHEMA. Because of the well-dispersed nZVI, the highly porous structure, and the synergistic effect of PNIPAm-PHEMA, nZVI@PNIPAm-PHEMA showed excellent reductive activity and wide pH applicability. 95% of 4-NP in 100 mL of 400 mg/L 4-NP solution with initial pH 3.0-9.0 could be completely reduced into 4-AP by about 0.0548 g of fresh supported nZVI at 18-25 °C under stirring (110 r/min) within 45 min reaction time. A greater than 99% 4-NP degradation ratio was obtained when the initial pH was 5.0-9.0. The reduction of 4-NP by nZVI@PNIPAm-PHEMA was in agreement with the pseudo-first-order kinetics model with K_obs values of 0.0885-0.101 min^-1. NZVI@PNIPAm-PHEMA was able to be recycled, and about 85% degradation ratio of 4-NP was obtained after its sixth reuse cycle. According to the temperature sensitivity of PNIPAm-PHEMA, nZVI@PNIPAm-PHEMA exhibited very good storage stability, and about 88.9% degradation ratio of 4-NP was obtained after its storage for 30 days. The hybrid reducer was highly efficient for the reduction of 2-NP, 3-NP, 2-chloro-4-nitrophenol and 2-chloro-4-nitrophenol. Our results suggest that PNIPAm-PHEMA could be a good potential carrier, with nZVI@PNIPAm-PHEMA having potential value in the application of reductive degradation of nitrophenol pollutants.

Construction of rGO wrapping Cu2O/ZnO heterostructure photocatalyst for PNP and PAM degradation

Copper and zinc composite oxides (Cu₂O/ZnO) were synthesized by an impregnation-reduction-air oxidation method. A series of Cu₂O/ZnO/rGO ternary composites were prepared by coupling with graphene oxide (GO) with different mass fractions in a solvothermal reaction system. The microscopic morphology, crystal structure, and optical characteristics of the photocatalysts were characterized. The degradation of p-Nitrophenol (PNP) and polyacrylamide (PAM) by photocatalytic materials under simulated solar irradiation were studied, and the degradation kinetics were also investigated. The results showed that cubic Cu₂O was modified by ZnO nanorods and distributed on rGO nanosheets. The ternary Cu₂O/ZnO/rGO nanocomposites have stronger simulated solar absorption ability and higher photodegradation efficiency than pure ZnO and binary Cu₂O/ZnO nanocomposites. When the amount of Cu₂O/ZnO/rGO-10 was 0.3 g L^-1, the degradation rate of 10 mg L^-1 PNP reached 98% at 90 min and 99.6% of 100 mg L^-1 PAM at 30 min. The photocatalytic degradation processes of PNP and PAM all followed the pseudo-first-order kinetic model. Free radical trapping experiments showed that superoxide radicals were the main active substances to improve photocatalytic efficiency. In addition, after four recycles, the catalytic efficiency of Cu₂O/ZnO/rGO-10 was still over 90%. It showed that Cu₂O/ZnO/rGO-10 was a promising catalyst for wastewater treatment because of its good photostability and reusability.

Ozonation process intensification of p-nitrophenol by in situ separation of hydroxyl radical scavengers and microbubbles

The ozonation efficiency for removal of recalcitrant organic pollutants in alkaline wastewater is always low because of the presence of some hydroxyl radical scavengers. To solve this problem, the O₃/Ca(OH)₂ system was put forward, and p-nitrophenol (PNP) was chosen to explore the mechanism of this system. The effects of key operational parameters were studied respectively; the Ca(OH)₂ dosage 3 g/L, ozone inlet flow rate 3.5 L/min, ozone concentration 65 mg/L, reactor pressure 0.25 MPa, and temperature 25 °C were obtained as the optimal operating conditions. After 60 min treatment, the organic matter mineralized completely, which was higher than the sum of the ozonation-alone process (55.63%) and the Ca(OH)₂ process (3.53%). It suggests that the calcium hydroxide in the O₃/Ca(OH)₂ process possessed a paramount role in the removal of PNP. The liquid samples and the precipitated substances were analyzed by gas chromatography mass spectrometry, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy; it was demonstrated that Ca(OH)₂ could accelerate the generation of hydroxyl radical and simultaneously in situ separate partial intermediate products and CO₃ ^2- ions through some precipitation reactions.