Green Chemistry Route Research Articles

Interface coupling of octahedron Cu2O with reduced graphene oxide for enhanced photocatalytic and photoelectrochemical activity

Graphene oxide (GO) has been recognized as an ideal substrate material of semiconductor photocatalysts to achieve superior properties. Herein, Cu2O/reduced graphene oxide hetero-structures (Cu2O/rGO), featured by octahedron Cu2O with highly exposed {111} facets in-situ anchored on the framework of rGO nanosheets, were constructed via a green wet chemistry route at room temperature. During the reactions, Cu2+ ions that were adsorbed on GO could act as the nucleation sites of Cu2O while GO was further converted into rGO under the reduction of glucose, forming a robust hetero-interface of C–O–Cu bonding. Owning to the improved photon capture ability and carrier separation efficiency, the optimized Cu2O/rGO exhibits about 3.5 and 9.3 times enhancement of photocurrent intensity and photocatalytic activity, respectively, as compared to those of pure Cu2O. Meanwhile, the correlation among rGO content, structure and photocatalytic activity of Cu2O/rGO was demonstrated. This work presents a rational route and deep insight for the interface coupling within metal oxide/carbon material hetero-structures for advanced catalytic applications.

Influence of electrodeposited Cu2ZnSnS4 films for the reduction of 4-nitrophenol through electronic relay approach and serve as photoelectrode in PEC device

We explore the possibility of thin film Cu2ZnSnS4 (CZTS) as an effective catalyst for the reduction of 4-nitrophenol to 4-aminophenol in presence of NaBH4 through electronic relay process with the rate constant of 0.20 min−1, also as photoelectrode material for low-cost photoelectrochemical solar cells. Cu2ZnSnS4 thin films with thickness of ∼ 2 μm have been synthesized by an electrochemical approach. The electrochemical bath contained an aqueous solution of Cu(NO3)2·3H2O, Zn(NO3)2.6H₂O, SnC2O4 and Na2S2O3 with Citric acid as a chelating ligand at an optimum pH∼3.65. The morphology, composition, and optical properties were characterized by XRD, FE-SEM, HR-TEM, UV–Vis, FT-IR, and EPR analysis. The growth kinetics of CZTS have been invested with different time intervals, also changes of band gaps of deposited material have been noticed. Cyclic voltammetry of the electrode is done to predict the co-deposited system in the quaternary semiconductor in 0.1 M KCl as supporting electrolyte. The deposited Kesterite phase of CZTS has been systematically investigated to serve as an effective counter electrode material for photoelectrochemical (PEC) energy conversion in 0.5 M polysulfide (Na2Sx) redox couple which showed an efficiency of ∼ 4.395 %. The development of a facile and green chemical route for the preparation of a well crystallized and stable CZTS photoelectrode still remains a challenge.

Advancing photocatalytic activity through a green route: Bismuth ferrite@molybdenum trioxide heterostructure for sustainable water treatment

Photocatalysis has become increasingly pervasive in the chemical industry, profoundly impacting operational costs. However, an ideal photocatalyst must possess characteristics such as excellent reactivity, high selectivity, prolonged stability, low toxicity, and cost-effectiveness. Moreover, it should facilitate the efficient separation of photo-generated charge carriers, thereby minimizing recombination rates. In pursuit of advancing photocatalytic activity for sustainable water treatment, this investigation focused on synthesizing a groundbreaking photocatalyst, the Bismuth Ferrite@Molybdenum trioxide heterostructure, using an eco-friendly green chemistry technique with pomegranate extract. This approach aligns with the goal of environmental sustainability and represents a novel contribution to the field. Employing a comprehensive approach, advanced characterization techniques such as XRD, SEM, FT-IR, and UV–Vis were applied to analyze the material's structural, morphological, and optical properties. According to the characterization results, the heterostructure demonstrates superior photocatalytic efficiency, heightened crystallinity, and reduced recombination rates during dye degradation for water treatment compared to both individual photocatalysts. Notably, the composite catalyst exhibits a synergistic impact, outperforming individual BiFeO3 and MoO3 photocatalysts. SEM observations confirm the successful integration of rod-like MoO3 and cylindrical BiFeO3 morphologies, highlighting the strategic combination achieved through the green chemistry route. Furthermore, UV–Vis spectroscopy reveals key optical parameters, emphasizing a narrow bandgap energy of 2.74 eV with a high refractive index of 2.43 eV. The exceptional efficacy of the heterostructure in degrading dyes within the visible spectrum, surpassing expectations within a 4-hour timeframe, highlights its efficiency and precision. Remarkably, achieved degradation rates for Rhodamine B dye (98 %), Methyl Blue (96 %), and Methyl Orange dye (95 %) highlights the promising role of proposed photocatalytic system in effectively addressing water pollutant challenges.

Cadmium nanocluster as a safe nanocarrier: biodistribution in BALB/c mice and application to carry crocin to breast cancer cell lines.

Metal nanoclusters are emerging nanomaterials applicable for drug delivery. Here, the toxicity and oxidative stress induction of divalent cationic cadmium (Cd2+) was compared with a Cd in the form of nanocluster. Then, it was used for targeted drug delivery into breast cancer cell lines. Using a green chemistry route, a Cd nanocluster (Cd-NC) was synthesized based on bovine serum albumin. After characterization, its genotoxicity and oxidative stress induction were studied in both in vitro and in vivo. After that, it was conjugated with hyaluronic acid (HA). The efficiency of hyaloronized-Cd-CN (HA-Cd-NC) for loading and releasing crocin (Cro), an anticancer phytochemical, was studied. Finally, it was applied for cell death induction in a panel of breast cancer cell lines. The comet assay results indicated that, unlike Cd2+ and potassium permanganate (KMnO4), no genotoxicity and oxidative stress was induced by Cd-NC in vitro. Then, the pharmacokinetics of this Cd-NC was studied in vivo. The data showed that Cd-NC has accumulated in the liver and excreted from the feces of mice. Unlike Cd2+, no toxicity and oxidative stress were induced by this Cd-NC in animal tissues. Then, the Cd-NC was targeted toward breast cancer cells by adding HA, a ligand for the CD44 cell surface receptor. After that, Cro was loaded on HA-Cd-NC and it was used for the treatment of a panel of human breast cancer cell lines with varying degrees of CD44. The half-maximal drug inhibitory concentration (IC50) of Cro was significantly decreased when it was loaded on HA-Cd-NC, especially in MDA-MB-468 with a higher degree of CD44 at the surface. These results indicate the higher toxicity of Cro toward breast cancers when carried out by HA-Cd-NC. The Cd-NC was completely safe and is a promising candidate for delivering anticancer drugs/phytochemicals into the targeted breast tumors.

Engineering 2D Photocatalysts for Solar Hydrogen Peroxide Production

AbstractSolar energy can be utilized in photocatalysis technology to realize light‐driven hydrogen peroxide (H2O2) production, a green chemical synthesis route. Designing high‐performance photocatalysts is critical to achieving practical solar H2O2 production. During the past decade, significant research progress is made in photocatalytic materials for H2O2 production. Particularly 2D materials‐based photocatalysts stand out due to their unique physical and chemical properties. This review highlights the intricate relationship between 2D material innovation and photochemical H2O2 production. It starts with the fundamental principles of photochemical H2O2 generation, focusing on crucial steps such as photon absorption, carrier dynamics, surface reactions, and the challenges that 2D materials can solve at each step. Then, various 2D materials‐based photocatalysts for solar H2O2 production are introduced in detail. Engineering strategies to optimize the photocatalytic performance are discussed afterward. Finally, the challenges and future opportunities for designing 2D materials‐based photocatalysts for solar H2O2 production are outlined. This review is expected to inspire the engineering of 2D materials‐based photocatalysts for the green synthesis of H2O2 and the conversion of solar energy to other chemicals.

Product Yield Increasing More Than 20 Times Achieved by Reducing Water Poisoning for Direct Diethyl Carbonate Synthesis.

Diethyl carbonate (DEC) synthesis from CO2 and ethanol is a typical green chemical route for sustainable development and cleaner production. However, the bottleneck problem of a low DEC yield is still not solved at present. The DEC yield still maintains 0.5-5.0% unless expensive third additives are added. Compared to the cheap price of DEC, the third additives are generally more expensive. It is not advisible to use expensive chemicals to prepare cheap chemicals. In this work, the (ZrO2)1.0/(Fe2O3)1.0 catalyst was prepared by a novel template-precipitation method and the DEC yield of the DEC direct synthetic reaction only from CO2 and ethanol without third additives obtained 1.95%. After a series of supported catalysts were prepared, the DEC yield reached up to 46.1% for the (ZrO2)1.0/(Fe2O3)1.0@3A-CaO-CaC2 catalyst. This carrier can also be applied to other catalyst systems. CO2-TPD, NH3-TPD, and XRD were measured to analyze the microstructure and catalytic mechanism. Active center site theory was proposed to explain the intrinsic mechanism of catalyst activity. This new discovery of the mechanism and the DEC yield removed obstacles for the application of this reaction.

Green chemistry route to chitosan hydrogels and investigation of the materials as efficient dye adsorbents

Abstract Biopolymer-based materials for the adsorption of toxic dyes represent an interesting class of materials for environmental applications. Here we report on chitosan as the starting material for synthesizing dye adsorbents. In particular, the synthesis, characterization, and cationic dye adsorption properties of chitosan hydrogel adsorbents are reported. Polyanionic itaconated chitosan derivatives were synthesized in solvent-less conditions for the first time. Itaconated chitosan was cross-linked using thiol-ene chemistry to obtain hydrogels. The influence of the incorporated carboxylate groups and the cross-linker fraction on the adsorption of Methylene Blue (MB) was investigated. In addition, the impact of pH, adsorbent dose, initial concentration, and ionic strength were investigated to determine the optimum conditions for MB uptake, and the dye uptake kinetics, adsorption isotherms, selectivity, and reusability of the adsorbents were unveiled. A maximum adsorption capacity of 556 mg/g could be achieved, outperforming commercial activated charcoal and ion exchange resins. Furthermore the chitosan hydrogel adsorbents were shown to capture >90 % of cationic MB from a binary equimolar mixture with the anionic dye Methyl Orange. Since the adsorbents can be regenerated and re-used afterwards at least 20 times, retaining a high dye adsorption fraction of >95 %, these materials are promising candidates for environmental applications.

Redox-active green-electrode: Plant-extract based rutin and caffeic acid functionalized MWCNT for scanning electrochemical microscopy imaging and selective electrocatalytic oxidative sensing of dopamine

A straightforward, environmentally friendly, and rapid in-situ electrochemical functionalization of Rutin (Rut) and Caffeic acid (Caf) on a multiwalled carbon nanotube-modified glassy carbon electrode, denoted as GCE/MWCNT@Herb-Redox (Herb-Redox =redox active species from the plant extract), has been demonstrated. This method utilizes an eco-friendly, plant-based water extract from Indian Borage (Coleus amboinicus), referred to as IBE, as a precursor sample. The as-prepared molecular bio-electrode showed a well-defined and stable surface-confined redox response at standard electrode potentials, Eo’ = 0.160 and 0.200 V vs Ag/AgCl in pH 7 phosphate buffer solution. By performing physicochemical and molecular characterisations using TEM, SEM, UV–Vis, FTIR, high-performance thin-layer chromatographic techniques, it has been confirmed that Rut and Caf from the Herbal-plant were selectively immobilized on the MWCNT-modified electrode. Using scanning electrochemical microscopy (SECM), the electroactive sites of the molecular-electrode were mapped. The electrocatalytic function of the GCE/MWCNT@Herb-Redox was demonstrated by performing a dopamine (DA) oxidation reaction as a model system in pH 7 PBS using CV and amp-it techniques. The results showed 100—10,000 times increase in the DA- oxidation current response over the values quoted with many of the literature reports highlighting the efficient functionality of the new molecular electrocatalytic system. As a proof of concept, batch injection analysis based elegant dopamine sensing using screen-printed electrode/MWCNT@Herb-Redox as an electrochemical detector has been demonstrated and there is no biochemical interference was observed. Since the electrochemical approach follows a green chemistry route for the modification, this bioelectrode showed a new platform for eco-friendly electrocatalytic applications.

Nanocatalytic and antimicrobial potency of CQD@Pd nanoparticles: Experimental and theoretical approach

A single-pot approach has been developed for the fabrication of novel heterogeneous nanocatalyst of carbon quantum dots doped palladium (CQD@Pd-NPs) nanoparticles. Herein, Aegle marmelos fruit extract was utilized as a reducing and capping agent for the fabrication of CQD@Pd-NPs. Synthesis of metallic nanoparticles through green chemistry route is environment beneficial technology owing to its low cost and ecological compatibility. The formation of CQD-NPs and CQD@Pd-NPs was confirmed with high-end sophisticated techniques and theoretical studies. The computational analysis revealed a discernible decrease in the band gap value (Egap = ELUMO - EHOMO) from 0.08 eV to 0.03 eV upon the introduction of Pd atoms into carbon quantum dots (CQDs). Therefore, computational data also authenticates the stability of the CQD@Pd-NPs nanocatalyst which was predominantly supported by electrostatic interaction between Pd and CQDs. The developed nanocatalyst has vouched for an effective candidature in the Suzuki-Miyaura and Mizoroki-Heck coupling reactions with a superior selectivity for product formation. The excellent antibacterial properties against E. coli and S. aureus were further supported by visualizing bacterial growth, inhibition zone, FESEM results and molecular docking studies. Moreover, the nanocatalyst displayed facile separation from the reaction system and showcased efficient recyclability with minimal activity loss. This further supports an effective potential over existing commercial catalysts and holds immense future prospective in industrial applications.

Green synthesis of BiVO4/Eco-graphene nanostructures for the elimination of sulfamethoxazole by adsorption and photo-degradation using blue LED light

Photo-catalysts based on BiVO4 (BV) and Eco-graphene (EG) were synthesized and obtained in a single step with high-quality properties. These nanostructures (NEs) were obtained through a green chemistry route and by adding 2, 3, and 5 wt% of a homemade EG. The BV/X EG NEs (where X = corresponds to the weight % of EG) demonstrated high photocatalytic activity, obtaining Sulfamethoxazole degradation percentages of 40, 45, 52, and 57 for BV, BV/2 EG, BV/3 EG, and BV/5 EG respectively, using a blue LED light. In addition, it was observed that the presence of EG slightly affected the surface area and porosity of BV. Moreover, it was observed that the presence of EG stabilized the scheelite monoclinic phase (m-s), and decreased the crystal size and band-gap values of BV-based samples. It was detected that EG contents increased the BV reduction, creating oxygen vacancies and V4+ states, which favored electron transfer, enhanced the photo-catalytic activity, and decreased the recombination rate. The adsorption influence of the BV/EG system was also studied. Finally, the stability tests of these materials after four cycles of reuse allowed keeping practically the full degradation capacity, demonstrating that these NEs represent a promising material driven by visible light that can be used for wastewater decontamination in the presence of drugs.

Integrating climate policies in the sustainability analysis of green chemicals.

New and enhanced processes will not be the only drivers toward a sustainable chemical industry. Implementing climate policies will impact all components of the chemical supply chain over the following decades, making improvements in energy generation, material extraction, or transportation contribute to reducing the overall impacts of chemical technologies. Including this synergistic effect when comparing technologies offers a clearer vision of their future potential and may allow researchers to support their sustainability propositions more strongly. Ammonia and methanol production account for more than fifty percent of the CO2 emissions in this industry and are, therefore, excellent case studies. This work performs a prospective life cycle assessment until 2050 for fossil, blue, wind, and solar-based technologies under climate policies aiming to limit the global temperature rise to 1.5 °C, 2 °C, or 3.5 °C. The first finding is the inability of fossil-based routes to reduce their CO2 emissions beyond 10% by 2050 without tailored decarbonisation strategies, regardless of the chemical and climate policy considered. In contrast, green routes may produce chemicals with around 90% fewer emissions than today and even with net negative emissions (on a cradle-to-gate basis), as in the case of methanol (up to -1.4 kg CO2-eq per kg), mainly due to the contributions of technology development and increasing penetration of renewable energies. Overall, the combined production of these chemicals could be net-zero by 2050 despite their predicted two to fivefold increase in demand. Lastly, we propose a roadmap for progressive implementation by 2050 of green routes in 26 regions worldwide, applying the criterion of at least 80% reduction in climate change impacts when compared to their fossil alternatives. Furthermore, an exploratory prospective techno-economic assessment showed that by 2050, green routes could become more economically attractive. This work offers quantitative arguments to reinforce research, development, and policymaking efforts on green chemical routes reliant on renewable energies.

Efficient capture of benzene and its homologues volatile organic compounds with protic [MIM][NTF2] and aprotic [EMIM][NTF2] ionic liquids: Experimental and computational thermodynamics

Using new green solvents to effectively capture volatile organic compounds (VOCs) is considered as an attractive green sustainable chemical development route. In this work, benzene, toluene, ethylbenzene and p-xylene (BTEX) were selected as typical aromatic VOCs. The gas absorption performance of proton [MIM][NTF2] and aprotic [EMIM][NTF2] ionic liquids (ILs) for BTEX were studied by computational thermodynamics combined with gas absorption experiments. Absorption experiments of BTEX and regeneration experiments of ILs were carried out at different temperatures, and ILs had good stability. The interaction type and intensity were determined by Interaction Region Indicator (IRI) analysis of IL-BTEX blend systems. The C-H···π and π-π interaction between imidazole ring and BTEX were the direct reason why ILs can efficiently absorb BTEX. Molecular dynamics simulations were performed to explore the diffusion behavior of gas in ILs. The increase of methyl group increases the interaction strength of the system, and the fractional free volume of IL-BTEX blend systems decreases gradually, which limits the diffusion of BTEX. Non-bond interaction analysis shows that van der Waals interaction was the main driving force of BTEX absorption in ILs.

A Mechanistic Study on the Hydrolysis of Cyclic Ketene Acetal (CKA) and Proof of Concept of Polymerization in Water

AbstractThe present work systematically investigates the hydrolysis mechanism of cyclic ketene acetal (CKA) monomers in detail and explores polymerization in water under organic solvent‐free and surfactant‐free conditions. To understand the effect of CKA structure on hydrolysis, the ring size of the monomers is varied from 5–8‐membered rings systematically and hydrolysis experiments are performed. In all cases, hydrolysis yields monoacetylated diol products. Deuterium and 17O‐isotopic labeled experiments are carried out for 5‐ and 7‐membered‐(2‐methylene‐1,3‐dioxepane, MDO) CKAs to understand the reaction pathway. The experimental analysis from the reaction of CKA with water revealed that the increasing hydrophobicity from 5–8‐membered rings and the pH of the reaction medium play important roles in the order of reactivity. Density functional theory (DFT) and experimental studies demonstrated that basic reaction conditions have some control over the hydrolysis rate of CKA. Despite this progress, achieving controlled polymerization of CKA in water while suppressing hydrolysis remains challenge. Only up to 3 mol% CKA incorporation is attained in polyacrylate and polyacrylamide backbone via radical ring‐opening polymerization (rROP) of MDO and 8‐membered CKAs with 2‐hydroxyethyl acrylate (HEA) and acrylamide (AAm) in water. The results serve a proof of concept for advancing aqueous copolymerizations using CKA monomers.

Surface-Enhanced Raman Spectroscopy of Benzylpenicillin Using Silver Nanocrystals Modified with Moroccan Plant Extracts

Green chemical routes for the synthesis of colloidal metal nanocrystals have been of great interest, namely in the context of nanosciences associated with biological applications. Among these methods, the synthesis of metal colloids using medicinal plant extracts originates nanocrystals having surfaces modified with chemical compounds of biological origin, which can be further explored in association with conventional pharmaceutics. In this context, the development of spectroscopic methods that seeks for understanding the potential benefits of using formulations that contain natural compounds and metal nanoparticles with therapeutic properties is of relevance. This research describes the chemical synthesis of silver colloids via the reduction of Ag(I) in the presence of distinct aqueous plant extracts. The selected extracts were obtained from Moroccan plants that have been used in traditional therapeutic practices over the centuries. The method led to stable colloids comprising polydispersed Ag nanocrystals that show surface-enhanced Raman scattering (SERS) activity. As an illustrative scenario, these colloids have been applied to the SERS detection of the natural β-lactam antibiotic benzylpenicillin, also known as penicillin G (PG). Our results indicate that all the Ag colloids tested with the different plant extracts are SERS-active for PG without showing detrimental interference from chemical adsorbates originated from the extracts. Therefore, this spectroscopic method can be further explored for monitoring nanoformulations of pharmaceuticals and metal colloids obtained using biological synthesis.

An Eco‐Friendly and Switchable Carbon‐Based Catalyst for Protection‐Deprotection of Vicinal Diols

AbstractEven though protection‐free protocols represent a key principle of green chemistry, both protection and deprotection routes are indispensable strategies in synthetic pursuits, especially towards highly functionalized pharmaceuticals and agrochemicals, often decorated by promiscuous OH or NH groups, among others. Herein a sustainable carbon‐based catalyst is reported that efficiently promotes the protection of 1,2‐diols as isopropylidene ketals under heterogeneous conditions, affording products in high conversion and yields. Grafting of sulfonate groups onto the high‐surface‐area carbon creates a solid acid catalyst with high performance for acetalization under mild thermal conditions. Interestingly, the same catalyst can be employed for the inverse deprotection step leading to the parent diols with comparable efficiency. Along with a detailed catalyst's characterization, critical issues related to catalyst loading, reaction scope, and selectivity were thoroughly optimized. The catalyst can be recycled, and no impurities caused by leaching could be observed.

Metal-free synthesis of quinazolinone from 2-amino benzonitrile in the presence of formic acid as a C1 source

Quinazolinones are primarily found in natural products and serve as the basic building blocks in a plethora of commercially available drugs. Quinazolinones are nitrogen-containing heterocyclic compounds having a range of biological activities. The traditional synthesis of quinazolinone often employs toxic and environmentally harmful chemicals, making it imperative to find alternative green chemistry routes. In this study, we report the synthesis of quinazolinones from 2-aminobenzonitrile employing formic acid as a C1 source in the presence of triethylamine as a base. This study’s main objective is to develop a catalyst-free synthesis method, utilizing the green chemistry principles of atom economy and reducing toxicity. The reaction was conducted under mild conditions and provided high yields of the target compounds. The findings demonstrate that this simple and efficient synthetic approach is a promising alternative to conventional routes and provides a sustainable solution for synthesising quinazolinone derivatives. The current strategy enabled broad substrate scope for synthesizing quinazolinones with good to excellent yields.

Construction, characterization and application of locust bean gum/Phyllanthus reticulatus anthocyanin - based plasmonic silver nanocomposite for sensitive detection of ferrous ions

Iron is a transition metal of tremendous eco-physiological significance. This work aimed at constructing a simple plasmonic Ag-nanocomposite (LBG/PRAg-NC) based on locust bean gum and Phyllanthus reticulatus anthocyanin in a sustainable manner for the optical detection of ferrous ions (Fe2+) in aqueous solution. LBG/PRAg-NC was prepared via a green chemistry route and thoroughly characterized for its physico-chemical and plasmonic attributes. Successful synthesis of LBG/PRAg-NC under room temperature with Phyllanthus reticulatus anthocyanin as reductant and locust bean gum as stabilizer was accomplished within 15 min. LBG/PRAg-NC exhibited small size (∼8.04 nm), spherically shaped nanosilver, with good colloidal dispersion, stability and prominent SPR absorption peak at 420 nm. XPS analysis revealed the existence of both Ag0 and Ag + species embedded in the biopolymer support. Furthermore, LBG/PRAg-NC was highly selective for Fe2+ as opposed to other interferents including Fe3+. The presence of Fe2+ engendered a redox oxidation of the analyte by the Ag+ species, prompting a rapid, concentration dependent increase in color and SPR absorption band intensity of LBG/PRAg-NC colloidal solution. In aqueous solution, the probe displayed a good linear range for Fe2+ (0.1–100 μM), and a low detection limit (LOD of 0.38 μM). The obtained detection limit is much lower than the guideline limit of Fe2+ content in drinking water, ∼5 μM. Additionally, the probe was successfully applied in determination of Fe2+ in aqueous solutions of apple juice, iron supplement tablet, and tap water, with commendable analytical performances. Therefore, our research findings demonstrate a facile, efficacious, cost-effective, and eco-friendly approach for the sustainable synthesis of plasmonic Ag-nanocomposites based solely on locust bean gum and Phyllanthus reticulatus anthocyanin. Importantly, these results validate the capacity of plasmonic Ag-nanocomposite constructed via green chemistry route as a simple, rapid, and selective probe for effective monitoring of trace amounts of Fe2+ in aqueous environment.

Green synthesis of zinc oxide nanoparticles using lychee peel and its application in anti-bacterial properties and CR dye removal from wastewater

In nanoscience and nanobiotechnology, using plant extracts in synthesizing metal nanoparticles (NPs) has recently come to light as an exciting opportunity with several benefits over traditional physicochemical methods. In the present work, zinc oxide (ZnO) based nanoparticles (NPs) were synthesized by green chemistry route using lychee peel extract to capture hazardous congo red dye from wastewater and illustrate their antimicrobial behavior. The X-Ray Diffraction (XRD) spectra confirm the wurtzite crystal structure, and Fourier Transform Infrared (FTIR) spectra confirm the functional group in ZnO, which is suitable for dye adsorption. It was found that the NPs were spherical and had a size of <10 nm. The synthesized ZnO NPs could effectively remove >98% of CR dye from wastewater within 120 min of contact time at a wide pH range from 2 to 10. The primary mechanism involved in removing dye was the electrostatic interaction between ZnO adsorbent and CR dye. The antimicrobial performance of synthesized ZnO NPs was found to show 34% inhibition against Bacillus subtilis (ATCC 6538), 52% against Escherichia coli (ATCC 11103), 58% against Pseudomonas aeruginosa (ATCC 25668) and 32% against Staphylococcus aureus (ATCC 25923) using well diffusion assay. ZnO demonstrates a suitable anti-bacterial property over both gram-positive and gram-negative pathogenic bacteria. Overall, the green synthesized method for developing ZnO NPs shows promising and significant anti-bacterial performance and is a highly potential adsorbent for removing CR dye from wastewater.

A “turn-on” fluorescent sensor for Pb2+ detection based on nitrogen doping carbon dots

Nitrogen-doped carbon dots (N-CDs) were synthesized via a green chemistry route and subsequently employed as a fluorescent sensing probe for Pb2+ ions. Through a series of characterizations, the properties of the obtained N-CDs were comprehensively deciphered and investigated. In particular, the specific fluorescence response for Pb2+ was obviously promoted by a “turn-on” mode, even in the presence of other interfering metal ions. According to the established N-CDs sensors, a linear correlation of fluorescence intensity and Pb2+ concentration was formed in the range of 0∼50 μM. This sensing platform displayed a sensitive and selective detection towards Pb2+ ions, in which a limit of detection (LOD) was achieved up to 0.92 μM. Finally, the underlying sensing mechanism towards Pb2+ was proposed by a photo-induced electron transfer (PET) inhibition process, which was demonstrated by a density functional theory (DFT) simulation study. This work provides a promising platform for the analysis of Pb2+ ions in aqueous environmental samples.

Selective synthesis of dimethyl carbonate via the coupling reaction of CO2 and alcohols by the synergistic catalysis of silver sulfadiazine and superbase

The three-component coupling of methanol, CO2 and propargyl alcohol to manufacture dimethyl carbonate (DMC) provides a new, thermodynamic favorable and green chemical synthesis route. In this work, to overcome the problems of low DMC yield and slow conversion rate of intermediates, the synergistic catalytic strategy of silver sulfadiazine and superbase is developed to improve the reaction efficiency. The effect of various parameters i.e. catalyst and cocatalyst types, catalyst loading, solvent, temperature, proportion of raw materials, pressure and time on the coupling reactions is investigated in detail. Under the optimal conditions, the selectivity of DMC is 89.5% with the yield of 55.6%. And the effect of alkyne derivative α-monosubstituted propargyl alcohol on the efficiency and selectivity of DMC are studied also. The mechanism study shows that propargyl alcohols with different structures apparently affect the reaction process, and the synergistic catalysis of silver sulfadiazine/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is the reason for the high yield and selectivity of DMC.