H2O Solvent Research Articles

Fluorescent PVP-g-chitosan polymer probes for the recognition of 4-nitrophenol

Natural polymer chitosan has many advantages, but the poor solubility limits its application. In this study, chitosan derivatives soluble in DCM, DMF, DMSO, H2O and other solvents were developed by introducing side chains into chitosan (CS). In addition, the fluorescent group on the side chain makes the chitosan derivative have the ability to detect 4-nitrophenol (4-NP). Firstly, a chain transfer agent containing C C (N3-NS) was synthesized with naphthalimide as the fluorescence unit. Then, using AIBN as initiator, an extensively soluble polymer with fluorescent moiety TP-NVP was synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT) method using monomer N-vinyl pyrrolidone (NVP). Finally, the C C of TP-NVP was used to react with –NH2 on CS to prepare PVP-g-chitosan, so that more CS was “pulled” by TP-NVP into the solvent. The solubility of the synthesized CS-PVP probe can be adjusted by adjusting the amount of NVP, up to 17.6 mg/mL. At the same time, the synthesized CS-PVP had a good detection effect on 4-NP, and the detection limit (LOD) was 0.054 μM. The HOMO-LUMO energy level of the probe was calculated by cyclic voltammetry (CV). In addition, CS-PVP was successfully loaded on a low background fluorescent test paper to achieve real-time visual intelligent determination of 4-NP in real samples with the help of a color scanning APP of a smartphone.

Strong Red Luminescence in Europium Complexes Solution for Anti-Counterfeiting Applications.

Eu3+-activated phosphors with distinct photoluminescence properties are well-suited for diverse applications, including lighting, sensing, and imaging. Despite their potential, the large-scale and energy-efficient production of Eu3+-doped phosphors remains a significant challenge for industrial applications. This research delves into the luminescent performance of Eu3+ ions in nitrate solutions at room temperature by employing detailed spectroscopic characterization. Results reveal vibrant red luminescence at 594 nm and 616 nm in europium nitrate solutions, irrespective of concentration or solvent. We proposed a luminescent mechanism based on the formation of coordination complexes in nitrate solution. Furthermore, the investigation highlights the superior performance of NH2- over CH2-ligands in mitigating the deactivation of Eu3+ emissive state induced by OH- oscillators in H2O solvent, leading to enhanced photoluminescence. Particularly, europium nitrate solutions without lengthy preparation exhibit ligand-dependent luminescent feature, showcasing potential applications in anti-counterfeiting and coordination group structure detection. This study here not only enhances our understanding of rare earth luminescence mechanisms, but also broadens the range of rare earth luminescent materials.

Effect of solvent in the solvothermal synthesis of nickel(II)-terephthalate complex

This research aims to replace the use of dimethylformamide (DMF) with a greener solvent in the solvothermal synthesis of nickel(II)-terephthalate complex. Effect of solvent on the crystallinity degree, thermal stability, and band gap energy of the synthesized complex are also studied. The synthesis was carried out using solvothermal method at 150 0C for 10 hours with a Ni(II) : terephthalate acid mol ratio of 1:1 in several H2O:DMF solvent compositions (1:0; 1:1; and 0:1). The precipitated products underwent characterization using ATR-IR, P-XRD, SEM, TGA, Surface Area Analyzer, and UV-DRS. Findings revealed the successful formation of the Ni(II)-terephthalate complex using three different solvent compositions (H2O/DMF = 1:0, 1:1, and 0:1). This suggests that the complex can be synthesized using more environmentally friendly solvents, potentially reducing or substituting the use of DMF solvent. However, the solvent affects the characteristics of the synthesized complex, in which green block microcrystalline solid was obtained when using water as the solvent, meanwhile green aggregates with lower crystallinity degree was precipitated out when using DMF or H2O-DMF. The Ni(II)-terephthalate complexes obtained from the H2O and H2O-DMF solvents are different to that of from the DMF solvent, but they both has identical powder diffraction pattern with previously reported compound of [Ni3(OH)2(C8H4O4)2(H2O)4].2H2O. Furthermore, the use of water as the solvent increase the crystallinity degree and thermal stability of the complex but the band gap energy of the synthesized Ni(II)-terephthalate complex compared to that of obtained from the DMF solvents.

Aptamer-Based Electrochemical Biosensing Platform for Analysis of Cardiac Biomarkers.

Monitoring biomarkers secreted by cardiomyocytes is critical to evaluate anticancer drug-induced myocardial injury (MI). Cardiac troponin I (cTnI) is considered the gold standard biomarker for MI. Herein, an electrochemical aptasensor is engineered for cTnI detection based on lanthanide europium metal-organic frameworks (Eu-MOFs) and a hybridization chain reaction-directed DNAzyme strategy. Three types of Eu-MOF morphologies were easily synthesized by changing the solvent, and the Eu-MOF modulated by mixing the solvent of dimethylformamide and H2O (D-Eu-MOF) exhibited the best performance compared to other morphologies of the Eu-MOFs. Multifunctional nanoprobes were constructed from D-Eu-MOF@Pt loaded with natural horseradish peroxidase and combined with an aptamer-initiated nuclear acid hybridization chain reaction to form G-quadruplex/hemin DNAzymes for signal amplification. A novel capture probe is constructed on the basis of DNA nanotetrahedrons modified on screen-printed gold electrodes to enhance the capture of the target and multifunctional nanoprobes for signal amplification. It exhibits a detection limit of 0.17 pg mL-1 and a linear range from 0.5 pg mL-1 to 15 ng mL-1. The practicality of the platform is evaluated by measuring cTnI in real samples and secreted by cardiomyocytes after drug treatment, which provides great potential in drug-induced MI evaluation for clinical application.

Ag nanoparticles on arginine-cyanoguanidine functionalized magnetic g-C3N4: A catalyst for nitroaromatic hydrogenation and regioselective click reactions

This study describes the development of a novel hybrid nanocatalyst that was obtained by doping magnetic g-C3N4 with Ag nanoparticles and modifying it with arginine and cyanoguanidine (Ag@Fe3O4-g-C3N4-Arg-CG). Comprehensive characterization of the nanocatalyst using techniques such as FTIR, XRD, SEM, and TGA confirmed its structural and morphological properties. The catalytic efficiency of the synthesized nanostructure was evaluated in two key reactions: the reduction of nitroaromatic compounds and a click reaction for 1,2,3-triazole synthesis. The results demonstrate that Ag@Fe3O4-g-C3N4-Arg-CG effectively reduced various nitroaromatic compounds to substituted anilines at room temperature using NaBH4 as the reducing agent. Nitrobenzene reduction did not proceed in aprotic solvents such as acetonitrile, CH2Cl2, and dimethylformamide, whereas it exhibited a high reaction yield in protic solvents such as ethanol and water. The highest yield (100 %) was observed in water at 50 °C using H2O solvent. Additionally, the nanohybrid exhibited significant potential for “green” click chemistry by efficiently synthesizing 1,2,3-triazoles under mild conditions, with low catalyst loading. Its magnetic properties facilitated easy recovery, and the catalyst maintained high activity over six cycles, making it suitable for sustainable applications in organic transformations.

Green synthesis of cobalt oxide nanoparticles (Co3O4NPs): Characterization and green light-driven photocatalytic aerobic oxidation of alkyl and aryl sulfides to the corresponding sulfoxides

In recent years, cobalt oxide nanoparticles (Co3O4NPs) have garnered significant attention due to their unique properties and wide range of applications, particularly in catalysis and environmental remediation. This study focuses on the green synthesis of Co3O4NPs using garlic extract as a bio-reducing and stabilizing agent, marking the first instance of employing this eco-friendly and cost-effective method. The synthesized nanoparticles were characterized using various techniques including SEM, EDX, FTIR, XRD, UV–Vis DRS, and BET analysis, revealing their spherical morphology, elemental composition, surface area, and optical properties. The primary application investigated was the photocatalytic aerobic oxidation of alkyl and aryl sulfides to sulfoxides under visible green light irradiation. The study meticulously optimized the reaction conditions, evaluating the effects of different solvents, light sources, and catalyst dosages. The optimal conditions were found to be a MeCN:H2O (5:1) solvent system, green LED light (535 nm), and 10 mg of Co3O4NPs catalyst with the highest TON of 12.5. Under these conditions, the catalyst demonstrated high efficiency, achieving up to 95% yield of sulfoxides with various substrates. Furthermore, the reusability of the Co3O4NPs was assessed through multiple catalytic cycles, showing excellent stability and consistent performance. Mechanistic studies indicated that the photocatalytic activity involves the generation of reactive oxygen species (ROS) such as superoxide anion radicals (O2.-) and singlet oxygen (1O2), with both holes and electrons playing crucial roles in the oxidation process. This research highlights the potential of green synthesized Co3O4NPs as effective and sustainable photocatalysts for selective oxidation reactions, offering a promising approach for environmentally benign chemical processes. The findings pave the way for further exploration of bio-derived catalysts in various industrial applications, promoting greener and more sustainable practices in chemical synthesis.

Computational study on the Maillard reactions of glucose and galactose with lysine.

Milk has nutrient-rich but thermal sensitive matrix that undergoes varying degrees of Maillard reaction (MR) at heating conditions. The MR mainly occurs between lysine residues (Lys) and lactose composed of glucose (Glc) and galactose (Gal), which are abundantly sourced from dairy products. In the present study, the MRs of Glc and Gal with Lys at the initial and intermediate stages have been investigated theoretically using density functional theory (DFT) to simulate the gaseous and aqueous phases. Reaction mechanisms have been proposed, and relative energy changes of different steps were calculated according to the total mass balance. The calculations reveal that both Nα- and Nε-amine groups of Lys can react with the carbonyl functional group of Glc and Gal with the similar potential energy profiles, and Gal is more reactive than Glc. However, the barrier in Nε-channel is lower than in Nα-channel, indicating a faster reaction rate through the former channel compared with the latter. The 5-hydroxymethyl-2-furfural (HMF) and derivative are formed under 3-deoxysone route in the intermediate stage. The calculation results are helpful for proposing a reasonable MR mechanism and suggesting possible control methods of the MRs. In this study, different levels of DFT calculations have been conducted to investigate the mechanisms and favorability of generating MR products in Glc-Lys and Gal-Lys models at initial and intermediate stages in the gaseous and aqueous conditions. In order to elucidate the molecular models from the perspectives of chemistry and geometry, DFT calculations were performed by the mean of B3LYP functional at basis sets of 6-311 + + G (d, p) and 6-311 + + G (2df, 2p) with optional solvation settings. To examine the solvation effect, the study further constructed models with solvent H2O and calculated in wB97XD functional with 6-31 + G (d) basis set. All computations were carried out Gaussian 09 suite of quantum chemistry software.

Pyrazine-based supramolecular photosensitizing assemblies as type I photosensitizers for high-efficiency photooxidation reactions

Donor-acceptor thermally activated delayed fluorescent (TADF) materials have been widely used in photocatalytic reactions as organic photosensitizers. However, the construction of TADF photosensitizers via a supramolecular self-assembly approach with the regulation of reactive oxygen species (ROS) is still a big challenge. In this study, a TADF molecule 4,4'-(6-(pyridin-4-yl)quinoxaline-2,3-diyl)bis(N,N-diphenylaniline) (TPA-PQ) by incorporating triphenylamine (TPA) act as donor and 6-(pyridin-4-yl)quinoxaline (PQ) act as an acceptor was designed and synthesized, which exhibited excellent TADF property and strong intramolecular charge transfer. Meanwhile, the TPA-PQ can not only self-assemble to form nanofiber structure in mixed solvent of H2O and THF, but also can be used as a type I photosensitizer to selectively produce superoxide anion radicals (O2•–). More interestingly, the ROS generated from TPA-PQ can be used as photocatalysts for the oxidative hydroxylation of arylboronic acids and aerobic cross dehydrogenation coupling (CDC) reactions with high yields of 92 % and 88 %, respectively. This study presents an innovative and eco-friendly approach to utilize TADF supramolecular structures for the purpose of conducting photocatalyzed organic reactions.

Development of a triazole-linked bis-organosilane compound as dual-function agent: Sensing of Al3+ ion in aqueous environments and inhibition of HIV-1 protease

The increasing applications of aluminum metal have led to rising concerns regarding its adverse environmental impacts, particularly on marine life and human health, necessitating its efficient detection. Bis-organosilane compounds hold a pivotal position in organosilicon chemistry, contributing significantly to industrial processes and scientific research. In this study, a synthesized bis-1,2,3-triazole-linked bis-organosilane was employed as a sensor for the selective detection of Al³⁺ ions in a MeOH: H₂O (7:3, v/v) solvent system. This sensor demonstrated high selectivity and strong anti-interference capabilities, even in the presence of other metal ions. The detection limit for Al³⁺ was found to be significantly lower than the WHO-prescribed limits for drinking water. Using an actual water sample analysis experiment, its practical utility was also investigated. Additionally, bis-organosilane (6) capability as an antioxidant to stabilize free radicals was also tested. Given the biological significance of triazoles, compound (6) was evaluated for its inhibitory activity against HIV-1 protease using molecular docking tools. the current study emphasizes bis-organosilane (6) as an Al3+ sensor with dual activity as a possible HIV medication and a significant antioxidant.

Insight into adsorption-desorption of methylene blue in water using zeolite NaY: Kinetic, isotherm and thermodynamic approaches

It is critical to find an efficient method to separate methylene blue (MB) in wastewater before discharging them into environment. Adsorption using zeolites is the most commonly used one. To determine adsorption mechanism providing useful data to enhance adsorption capacity and practicability of scale-up, kinetic, isotherm and thermodynamic adsorption were evaluated and discussed intensely. Zeolite NaY was synthesized from rice husk ash with a one-stage process. Effects of pH, contact time, initial concentration, adsorbent dose, temperature, solvents and recyclic stability on MB adsorption and desorption were investigated in detail via alternating variable method. Optimal conditions for adsorption were at pH 8, 1 h, 50 mgMB/L, 303K. Adsorption kinetics and isotherms showed that the process fitted to pseudo-second-order, Freundlich and Temkin isotherm, indicating a spontaneous, exothermic and physical adsorption process with multilayer adsorption. Desorption process showed that EtOH:H2O (1:1) solvent at 323K was optimal for releasing MB and its thermodynamic studies revealed that this process was favorable with rising temperature. The maximum adsorption capacity was calculated as 49 mg/g and the adsorbent could maintain its adsorption performance after six cycles. Generally, this study provided a comprehensive approach of an efficient, cost-effective, and recyclable NaY for MB removal from water.

Indole-derivative β-diketone samarium and terbium compounds modified by ancillary ligand: Syntheses, crystal structures, and photoluminescence properties

EIFD, LnCl3·6H2O (Ln = Sm, Tb) and ancillary ligand are developed to synthesize a sequence of six new β-diketone Sm-based and Tb-based compounds modified to enhance the photoluminescence property, namely Sm(EIFD)3(H2O)·CH2Cl2 (1), Sm(EIFD)3(bpy) (2), Sm(EIFD)3(phen)·CH2Cl2 (3), Tb(EIFD)3(H2O)·CH2Cl2 (4) and Tb(EIFD)3(bpy) (5), Tb(EIFD)3(phen)·CH2Cl2 (6) (EIFD: 1-(1-ethyl-1H-indol-3-yl)-4,4,4-trifluorobutane-1,3‑dione, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The crystal structures of compounds 1−6 with the lanthanide(III) ions of seven (1, 4)/eight (2, 3, 5, 6) coordinated configuration are determined by single-crystal X-ray diffraction. Different non-covalent interactions (NCIs) and their% contribution to the compounds structures and their roles in stabilizing the structure are determined by Hirshfeld surface analysis. The photoluminescence properties of compounds 1−6 by substituting the solvent H2O with bpy and phen contained nitrogen ancillary ligands are then studied experimentally, leading to a rationalization of their central lanthanide(III) ions emission lifetime.

A phenanthridine-based fluorescent sensor for selective ratiometric detection of BF3 with AIE properties and applications in environmental monitoring

In this work, we report the synthesis of 5-(4-(pyridine-4-yl)phenyl)-7,8,13,14-tetrahydrodibenzo[a, i]phenanthridine (SP23), a phenanthridine-based chemosensor, by applying the Mannich reaction process. The starting components for this reaction were 2-tetralone, aromatic aldehyde, and ammonium acetate. Several spectroscopic investigations including 1H NMR, and HRMS were used to confirm the synthesized chemosensor SP23. In the ACN:H2O (9:1) solvent mixture, SP23 is more sensitive and selective to BF3 than the other competing ions. It is interesting to note that a ratiometric emission shift changes from blue to yellow fluorescence was observed with the BF3 ion. The detection limit of 7.58 nM was discovered using this chemosensor, which was less than the previous findings. After administering triethylamine as a regenerating material to the BF3 complex, the SP23 could be made reversible. Furthermore, the aggregation investigations indicate that the Aggregation Induced Emission (AIE) phenomenon was followed by the Aggregation Caused Quenching (ACQ) phenomenon. Ultimately, a paper-based test kit was constructed, using the established chemosensor, for practical usage.

Probing Short-Range Interactions in Isostructural Hydrate and Perhydrate of Dabrafenib by Magic-Angle Spinning Solid-State NMR.

Dabrafenib (DBF), an anticancer drug, exhibits isostructural properties in its hydrate (DBF⊃H2O) and perhydrate (DBF⊃H2O2) forms, as revealed by single-crystal X-ray diffraction. Despite the H2O and H2O2 solvent molecules occupying identical locations, the two polymorphs have different thermal behaviors. In general, determination of stoichiometry of H2O in the perhydrate crystals is difficult due to the presence of both H2O and H2O2 in the same crystal voids. This study utilizes magic-angle spinning (MAS) solid-state NMR (SSNMR) combined with gauge-included projector augmented wave calculations to characterize the influence of solvent molecules on the local environment in pseudopolymorphs. SSNMR experiments were employed to assign 1H, 13C, and 15N peaks and identify spectral differences in the isostructural pseudopolymorphs. Proton spectroscopy at fast MAS was used to identify and quantify H2O2/H2O in DBF⊃H2O2 (mixed hydrate/perhydrate). 1H-1H dipolar-coupling-based experiments were recruited to confirm the 3D molecular packing of solvent molecules in DBF⊃H2O and DBF⊃H2O2. Homonuclear (1H-1H) and heteronuclear (1H-14N) distance measurements, in conjunction with diffraction structures and optimized hydrogen atom positions by density functional theory, helped decipher local interactions of H2O2 with DBF and their geometry in DBF⊃H2O2. This integrated X-ray structure, quantum chemical calculations, and NMR study of pseudopolymorphs offer a practical approach to scrutinizing crystallized solvent interactions in the crystal lattice even without high-resolution crystal structures or artificial sample enrichment.

Triply Interlocked [2]catenanes: Rational Synthesis, Reversible Conversion Studies and Unprecedented Application in Photothermal Responsive Elastomer

AbstractTriply interlocked [2]catenane complexes featuring two identical, mechanically interlocked units are extraordinarily rare chemical compounds, whose properties and applications remain open to detailed studies. Herein, we introduce the rational design of a new ligand precursor, L1, suitable for the synthesis of six triply interlocked [2]catenanes by coordination‐driven self‐assembly. The interlocked compounds can be reversibly converted into the corresponding simple triangular prism metallacage by addition of H2O or DMF solvents to their CH3OH solutions, thereby demonstrating the importance of π⋅⋅⋅π stacking and hydrogen bonding interactions in the formation of triply interlocked [2]catenanes. Moreover, extensive studies have been conducted to assess the remarkable photothermal conversion performance. Complex 6 a, exhibiting outstanding photothermal conversion performance (conversion efficiency in solution : 31.82 %), is used to prepare novel photoresponsive elastomer in combination with thermally activated liquid crystal elastomer. The resultant material displays robust response to near‐infrared (NIR) laser and the capability of completely reforming the shape and reversible actuation, paving the way for the application of half‐sandwich organometallic units in photo‐responsive smart materials.

Triply Interlocked [2]catenanes: Rational Synthesis, Reversible Conversion Studies and Unprecedented Application in Photothermal Responsive Elastomer.

Triply interlocked [2]catenane complexes featuring two identical, mechanically interlocked units are extraordinarily rare chemical compounds, whose properties and applications remain open to detailed studies. Herein, we introduce the rational design of a new ligand precursor, L1, suitable for the synthesis of six triply interlocked [2]catenanes by coordination-driven self-assembly. The interlocked compounds can be reversibly converted into the corresponding simple triangular prism metallacage by addition of H2O or DMF solvents to their CH3OH solutions, thereby demonstrating the importance of π⋅⋅⋅π stacking and hydrogen bonding interactions in the formation of triply interlocked [2]catenanes. Moreover, extensive studies have been conducted to assess the remarkable photothermal conversion performance. Complex 6 a, exhibiting outstanding photothermal conversion performance (conversion efficiency in solution : 31.82 %), is used to prepare novel photoresponsive elastomer in combination with thermally activated liquid crystal elastomer. The resultant material displays robust response to near-infrared (NIR) laser and the capability of completely reforming the shape and reversible actuation, paving the way for the application of half-sandwich organometallic units in photo-responsive smart materials.

Molecular dynamics simulation on crystal morphology of NH4ClO4.

Ammonium perchlorate (NH4ClO4, abbreviated as AP) has the advantages of high oxygen content, high density, and good compatibility, and has significant application prospects in the field of energetic materials. The crystal morphology has a great influence on the properties and sensibility of energetic materials, and a single experimental means is difficult in exploring the crystals; therefore, the crystal morphology of AP is investigated using molecular dynamics simulation complemented with experiments, to theoretically analyze the differences in AP crystal habit and the interactions between solvent molecules and the main growing crystal surfaces of AP. The results show that AP crystal is mainly composed of five independent crystal surfaces (0 0 1), (0 1 0), (1 0 0), (1 0 1), and (1 0 -1) in vacuum using the BFDH laws, with (0 0 1) surface being the main growth crystal surface. In contrast, in H2O solvent, the (1 0 1) and (1 0 -1) surfaces disappear, and the AP mainly consists of (0 0 1), (0 1 0), and (1 0 0) surfaces with a rectangular shape. The crystal morphology obtained from theoretical prediction is in good agreement with that obtained from experimental culture. This paper can provide a new idea for the cultivation and preparation of AP large crystals, and promote the application of AP crystals in energetic materials. The crystal morphologies of AP in vacuum and H2O solvent under Dreiding force field were predicted based on attachment energy model by using molecular dynamics method in Materials Studio 2019 software. The entire molecular dynamics simulation was carried out under the NTV system, the temperature control method was selected as Anderson, and the system temperature was set to 298 K. The simulation time was set to 40 ps, the step size was set to 1 fs, and the data were outputted every 5000 steps.

Comparative Linkage of Novel Anti-Tumor Pd(II) Complex with Bio-Macromulecules: Fluorescence, UV-Vis, DFT, Molecular Docking and Molecular Dynamics Simulation Studies.

A novel mononuclear palladium complex, [Pd(dach)(SSA)], where dach and SSA are diaminocyclohexane and sulfosalicylic acid ligands, respectively, has been synthesized and identified utilizing analytical and spectral methods. DFT calculations, namely geometry optimization, MEP, HOMO-LUMO and NBO analysis, have been conducted at B3LYP level by aug-ccpVTZ-PP and 6-311G(d, p) basis sets. NBO and HOMO-LUMO analysis exhibited that the palladium compound is stable. MEP showed the potential sites of molecule for the interaction. By employing MTT assay, the cytotoxicity activity of the aforesaid compound was examined on K562 cell line, which revealed a proper activity compared to cisplatin. To ascertain the lipophilicity of the newly made compound, the partition coefficient measurement was accomplished, which follows the order of cisplatin < Pd(II) complex. Next, investigation of binding properties of the studied compound with DNA of calf thymus and BSA were done by spectroscopic (CD, fluorescence emission and electronic adsorption) and non-spectroscopic (viscosity measurements, DNA gel electrophoresis, molecular docking and molecular dynamics simulation) methods. The outcomes of CD and UV-Vis spectroscopy demonstrated that the title compound refolded the protein via increasing the alpha helix percentage. The data obtained from UV-Vis studies indicated the non-intercalative mutual action between Pd(II) complex with DNA. It also revealed that the Kapp magnitude of CT-DNA (7.43 × 104 M- 1) is higher than the BSA (5.17 × 103 M- 1), and L1/2 (midpoint of transition) of CT-DNA (5 µM) is lower than the BSA (5.7 µM), indicating that the complex has a greater binding affinity to CT-DNA than BSA. Fluorescence quenching mechanism of the two biomolecules by the metal complex is static and the calculated thermodynamic parameters (ΔS° < 0 and ΔH° < 0) suggested the hydrogen bonding and/ or van der Waals forces with DNA and BSA. Further, molecular docking indicated that the studied compound fits into the groove of DNA and the site I of BSA. The stability of metal compound-DNA/-BSA in the presence of H2O solvent and over the time were validated via molecular dynamics simulation.

Interaction between methyl red and cetyltrimethylammonium bromide under the influence of sodium polystyrene sulphonate in ethanol-water binary solvent systems: A spectrophotometric investigation

This research aims to comprehensively investigate and analyze the UV–visible spectroscopic behavior of the methyl red (MR)-cetyltrimethylammonium bromide (CTAB) system under the influence of sodium polystyrene sulfonate (NaPSS) in aqueous and different volume fractions (v.f.) of ethanol (EtOH)–H2O (0.1, 0.2, and 0.3) at 298.15 ± 0.2 K. In EtOH–H2O solvent systems, the triple interactions of dyes-surfactants-polyelectrolyte (DSP) complex systems are entirely novel. MR interacts with CTAB in NaPSS in the binary solvent media (0.1, 0.2, and 0.3 v.f. of EtOH–H2O) resulting in the formation of ion-pairs at very low CTAB concentrations, far below their apparent critical micelle concentration (CMC*) reducing the absorbance, and the new complexes above the CMC* due to solubilization of the MR into CTAB micelles observed by distinct spectral shifts. The CMC* values obtained from spectroscopic data increase in the order: (CMC*)water< (CMC*)0.1< (CMC*)0.2< (CMC*)0.3. This is because of the reduced polarity or dielectric constant and increased degree of water structure disruption around the hydrophobic chains of CTAB, where micelle formation occurs at somewhat higher concentrations. The Gibbs energy of micellization (ΔGmo) increases in the order: (ΔGmo=−16.89)water <(ΔGmo=−16.17)0.1<(ΔGmo=−15.62)0.2<(ΔGmo=−15.38)0.3, which further supports the inhibitory effect of increasing ethanol content towards micellization. In the post-micellar region, the decrease in hydrophobic interactions and an increase in electrostatic interactions lead to a rise in the overall binding constant value. This means that, when NaPSS is present, the stronger electrostatic interactions in the post-micellar region contribute significantly to the increased binding of CTAB micelles with MR. The tautomeric activity of MR and the solvent composition played a prime role in affecting the interaction mechanism, as evidenced by the blue and red spectral shifts.

Valence band XPS spectra of K silicate glasses: Effect of HOMO energies on K, Na and Li leach rates, activation energies and reaction mechanism

X-ray Photoelectron spectra of K-silicate glass valence bands (VBs) are composed of distinct upper and lower bands, separated by a minimum at ∼10 eV binding energy. A third, narrow band at ∼4.5 eV represents the highest energy occupied molecular orbitals (HOMOs). Na and Li glass VBs are similarly composed of upper, lower and HOMOs bands. The HOMOs reside only on NBO atoms (NBO = O atoms of the Si-O-M moiety; M = alkali), are non-bonding orbitals of O 2py character and are located at 4.5, 4.8 and 5.2 eV in K, Na and Li glasses. The order corresponds to alkali leach rates in water. We propose a SN reaction mechanism and Frontier Molecular Orbital concepts for leaching involving the HOMOs of the glasses and the LUMO of an adsorbed water molecule. The activated complex, Si-NBO*-M (NBO* = NBO•••HO-H), is formed through H-bonding of a solvent H2O molecule to NBO.

Influences of fractional separation on the structure and reactivity of wheat straw cellulose for producing 5-hydroxymethylfurfural

High-efficient production of 5-hydroxymethylfurfural (HMF), a “sleeping giant” in sustainable chemistry, from cellulose depends significantly on the effective separation of cellulose from lignocellulosic biomass. Herein, we report the fractional separation of wheat straw cellulose (WSC) from wheat straw under solvothermal conditions using a mixed solvent of γ-valerolactone (GVL) and H2O as the separating solvent, wherein the impacts of fractional separation parameters (solvent composition, temperature, and time) on removals of lignin and hemicellulose as well as purity and recovery of cellulose were studied by a Box-Behnken Design of response surface method. The optimization of the solvothermal parameters enabled an optimal fractional separation condition (VGVL: ∼ 60.0 vol%, T: 205 oC, t: ∼1.7 h) that led to a higher purity (89.4%) and recovery (86.7%) of cellulose in WSC. A further correlation of the removals of lignin and hemicellulose as well as purity and recovery of cellulose with the yield of HMF excluded an independent influence of the above factors. Instead, a comprehensive contribution of high fractional separation efficiency (defined as the product of cellulose purity and recovery) and low crystallinity of WSC was found to improve the HMF yield. However, the heat- and freeze-dryings of WSC after the solvothermal separation were found to lower the HMF yield because it re-improved the crystallinity of WSC. A high HMF yield of 58.6 mol% was achieved after reacting wet-WSC in a mixed solvent of 1,4-dioxane and H2O at 180 oC for 20 min, which was 1.5 fold higher than that from microcrystalline cellulose. This work highlights the importance of enhancing the fractional separation efficiency of cellulose from lignocellulosic biomass whereas avoiding drying process for future HMF biorefinery.