Values Of Apparent Rate Constants Research Articles

Synergistic reduction of nitrophenols by Au-CDs nanoconjugates with NaBH4

Developing sustainable and innovative approaches for the efficient reduction of nitrophenols is crucial for environmental remediation, for managing health concerns posed by their widespread presence as hazardous pollutants in industrial effluents and contaminated water. We report the use of 12.9 ± 1 nm (TEM data) sized gold carbon dot nanoconjugates (Au@CDs) for catalytic conversion of o, m, p-nitrophenols to aminophenols by sodium borohydride. A simple approach was followed to synthesize ultra-small and highly stable Au@CDs, using citric acid and PEG as reducing and stabilizing agents. X-ray diffraction analysis verified the formation of nano-crystalline nanoconjugates. These nanoconjugates showed a remarkable catalytic activity in the range of 0.22–0.33 s−1 (varying with nanoconjugate concentration) which was much higher compared to conventional chemical methods of reduction. All the catalytic reaction experiments were performed at room temperature (27 ± 2 °C). Furthermore, an increase in rate constant was observed with increasing concentration of nanoconjugates. The catalytic activity of Au@CDs nanoconjugates was observed to be in order of m-nitrophenol > o-nitrophenol > p-nitrophenol with apparent rate constant (k aap) values of 0.068, 0.043 and 0.031, respectively. Comparative analysis with GNPs, CDs and Au@CDs nanoconjugates stated that the nanoconjugates had superior catalytic activity. The research can have significant implications in the development of new strategies for environmental remediation and biomedical applications.

Kinetic study of hydrate formation in CO2 + fruit Juice systems with application of Juice concentration

The utilization of gas hydrates technology for concentrating liquid foods has garnered significant interest in recent years. In this experimental study, we aimed to investigate the influence of various fruit juices, including cherry, pineapple, pomegranate, mango, grape, tomato, grapefruit, peach, lemon, orange, apple, and apricot juices, on the kinetic parameters of carbon dioxide hydrate formation. These investigations provide valuable insights into the industrialization potential of hydrate-based juice concentration processes. The kinetic experiments were conducted in a 460 cm3 reactor under an initial pressure of 3 MPa and a temperature of 275.65 K. Our findings reveal that the addition of fruit juices prolongs the induction time by up to 377 min compared to pure water, while reducing the CO2 uptake by 25.3%. Moreover, our results demonstrate variations in storage capacity (SC) among different fruit juices, with apple juice exhibiting the highest SC (31.74 v/v) and pineapple displaying the lowest (21.92 v/v). Furthermore, the apparent rate constant (kapp) values obtained during carbon dioxide hydrate growth indicate a slight increase in kapp for apple juice, while other juices exhibit a decrease in kapp, suggesting varying effects on hydrate growth kinetics. Our analysis suggests that concentration via CO2 hydrate may be particularly suitable for apple juice due to its promotional effect, whereas pineapple, apricot, and mango juices exhibit high inhibition influences on kinetic parameters, making them less recommended for concentration via CO2 hydrate formation.

Exfoliated MXene-AuNPs hybrid in sensing and multiple catalytic hydrogenation reactions.

The increasing use of nanomaterials in consumer products is expected to lead to environmental contamination sometime soon. As water pollution is a pressing issue that threatens human survival and impedes the promotion of human health, the search for adsorbents for removing newly identified contaminants from water has become a topic of intensive research. The challenges in the recyclability of contaminated water continue to campaign the development of highly reusable catalysts. Although exfoliated 2D MXene sheets have demonstrated the capability towards water purification, a significant challenge for removing some toxic organic molecules remains a challenge due to a need for metal-based catalytic properties owing to their rapid response. In the present study, we demonstrate the formation of hybrid structure AuNPs@MXene (Mo2CTx) during the sensitive detection of Au nanoparticle through MXene sheets without any surface modification, and subsequently its applications as an efficient catalyst for the degradation of 4-nitrophenol (4-NP), methyl orange (MO), and methylene blue (MB). The hybrid structure (AuNPs@MXene) reveals remarkable reusability for up to eight consecutive cycles, with minimal reduction in catalytic efficiency and comparable apparent reaction rate constant (Kapp) values for 4-NP, MB, and MO, compared to other catalysts reported in the literature.

Fabrication of magnetic biochar-MIL-68(Fe)-supported cobalt composite material toward the catalytic reduction performance of crystal violet

A magnetic biochar-MIL-68(Fe)-supported cobalt composite material (Co@MIL-68(Fe)@Fe3O4@CM-BC) was synthesized and used as a novel and effective catalyst for the catalytic reduction of crystal violet (CV) in aqueous environments. The prepared material was thoroughly characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and vibrating-sample magnetometer (VSM) techniques. Four operating parameters, including the CV dye concentration, time, catalyst dosage, and NaBH4 amount, were evaluated by employing central composite design (CCD) based on response surface methodology (RSM) for the catalytic reduction of CV. In the catalytic reduction of CV dye, the optimum conditions were determined as 15.67 mg/L CV dye concentration, 80.24 s time, 0.341 mg/mL catalyst dosage, and 14.56 mM NaBH4 amount with CV reduction efficiency of 99.98 %. The catalytic reduction kinetic of CV was studied by applying the pseudo-first-order model, and the apparent rate constant (kapp) values were obtained under different temperature (293–323 K). It was observed that kapp values increased upon increment of temperature. From kinetic studies, the activation energy was measured as 37.18 kJ/mol. Moreover, thermodynamic results showed that the activation entropy (ΔS#) and enthalpy (ΔH#) were obtained as −179.49 J/mol K and 34.62 kJ/mol, respectively. The thermodynamic parameters suggest that the catalytic reduction of CV was favorable and endothermic in nature. Regeneration tests indicated that the activity of Co@MIL-68(Fe)@Fe3O4@CM-BC was retained after five uses. Based on all of the results, the prepared material is a good candidate for the treatment of wastewater containing dyes like CV.

Photo-induced synthesis of star poly(DL-Lactide)-templated Au and Ag nanoparticles and evaluation of their catalytic performance

In this report, photochemical synthesis of monodispersed gold (Au) and silver (Ag) nanoparticles (NPs) was reported using cholic acid functionalized star poly(DL-lactide) (CA-(PDLLA)) as a capping and reducing agent. CA-(PDLLA) was synthesized by ring-opening polymerization (ROP) of DL-lactide with a feed ratio of 1:120 (cholic acid: DL-lactide). The molecular weight of CA-(PDLLA) was measured by using the gel permeation chromatography (GPC) technique. The thermal properties of the polymer and its nanocomposite materials were studied by thermogravimetric analysis (TGA). The optical properties of Ag and Au NPs were studied by UV–visible absorption spectroscopy. Morphological studies and size of the polymer-nanocomposites were assessed by using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques. The percentage composition of Au and Ag present in the polymer-nanocomposites was calculated using energy-dispersive X-ray spectroscopic (EDX) analysis. Finally, the synthesized polymer-metal nanocomposites were used as heterogeneous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction and the apparent rate constant (kapp) values of CA-(PDLLA)-AuNPs and CA-(PDLLA)-AgNPs were found to be 5.76 × 10−4 s−1 and 19.7 × 10−4 s−1, respectively.

Synthesis of one-dimensional hierarchical Bi2O3 with enhanced photocatalytic reduction of Cr(VI) and degradation of organic compounds under simulated sunlight

A one-dimensional (1D) hierarchical Bi2O3 is obtained by calcining hierarchical Bi2O2CO3. Hierarchical Bi2O3 exhibits good photocatalytic activity. Results show that 50 mg/L of Cr(VI) solution, 50 mg/L of tetracycline and 40 mg/L of biphenol A can be photodegraded in 10, 10 and 20 min under simulated sunlight with an apparent rate constant value of 0.331, 0.179 and 0.214 min−1, respectively. This enhanced photocatalytic performance is mainly ascribed to special hierarchical structure and the more negative CB position. Radical capture and EPR measurements all prove the superoxide (O2−) radical is the major active species for photocatalytic reaction. The transient photocurrent responses, PL emission and electrochemical impedance indicate 1D hierarchical Bi2O3 displays an improved separation efficiency of photogenerated e-h pairs. These findings would inspire many research for developing high-performance catalysts using under simulated sunlight.

Electrochemical enhanced heterogeneous activation of peroxymonosulfate by CoFe2O4 nanoparticles to degrade moxifloxacin

The catalytic mechanism of CoFe2O4 nanoparticles (NPs) was investigated in the system of electrochemical enhanced heterogeneous activation of peroxymonosulfate (EC/CoFe2O4/PMS) with moxifloxacin (MOX) as target contaminant. The removal efficiencies of MOX in PMS, CoFe2O4, EC, CoFe2O4/PMS, and EC/CoFe2O4/PMS system were 18.3%, 36.1%, 43.7%, 96.9%, and 98.3%, respectively. Although there was no synergy effect between EC and heterogeneous catalytic oxidation reaction (HCOR) on MOX removal, the value of apparent rate constant (karc) was much higher in EC/CoFe2O4/PMS system (0.24 min−1) compared with CoFe2O4/PMS system (0.13 min−1). Therefore, EC not only kept the structure of CoFe2O4 NPs stable, but also significantly accelerated the reaction rate of HCOR. Meanwhile, according to electrochemical impedance spectra of catalysts synthesized based on ion-substitution strategy and the EC-HCOR experimental results, the decisive role of Co in PMS activation and the electron transfer between Co and Fe were confirmed. The TOC removal efficiency was reached 74.4% as the ratio of PMS to CoFe2O4 NPs being 0.8 mM to 50 mg/L (30 min), and further improved to 87.6% with batch addition (0.25 mM per 30 min) of PMS (120 min, CoFe2O4 = 100 mg/L). The research results could improve the understanding of catalytic mechanism of spinel oxide in electrochemical system.

Insights into the cyclic voltammetry of surface-confined molecules undergoing two-electron transfers of any reversibility and any ordering of the formal potentials: Unravelling the apparent governing factors

The cyclic voltammetry (CV) of surface-immobilized electroactive species undergoing two-electron transfers (so-called surface EE mechanism) is comprehensively studied in this work, considering any electron transfer kinetics (k10′, k20′) and any values of their formal potentials (E10′, E20′). Hence, a large number of possible situations arise, which are systematized through the definition of apparent electrochemical rate constants for both electron transfers (which account for the combined effect of ki0′ (i=1,2), ΔE0′(=E20′−E10′) and the scan rate), with their values and ratio determining the features of the voltammetric signal.Guidelines are established for the elucidation of the reversibility of the process as a function of the relative values of such apparent rate constants, which reflects on the symmetry of the CV signals in the forward and reverse scans. Thus, as the second transfer is more favorable than the first one, kinetically and/or thermodynamically, the process behaves as more irreversible. Also, simple protocols of quantification of the corresponding kinetic and thermodynamic parameters are given on the basis of the analysis of the height, width, number and position of the CV peaks.

Ultra-fast photocatalytic degradation and seed germination of band gap tunable nickel doping ceria nanoparticles

Doping transition metal ions into cerium oxide (CeO2) results in interesting modifications to the material, including an increase in surface area, a high isoelectric point, biocompatibility, greater ionic conductivity, and catalytic activity. Herein, various concentrations (1–5%, 10% and 20%) of nickel (Ni) doped CeO2 nanoparticle have been made by a facile chemical process. Using a variety of cutting-edge analytical techniques, the structural, optical, and photocatalytic properties of undoped and varied concentrations (1–5%, 10%, and 20%) of Ni doped CeO2 nanoparticles have been investigated. Pure cubic fluorite structure with average crystallite sizes in the region of 12–15 nm was determined by X-ray diffraction (XRD) investigation. Transmission electron microscopy (TEM), which revealed highly homogeneous hexagonal shape of the particles with average size of 15 nm, was also used to determine microstructural information. According to the optical absorption, the band gaps of Ni doped and undoped CeO2 nanoparticles were found to be 2.96 eV and 1.95 eV, respectively. When exposed to sunlight, the narrow band gap Ni doped CeO2 nanoparticles worked as an active visible light catalyst to remove the dyes Rose Bengal (RB) and Direct Yellow (DY). The best photodegradation efficiencies for RB and DY dyes were found about 93% and 97%, respectively, using the 5% Ni-doped CeO2 catalyst. The apparent rate constant values of 0.039 for RB and 0.040 min−1 were attained for DY. As well, the treated, untreated dye solution and control solutions were utilized to assess the toxicity of commercially accessible Vigna Radiata seeds. In this study exhibits percentages of length and germination increased by 30–35% when compared to dye pollutant solution. The Ni doped CeO2 can provide a substantial alternative for current industrial waste management because of its quick photocatalytic activity and remarkable seed germination results.

Gamma radiation induced synthesis of double network hydrophilic cryogels at low pH loaded with AuNPs for fast and efficient degradation of Congo red

γ−radiation is a clean, fast and efficient synthetic route for polymeric materials. it is very powerful tool to generate free radicals during polymerization without any need of initiator and accelerator in both hydrophilic and hydrophobic media. Here in this work, for the first time, we fabricated acrylamide-methyl-propane sulfonic acid based-single and double network hydrophilic cryogels via γ−radiation at low pH. pH highly effects the synthesis of acrylamide-methyl-propane sulfonic acid based cryogels using redox initiation method. Along with pH, the effect of radiation time and radiation dose rate on cryo-polymerization was also studied. Gold hybrid cryogels (single and double network) were fabricated via self-reduction method at ambient conditions. Fourier transform infrared spectroscopy was implemented for chemical structure analysis of the synthesized material. The surface morphology of single and double network cryogels was observed via scanning electron microscopy. For the hybrid cryogels materials analysis x-ray diffraction, thermal gravimetric analysis, energy dispersive x-ray analysis, x-ray photoelectron spectroscopy and transmission electron microscopy and was used to confirm the presence of nanoparticles in the polymer network. The fabricated hybrid cryogels (0.15 g) were used for the degradation of Congo red (50 mL) as model dye in the presence of NaBH4 (0.02 g) with efficient and fast degradation activity. The apparent rate constant value (Kapp) for single and double network hybrid cryogels was 0.3652 min−1 and 0.2268 min−1, respectively. The activation energy, enthalpy and entropy was calculated (34.44 kJ.mol−1, –30.85 kJ.mol−1 and –146.30 J·mol−1k−1, respectively) using Arrhenius and Eyring equations for the fabricated catalyst. The catalyst was tasted in the tap water system and its efficiency was satisfied in real world too. The fabricated double wall hybrid catalyst will have a significant importance in the environmental field.

Effect of addition of surfactant on physicochemical properties of cobalt oxide nanoparticles synthesised using a domestic microwave: Applications as photocatalyst and supercapacitor

The present work highlights the comparison of the physicochemical properties of the metal oxide nanoparticles of cobalt synthesised using a domestic microwave in the presence and absence of surfactant. XRD analysis revealed that the addition of the surfactant was responsible for the reduction in the crystallite size of the metal oxide nanoparticles. SEM images showed more agglomeration in the case of surfactant-capped nanoparticles than the bare ones. The elemental composition obtained using EDAX of both nanoparticles showed a higher percentage of oxygen in the bare nanoparticles and better elemental stoichiometry in the surfactant-capped nanomaterials. The energy band gap calculated from the optical studies was higher in the case of surfactant-loaded nanoparticles than the bare ones. The photocatalytic studies of nanoparticles without and with surfactant showed 48 % and 40 % degradation of Methylene blue, respectively, in the presence of UV light with 1 g L−1 catalyst dose and 50 mg L−1 dye concentration at 300 min of irradiation time. Langmuir-Hinshelwood kinetic plots showed a marginally higher apparent rate constant value (2.22 × 10−3 min−1) for nanoparticles without surfactant than for nanoparticles with surfactant (2.11 × 10−3 min−1). The cyclic voltammograms of both the nanoparticles at a scan rate of 5 mV s−1 were faradic in nature and showed pseudo capacitance. The capacitance of nanoparticles with surfactant (166 F g−1) was found to be higher than that obtained for bare nanoparticles (111 F g−1). A comparison of the properties indicated that the addition of surfactant plays a vital role in tuning the properties of cobalt oxide nanoparticles for their specific application.

Synthesis of phytoextract-mediated Ag-doped graphitic carbon nitride (Ag@GCN) for photocatalytic degradation of dyes.

The present work focuses on the green synthesis of Ag-doped graphitic carbon nitride (Ag@GCN) for photocatalytic activities, which can contribute to a more sustainable environment. The leaf extract of the Ocimum tenuiflorum (Tulsi) plant was used to prepare the silver nanoparticles, as the plant extract serves as a stabilizing and capping agent in producing silver nanoparticles. Both Ag nanoparticles and urea-derived GCN were synthesized by thermal polymerization. The Ag-doped GCN nanocomposites were synthesized using various millimolar concentrations of Ag nanoparticles (NPs) with a fixed amount of GCN. The green nanocomposites (NCs) were synthesized by calcinating leaf extract at about 550°C. They were then characterized for surface morphology by SEM coupled with energy-dispersive X-ray spectroscopy (EDX), and elemental composition by XRD, Fourier-dispersive infrared spectroscopy (FTIR), and transmission electron microscope (TEM). Thermal stability and estimation of the Ag content in GCN were done through thermogravimetric analysis. The prepared series of nanocomposites (Ag-doped GCN 0.5mM, 1.0mM, 1.5mM, 2.0mM) were used to study the photocatalytic degradation efficiency of rose bengal (RB) and xylenol orange (XO) dyes. The degradation efficiency of dyes gets enhanced due to the doping of Ag nanoparticles into GCN. The efficiency increased from 54 to 76% and 15 to 36% in the case of RB and XO dyes, respectively. The apparent rate constant value increased up to 2.5 times in the case of the Ag-doped GCN (1.5mM) nanocomposite in comparison to GCN. The result obtained from the study confirmed that Ag-doped GCN (1.5mM) could act as a potential photocatalyst for wastewater remediation applications.

Synthesis and characterization of titanium-substituted nanocrystalline Co2-Y hexaferrite: magnetically retrievable photocatalyst for treatment of methyl orange contaminated wastewater.

Rapid industrial growth causes considerable environmental havoc, adversely affecting human and aqueous life. It becomes a significant concern to deal with adequate wastewater treatment strategies by converging on water scarcity. This research work explored the synthesis of titanium-substituted Y-type barium hexaferrite (Co2-Y), having a general formula of Ba2Co2Fe12-xTixO22 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5), using a facile nitrate-based sol-gel auto-combustion route and its suitability was investigated as a heterogeneous catalyst within the photo-Fenton-based degradation of methyl orange (MO), one of the significant pollutants generated from textile industries. Developing a thermochemically stable and magnetically separable heterogeneous catalyst for photocatalytic decomposition of nonbiodegradable organic dye from wastewater was also emphasized. The as-prepared nanocrystalline Co2-Y powders were analyzed using XRD, FTIR, DLS, UV-visible spectroscopy, SEM, VSM, and XPS. Furthermore, the photocatalytic degradation performance of pristine and titanium substituted Ba2Co2Fe11.6Ti0.4O22 ferrite, having the lowest bandgap value among all samples, was quantified and compared in terms of apparent rate constant (karc) value and turnover frequency values. The enriched photocatalytic performance was correlated with the existence of multi-valance states of transition metal cations and the availability of oxygen vacancy, confirmed by the surface chemistry using the XPS analysis. The modified (enhanced thermal and chemical stability) hexaferrite catalyst was magnetically separable and reusable without significant losses to its catalytic performance. This promising catalyst may be considered as a replacement for soft ferrite materials to catalyze the degradation of several other nonbiodegradable organic pollutants from wastewater in large-scale industries.

A New 2D Metal-Organic Framework for Photocatalytic Degradation of Organic Dyes in Water

Two-dimensional (2D) metal-organic frameworks (MOFs) are fascinating photocatalytic materials because of their unique physical and catalytic properties. Herein, we report a new (E)-4-(3-carboxyacrylamido) benzoic acid [ABA–MA] ligand synthesized under facile conditions. This ABA–MA ligand is further utilized to synthesize a copper-based 2D MOF via the solvothermal process. The resulting 2D MOF is characterized for morphology and electronic structural analysis using advanced techniques, such as proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and scanning electron microscopy. Furthermore, 2D MOF is employed as a photocatalyst for degrading organic dyes, demonstrating the degradation/reduction of methylene blue (MeBl) dye with excellent catalytic/photodegradation activity in the absence of any photosensitizer or cocatalyst. The apparent rate constant (kap) values for the catalytic degradation/reduction of MeBl on the Cu(II)–[ABA-MA] MOF are reported to be 0.0093 min−1, 0.0187 min−1, and 0.2539 min−1 under different conditions of sunlight and NaBH4. The kinetics and stability evaluations reveal the noteworthy photocatalytic potential of the Cu(II)–[ABA–MA] MOF for wastewater treatment. This work offers new insights into the fabrication of new MOFs for highly versatile photocatalytic applications.

Photocatalytic Activity and Reusability of F, Sm3+ Co-Doped TiO2/MWCNTs Hybrid Heterostructure for Efficient Photocatalytic Degradation of Brilliant Black Bis-Azo Dye

A global freshwater pollution catastrophe is looming due to pollutants of emerging concern (PECs). Conventional water treatment methods are limited in removing PECs such as pharmaceuticals and dye house effluent from aquatic systems. This study provides an effective potential solution by developing an innovative wastewater treatment method based on solar-light-responsive semiconductor-based photocatalysts. A sol-gel synthesis technique was used to produce Fluorine-Sm3+ co-doped TiO2 (0.6% Sm3+) (FST3) photocatalysts. This was followed by loading multi-walled carbon nanotubes (MWCNTs) in the range of 0.25 to 1 wt% into the FST3 matrix. Solid state UV-visible spectroscopy measurements showed a bathochromic shift into the visible light region after the co-doping of TiO2, whereas XRD analysis confirmed the presence of predominantly anatase polymorphs of TiO2. The FT-IR and EDX results confirmed the presence of the F and Sm3+ dopants in the synthesised photocatalysts. XRD and TEM measurements confirmed that the crystallite sizes of all synthesised photocatalysts ranged from 12–19 nm. The resultant photocatalysts were evaluated for photocatalytic degradation of Brilliant Black BN bis-azo dye in aqueous solution under simulated solar irradiation. FST3 completely degraded the dye after 3 h, with a high apparent rate constant (Ka) value (2.73 × 10−2 min−1). The degree of mineralisation was evaluated using the total organic carbon (TOC) technique, which revealed high TOC removal (82%) after 3 h and complete TOC removal after 4 h. The incorporation of F improved the optical properties and the surface chemistry of TiO2, whereas Sm3+ improved the quantum efficiency and the optical properties. These synergistic effects led to significantly improved photocatalytic efficiency. Furthermore, incorporating MWCNTs into the F and Sm3+ co-doped TiO2 (0.6% Sm3+) improved the reaction kinetics of the FST3, effectively reducing the reaction time by over 30%. Recyclability studies showed that after 5 cycles of use, the FST3/C1 degradation efficiency dropped by 7.1%, whereas TiO2 degradation efficiency dropped by 33.4% after the same number of cycles. Overall, this work demonstrates a sustainable and efficient dye-removal technique.

Synthesis, characterization, catalytic reduction of Eosin B dye and C, N cross coupling reactions of sodiumalginate/V2O5 nanocomposite

BackgroundA low cost with high efficiency sodiumalginate (SA)/V2O5 nanocomposite catalyst was synthesized by complexation followed by reduction method. The V2O5 catalyst and SA was chemically linked with each other and hence restriction in diffusion of the catalyst into the reaction medium during the course of the reaction. The catalytic activity of SA/V2O5 bio-nano catalyst system was tested towards the C, N cross coupling reaction and reduction of EB dye. MethodsThe bio-polymer nanocomposite formation was confirmed by FT-IR spectroscopy, 1H-NMR spectroscopy, DSC (Tg) and TGA (Td) and HR-TEM (size) like analytical tools. The cross coupling reaction between rosebengal (RB) and nitrogen containing heterocyclic compounds like indole, benzimidazole, 2-methylimidazole were carried out. Same type of reaction was carried out with congored (CR), acidfuchsin (AF) and safranine O (SO) dyes. Further, the catalytic activity of SA/V2O5 nanocomposite catalyst was tested towards the reduction of Eosin blue (EB) dye. Significant findingsThe FTIR spectrum showed a peak at 615 cm−1 due to the V-O stretching. The 1H-NMR spectrum confirmed that the OH group of SA involved in the complex formation with V atom of V2O5. The Tg and Td of the SA/V2O5 bio-polymer nanocomposite system was higher than that of the neat polymer. The apparent rate constant (kapp) value was found to be higher in the presence of SA/V2O5 catalyst system. The C,N cross coupling reaction was successfully carried out with significant % yield in the presence of low cost and eco-friendly SA/V2O5 nano catalyst. The catalyst was stable up to several cycles of operations.

Structural and Photocatalytic Studies on Oxygen Hyperstoichiometric Titanium-Substituted Strontium Ferrite Nanoparticles

Doping of ferrites is an important domain of research for their application as photocatalysts. In the present work, the effect of Ti4+ substitution on the structural and photocatalytic properties of strontium ferrite nanoparticles (NPs) is studied. Ternary doped Sr1−xTixFe2O4+δ ferrite NPs (x = 0.0–1.0) were synthesized by sol–gel methodology. Tetravalent Ti4+ ions caused oxygen hyperstoichiometry and enhancement in the surface area from 44.3 m2/g for SrFe2O4 NPs to 77.6 m2/g for Sr0.4Ti0.6Fe2O4+δ NPs. The average diameter of NPs ranged between 25–35 nm as revealed by TEM analysis. The presence of two sextets in the Mössbauer spectrum of pristine SrFe2O4 and Ti4+-substituted ferrite NPs and a paramagnetic doublet in the TiFe2O5 confirmed their phase purity. The photocatalytic potential of pure and Ti4+-substituted ferrite NPs was studied using nitroaromatic compounds, viz. pendimethalin, p-nitrophenol and Martius yellow, as model pollutants. Doped ferrite NPs with a composition of Sr0.4Ti0.6Fe2O4+δ NPs showed the highest degradation efficiency ranging from 87.2% to 94.4%. The increased photocatalytic potential was ascribed to the lowering of band gap (Eg) from 2.45 eV to 2.18 eV, a fourfold decrease in photoluminescence intensity, increased charge carrier concentration (4.90 × 1015 cm−3 to 6.96 × 1015 cm−3), and decreased barrier height from 1.20 to 1.02 eV. O2●− radicals appeared to be the main reactive oxygen species involved in photodegradation. The apparent rate constant values using the Langmuir–Hinshelwood kinetic model were 1.9 × 10−2 min−1, 2.3 × 10−2 min−1 and 1.3 × 10−2 min−1 for p-nitrophenol, pendimethalin and Martius yellow, respectively. Thus, tuning the Ti4+ content in strontium ferrite NPs proved to be an effective strategy in improving their photocatalytic potential for the degradation of nitroaromatic pollutants.

Oxidation of Cysteine by Electrogenerated Hexacyanoferrate(III) in Microliter Droplets.

Chemical reactivity in droplets is often assumed to mimic reactivity in bulk, continuous water. Here, we study the catalytic oxidation of cysteine by electrogenerated hexacyanoferrate(III) in microliter droplets. These droplets are adsorbed onto glassy carbon macroelectrodes and placed into an immiscible 1,2-dichloroethane phase. We combined cyclic voltammetry, optical microscopy, and finite element simulations to quantify the apparent bimolecular rate constant, kc,app, in microdroplets and bulk water. Statistical analyses reveal that the apparent bimolecular rate constant (kc,app) values formicrodroplets are larger than those in the continuous phase. Reactant adsorption to the droplet boundary has previously been implicated as the cause of such rate accelerations. Finite element modeling of this system suggests that molecular adsorption to the liquid|liquid interface cannot alone account for our observations, implicating kinetics of the bimolecular reaction either at the boundary or throughout the microliter volume. Our results indicate that cysteine oxidation by electrogenerated hexacyanoferrate(III) can be accelerated within a microenvironment, which may have profound implications on understanding biological processes within a cell.

Highly efficient removal of organic contaminant with wide concentration range by a novel self-cleaning hydrogel: Mechanism, degradation pathway and DFT calculation

A novel carbon nitride based self-cleaning hydrogel photocatalyst (KI-PCN gel, potassium and iodine co-doped carbon nitride confined in alginate) has been successfully constructed by a facile method. Fabricated photocatalyst showed enhanced synergistic adsorption-photocatalytic degradation property on a high concentration of methylene blue (HMB) because of enhanced carrier separation efficiency and improved light adsorption capacity of KI-PCN. As expected, the KI-PCN gel showed the highest apparent rate constant value (Kapp =0.0310 min−1), which was about 38.8 and 5.8 times as that of blank hydrogel (Kapp=0.0008 min−1) and PCN gel (Kapp=0.0053 min−1), respectively. Meanwhile, KI-PCN gel can continuously adsorb low concentration of MB (LMB), and the MB-adsorbed KI-PCN gel can self-clean under light irradiation. The bench-scale experiments simulating real river showed that KI-PCN gel can effectively and continuously remove LMB (0.1–20 ppm), indicating the possibility for the removal of contaminants in natural rivers. Furthermore, the possible degradation pathways were proposed by combining the density functional calculations (DFT) and intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This work proposed a new perspective to acquire a novel self-cleaning and easily recyclable photocatalyst for treatment of wide concentration range organic wastewater as well as remediation of natural waterbody.

Thermo‐sensitive ionic hydrogels synthesis via post quaternization cross‐linking: A highly efficient reusable catalytic thermo‐responsive nanoreactors

Radical polymerization reactions were employed to synthesize thermo‐responsive poly(N‐isopropylacrylamide‐co‐1‐vinylimidazole), p (NIPAM‐co‐VIm), hydrogels at room temperature. A postquaternized cross‐linking strategy was reported to fabricate thermo‐sensitive quaternized‐p (NIPAM‐co‐VIm) ionic hydrogels, Q‐p (NIPAm‐co‐VIm). Combination of methods (high‐resolution X‐ray photoelectron spectroscopy, dynamic light scattering, and atomic absorption spectroscopy) was employed to characterize the composite material. Following the concept of a “green chemistry,” the oxidation of alcohols/olefins was carried out in aqueous solution by using nanocomposites, p (NIPAM‐co‐VIm) and Q‐p (NIPAM‐co‐VIm). It was found that the catalytic activity of the metal nanocomposite can be modulated by the lower critical solution temperature (LCST) of particles. The catalyst showed improved catalytic activity above LCST. Quaternized composites showed higher catalytic activity than unquaternized counterparts, due to their high hydrophobicity, effective interactions between substrates and catalyst, and high flexibility. In addition, we demonstrated that the catalytic activity of the nanocomposites can be tuned by the volume phase transition within the hydrogel by using the catalytic reduction of 4‐nitrophenol/nitrobenzene, NP/NB, as the hydrophilic/hydrophobic substrates model. For 4‐NP, with an increase in temperature from 25°C to 35°C (<LCST), the apparent rate constant values had a downward trend. On the contrary, for NB, this value had an upward trend. These results revealed that different changes in rate constant for 4‐NP and NB with temperature should be attributed to significant differences in NP/NB affinity to interact with Ag‐NPs in the hydrogel. Moreover, the catalysts could efficiently be recycled four times without losing their quality. FT‐IR spectra and atomic absorption spectroscopy also proved that the catalysts were recyclable, durable, and leaching‐resistant.