Polar Solvents Research Articles

Extending Shelf-Life of Two-Step Method Precursor Solutions through Targeted Regulation for Highly Efficient and Reproducible Perovskite Solar Cells.

Precursor solution aging process can cause significant influence on the photovoltaic performance of perovskite solar cells (PVSCs). Notably, we first observe that the aging phenomenon is more severe in the precursor of two-step sequential method compared to that in one-step method due to that the protic solvent isopropanol facilitates amine-cation side reaction and iodide ions oxidation. Herein, we report a novel approach for selectively stabilizing both organic amine salt and lead iodide (PbI2) precursor solutions in two-step method. The introduction of benzene-1,3-dithiol into organic amine salt solution can mitigate amine-cation side reactions due to the formation of an acidic and reducing environment. Simultaneously, decamethylferrocene (FcMe10/FcMe+ 10) pair can act as a redox shuttle in PbI2 solution to concurrently oxidize Pb0 and reduce I2 in cyclic manner. Consequently, the PVSCs device fabricated from ameliorative precursor solutions demonstrates superior power conversion efficiency of 25.31 %, retaining 95 % of its efficiency after 21 days of solution aging. Moreover, the unencapsulated devices maintain 85 % of primitive efficiency for 1500 h at maximum power point tracking under continuous illumination. This work establishes a fundamental guidance and scientific direction for the stabilization of two-step perovskite precursor solutions.

Extending Shelf‐Life of Two‐Step Method Precursor Solutions through Targeted Regulation for Highly Efficient and Reproducible Perovskite Solar Cells

AbstractPrecursor solution aging process can cause significant influence on the photovoltaic performance of perovskite solar cells (PVSCs). Notably, we first observe that the aging phenomenon is more severe in the precursor of two‐step sequential method compared to that in one‐step method due to that the protic solvent isopropanol facilitates amine‐cation side reaction and iodide ions oxidation. Herein, we report a novel approach for selectively stabilizing both organic amine salt and lead iodide (PbI2) precursor solutions in two‐step method. The introduction of benzene‐1,3‐dithiol into organic amine salt solution can mitigate amine‐cation side reactions due to the formation of an acidic and reducing environment. Simultaneously, decamethylferrocene (FcMe10/FcMe+10) pair can act as a redox shuttle in PbI2 solution to concurrently oxidize Pb0 and reduce I2 in cyclic manner. Consequently, the PVSCs device fabricated from ameliorative precursor solutions demonstrates superior power conversion efficiency of 25.31 %, retaining 95 % of its efficiency after 21 days of solution aging. Moreover, the unencapsulated devices maintain 85 % of primitive efficiency for 1500 h at maximum power point tracking under continuous illumination. This work establishes a fundamental guidance and scientific direction for the stabilization of two‐step perovskite precursor solutions.

Investigating the effect of finite ionic size and solvent polarization on induced charge electro-osmosis around a perfectly polarizable cylinder

Many industrially relevant microfluidic applications use concentrated solutions of macro-molecular solutes dissolved in polar solvents like water, which are typically deployed at high voltages. In this study, we investigate the effect of finite ionic sizes and solvent polarization on induced charge electro-osmotic flow around a perfectly polarizable cylinder, at high electric field strengths and ionic concentrations. The flow is actuated by means of a direct current electric field, and the step response of various flow parameters are studied numerically. Finite ionic sizes, defined through a steric factor ν, are modeled using the modified Poisson–Nernst–Planck model. Additionally, a field-dependent permittivity, characterized by a solvent polarization number A, accounts for molecular re-orientation effects. Our findings reveal an ion-size modulated decrement in charge concentration in the electrical double layer and an augmentation in the electric field. Remarkably, the resulting flow velocities increase with ion size. Solvent polarization, on the other hand, results in a marked reduction in flow velocities. Steric effects, however, dominate over a large range of parameter space (applied voltage and bulk ionic concentration) as compared to solvent polarization. Finally, we demonstrate that unequal ionic sizes result in flow asymmetries at the steady-state, thereby generating net electro-phoretic motion of suspended particles.

A cautionary tale of basic azo photoswitching in dichloromethane finally explained

Many studies of azobenzene photoswitches are carried out in polar aprotic solvents as a first principles characterization of thermal isomerization. Among the most convenient polar aprotic solvents are chlorinated hydrocarbons, such as DCM. However, studies of azobenzene thermal isomerization in such solvents have led to spurious, inconclusive, and irreproducible results, even when scrupulously cleaned and dried, a phenomenon not well understood. We present the results of a comprehensive investigation into the root cause of this problem. We explain how irradiation of an azopyridine photoswitch with UV in DCM acts not just as a trigger for photoisomerization, but protonation of the pyridine moiety through photodecomposition of the solvent. Protonation markedly accelerates the thermal isomerization rate, and DFT calculations demonstrate that the singlet-triplet rotation mechanism assumed for many azo photoswitches is surprisingly abolished. This study implies exploitative advantages of photolytically-generated protons and finally explains the warning against using chlorinated solvent with UV irradiation in isomerization experiments.

Fabrication and Efficient Interfacial Assembly of Bright Red-Emitting Carbon Quantum Dots for Security-Warning Textiles.

Carbon quantum dots (CQDs) have attracted more attentions due to their multiple performances. However, the fabrication of long-wavelength emitting CQDs with aliphatic precursors still remains a challenge, mainly because it is difficult to generate large sp2 domains to reduce energy gap, which is not conducive to a redshift of the luminescence peak. Hereon, by regulating the pH of citric acid and thiourea mixture, a N, S co-doped CQD emitting bright red fluorescence at 635nm is successfully fabricated through the solvothermal reaction under acidic condition, achieving a high quantum yield of 32.66%. Solvatochromic effects of the CQDs are discussed through theoretical equations and models, which confirm that the hydrogen-bonding interaction dominates the fluorescence emission behavior of CQDs in polar solvents. Besides, a feasible strategy is proposed to prepare an anti-counterfeiting textile via the deposition of red-emitting CQDs onto cotton fibers, through rapidly evaporating the preferred organic solvent. As expected, the CQD-decorated textiles exhibit encouraging anti-counterfeiting and security-warning functions, along with underwater and long-distance detectability, washability, and sun resistance. It is worth noting that the present work is innovative in realizing the application of red-light-emitting CQDs in the fields of security-warning textiles.

Disclosing the mechanism of uranium(VI) solvent extraction by polydentate ligands in a polar solvent: The role of ion pairs

Uranium is a key element in nuclear power. Developing new extraction systems for its purification and concentration is an important task for improving the nuclear fuel cycle. In this work solvent extraction and uranyl complexes with tri-dentate pyridine-based and tetra-dentate phenanthroline-based diphosphonates were studied in thorough detail, both in the organic phase and the solid state. A combination of experimental methods (loading isotherms and conductivity measurements), spectroscopic techniques (UV–vis, EXAFS, 31P NMR, and Raman spectroscopy) and theoretical calculations were used to disclose the mechanism of U(VI) solvent extraction. We demonstrated that with tetradentate phenanthroline-based ligands, tight ion pairs ([UO2LNO3]+[UO2(NO3)3]−) are formed. With tridentate ligands, U(VI) forms a mixture of complexes with different stoichiometries. Significant differences in the structure of complexes with tridentate ligands in the solid state compared to complexes in the organic solution were also shown.

CsPbBr3@PbSO4 nanocomposites with near-unity photoluminescence and ultrastability via in-water in situ embedding synthesis strategy

Perovskite quantum dots (PQDs) are emerging as promising nanomaterials for optoelectronic applications. However, developing a cost-effective green synthesis process that simultaneously possesses satisfactory photoluminescence quantum yield (PLQY) and stability remains a severe challenge. Here, CsPbBr3@PbSO4 nanocomposites with a near-unity PLQY of 99.8 % and robust ambient stability are synthesized in situ in water via 4-Bromobenzenesulfonic acid and ditetradecylamine ligands. Notably, these nanocomposites show no decline in PLQY even after being immersed in water for over 250 days, and also exhibit superior stability against heating, ultrasonication, UV irradiation, anion exchange, and erosion by polar solvents. First-principles calculations reveal that CsPbBr3@PbSO4 nanocomposites can form a natural quantum well structure, which effectively promotes the radiative recombination of carriers in CsPbBr3 QDs. Meanwhile, the remarkable stability is attributed to the ultrahigh decomposition enthalpy of PbSO4 that serves as a strong barrier preventing the invasion of anions and polar media into the embedded CsPbBr3 QDs. Finally, besides the convenient application of green fluorescent paper, a fingerprint recognition is demonstrated by fabricating a bright-green LED integrated with the CsPbBr3@PbSO4 nanocomposites powder and a commercial UV chip. This work provides a new strategy for green synthesis and practical application of high-efficient and ultrastable PQDs.

Inhibitory Potency of Active metabolites from Different Polarities of Datura Stramonium Seed extracts: GC-MS Analysis, Biological Evaluations, and Molecular Docking Studies

Datura Stramonium is a well-known and important medicinal plant that is widely used in various medical systems to treat conditions such as asthma, diabetes, and inflammatory diseases. The aim of this study was to prepare extracts of D. stramonium seeds in different solvent polarities for assessing phytochemical potential, in vitro biological activities, and molecular docking studies. Phytochemical screening was conducted to determine the phytochemical composition, while GC-MS analysis was used to identify secondary metabolites of D. Stramonium. The seed extracts were molecularly docked to evaluate bioactive and antioxidant activity. The minimum inhibitory concentration (MIC) of the extracts against bacteria such as S. aureus, E. coli, Bacillus subtilis, and Proteus mirabilis was determined. Antifungal activity was also tested against fungi including Aspergillus flavus, Fusarium oxysporum, Aspergillus niger, and Candida albicans. The results of phytochemical screening indicated that the primary plant constituents in all extracts of different polarities are alkaloids, flavonoids, tannins, mucilage, sterols, heterosides, triterpenoids, and cardiac glycosides. Most molecules in the hexane, ether, and chloroform extracts consist of fatty acids, sterols, glycosides, triterpenoids, alkaloids, and phenolic compounds, as revealed by GC-MS analysis. Conversely, extracts from polar solvents like methanol, ethanol, and water are abundant in alkaloids. In vitro antibacterial and antifungal activities demonstrated that ether, methanol, and ethanol extracts were more effective than inhibiting the four bacterial strains compared to the antibiotics Oxacillin and Cefuroxime. The ether and methanol extracts exhibited better zones of inhibition and significant MIC values against A. niger and C. albicans compared to the control and fluconazole. The free radical inhibition (DPPH) (24.92 ± 5.31 μg/mL) for the ethanol extract indicates Datura's antioxidant capacity. It is believed that the main phytochemicals are responsible for the enhanced antioxidant activity observed in other studies. The docking study revealed that the bioactive compounds linoleic acid and atropine formed better hydrogen bonding interactions with proteins than pi-alkyl and alkyl bonds.

Biochemical Screening, In-vitro and In-silico Characterization of Citrullus colocynthis Fruit Extracts: A Combined Experimental and Computation Study.

Several medicinal plants are identified as therapeutic agents for the world's most deadly disease cancer. A member of the "Cucurbitaceae" family of medicinal plants, Citrullus colocynthis (C. colocynthis) has various pharmacological actions. In the present study we have focused on the phytochemical analysis, antimicrobial, anticancer and in silico investigation of fruit extracts of C. colocynthis. The chloroform, pure ethanolic and aq. ethanolic extracts of C. colocynthis whole fruit, peel and pulp separately have been investigated. The phytochemical analysis revealed the presence of alkaloids, flavonoids, steroids, phenols, saponins and glycosides in various parts of the fruit. Some compounds have been identified using GC-MS analysis by comparing with NIST library data. The antimicrobial activity of all extracts was checked by agar well diffusion method against five different bacterial strains such as A. baumannii, K. pneumonia, S. aureus, P. aeruginosa and E. coli. The zone of inhibition (ZOI) ranged between 11 mm to 27 mm against different strains. The polar solvent extracts (ethanolic and aq. ethanolic extract) of peel showed good sensitivity against all bacterial strains as compared to non-polar solvent (chloroform extract), which showed activity only against Staphylococcus aureus and Pseudomonas aeruginosa. The cytotoxic activity of C. colocynthis all extracts against human brain cancer cell lines (U-87) was assessed using MTT assay. The % cell viability of ethanolic (ET-PL), and aq. ethanolic extract of whole fruit and pulp showed promising results. The cancerous cell line U-87 seems to be more sensitive towards polar solvents (ethanolic and aq. ethanolic) pulp extracts than peel. Further, based on invitro results, compounds identified in ET-PP were screened for their potential as antibacterial and anticancer agents through molecular docking and MMGBSA studies. These studies strongly supported the in-vitro study results and identified new drug candidates.

Use of green polar aprotic solvents TamiSolve® NxG, DMSO and methyl-THF for the synthesis of asymmetric polyimide-based biogas purification membranes

Valorization of biogas to biomethane through membrane-based purification of its multi-component stream primarily consisting of CH4 and CO2, holds significant potential as a crucial renewable energy source. Industrial membrane units classically comprise of membranes synthesized using non-solvent induced phase separation (NIPS), with polymer processing typically performed using conventional solvents, such as N-N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), etc. However, use and subsequent waste handling of these solvents present significant hazards, due to their toxicological nature, therefore calling for a shift to employ safer and ‘greener’ materials to facilitate sustainable production of these membranes. In current work, a novel and sustainable methodology for synthesis of CO2/CH4 gas separation flat-sheet asymmetric membranes was developed with commercially available Matrimid® 5218 polyimide, using TamiSolve® NxG, dimethylsulfoxide (DMSO) and 2-methyltetrahydrofuran (MeTHF) as green solvent medium. NIPS thermodynamic and kinetic aspects of the novel system were fundamentally analyzed through determination of ternary phase diagrams and viscosity profiles. Membranes were systematically tested for gas separation performance by varying Tamisolve-DMSO-MeTHF solvent ratios. Mixed gas CO2/CH4 separation factors in the range of 13 to 41, along with CO2 permeances upto 186 GPU were achieved. Furthermore, chemical crosslinking was applied in view of plasticization resistance of the membranes. Matrimid® membranes crosslinked with hyperbranched polyethylenimine (PEI) successfully displayed stability against CO2-induced plasticization upto CO2 feed partial pressures of 22 bar. The developed membrane synthesis method provides a sustainable framework for synthesizing polyimide-based membranes with tunable gas separation performances.

Physics-informed machine learning to predict solvatochromic parameters of designer solvents with case studies in CO2 and lignin dissolution

The polarity of solvents plays a critical role in various research applications, particularly in their solubilities. Polarity is conveniently characterized by the Kamlet-Taft parameters i.e., the hydrogen bonding acidity (α), basicity (β), and the polarizability (π*). Obtaining Kamlet-taft parameters is very important for solvents namely ionic liquids (ILs) and deep eutectic solvents (DESs). However, given the unlimited theoretical number of combinations of ionic pairs in ILs and hydrogen-bond donor/acceptor pairs in DESs, experimental determination of their Kamlet-Taft parameters is impractical. To address this, the present study developed two different machine learning (ML) algorithms to predict Kamlet-Taft parameters for designer solvents using quantum chemically derived input features. The ML models developed in the present study showed accurate predictions with high R2 and low RMSE values. Further, in the context of present interest in the circular bioeconomy, the relationship between the basicities and acidities of designer solvents and their ability to dissolve lignin and carbon dioxide (CO2) is discussed. Our method thus guides the design of effective solvents with optimal Kamlet-Taft parameter values dissolving and converting biomass and CO2 into valuable chemicals.

Interfacial Hydrogen-Bond Interactions Driven Assembly toward Polychromatic Copper Nanoclusters.

Constructing versatile metal nanoclusters (NCs) assemblies through noncovalent weak interactions between inter-ligands is a long-standing challenge in interfacial chemistry, while compelling interfacial hydrogen-bond-driven metal NCs assemblies remain unexplored so far. Here, the study reports an amination-ligand o-phenylenediamine-coordinated copper NCs (CuNCs), demonstrating the impact of interfacial hydrogen-bonds (IHBs) motifs on the luminescent behaviors of metal NCs as the alteration of protic solvent. Experimental results supported by theoretical calculation unveil that the flexibility of interfacial ligand and the distance of cuprophilic CuI···CuI interaction between intra-/inter-NCs can be tailored by manipulating the cooperation between the diverse IHBs motifs reconstruction, therewith the IHBs-modulated fundamental structure-property relationships are established. Importantly, by utilizing the IHBs-mediated optical polychromatism of aminated CuNCs, portable visualization of humidity sensing test-strips with fast response is successfully manufactured. This work not only provides further insights into exploring the interfacial chemistry of NCs based on inter-ligands hydrogen-bond interactions, but also offers a new opportunity to expand the practical application for optical sensing of metal NCs.

Solubility prediction and interaction mechanism of FOX-7 in ten solvents by molecular and thermodynamic modeling

Solubility is a fundamental physicochemical property of materials. Current solubility prediction models are often highly parameterized by existing data, leading to a serious issue of transferability; thus, it is still challenging to enhancing their accuracy and generalization-ability. In this study, we employ molecular dynamics (MD) simulations and some thermodynamic modeling methods (SMD, COSMO-RS, and COSMO-SAC) to predict the relative solubility of 1,1-diamino-2,2-dinitroethylene (FOX-7) in ten solvents. A meticulous comparison with experimental data reveals that the alchemical free energy approach based on MD simulations outperforms SMD, COSMO-RS and COSMO-SAC models in solubility prediction. Furthermore, we identify that the more negative solvation free energy corresponds to the higher solubility, and the stronger solute–solvent hydrogen bonding corresponds to the higher solubility for low polar solvents too. Finally, it is confirmed that the electrostatic attraction dominates the binding energy between solute and solvent molecules. This work transcends traditional solubility prediction by offering a robust theoretical framework and computational strategy, proving both economical and environmentally benign. It paves the way for the rational selection of solvents for FOX-7 crystallization and provides a versatile tool for predicting the solubility of organic compounds.

Highly Stable CsPbBr3@MoS2 Nanostructures: Synthesis and Optoelectronic Properties Toward Implementation into Solar Cells.

Halide perovskites (HPs) have gained significant interest in the scientific and technological sectors due to their unique optical, catalytic, and electrical characteristics. However, the HPs are prone to decomposition when exposed to air, oxygen, or heat. The instability of HP materials limits their commercialization, prompting significant efforts to address and overcome these limitations. Transition metal dichalcogenides, such as MoS2, are chemically stable and are suitable for electronic, optical, and catalytic applications. Moreover, it can be used as a protective media or shell for other nanoparticles. In this study, a novel CsPbBr3@MoS2 core-shell nanostructure (CS-NS) is successfully synthesized by enveloping CsPbBr3 within a MoS2 shell for the first time. Significant stability of CS-NSs dispersed in polar solvents for extended periods is also demonstrated. Remarkably, the hybrid CS-NS exhibits an absorption of MoS2 and quenching of the HP's photoluminescence, implying potential charge or energy transfer from HPs to MoS2. Using finite difference time domain simulations, it is found that the CS-NSs can be utilized to produce efficient solar cells. The addition of a MoS2 shell enhances the performance of CS-NS-based solar cells by 220% compared to their CsPbBr3 counterparts. The innovative CS-NS represents important progress in harnessing HPs for photovoltaic and optoelectronic applications.

Toward understanding the solid-liquid equilibrium behavior of dinotefuran by thermodynamic analysis and molecular dynamic simulation

Dinotefuran is a third-generation nicotinic insecticide with a wide insecticidal spectrum and low toxicity to humans and other mammals, which has a huge potential market. The insight into the solid–liquid equilibrium behavior of dinotefuran in various solvents could further guide the design, development, and refinement of the further crystallization process. However, the complexity and variability of the dissolution process make it very challenging to study. In this research, the solid–liquid equilibrium of dinotefuran in both mono-solvents and mixed solvents was systematically investigated through a combined approach of the experimentation and molecular dynamics simulation. Firstly, the solubility of dinotefuran in a range of solvents was ascertained using the laser dynamic monitoring method over spanning temperatures from 278.15 to 318.15 K. The results showed that the solubility of dinotefuran in mono-solvents increase with the temperature increasing, while the solubility in mixed solvents exhibited an initial increase followed by a decrease with the organic solvent molar fraction increasing. Then the experimental data were fitted using five thermodynamic models. The NRTL model has the lowest 102ARD and 104RMSD values, indicating the best correlation, validity and fit. The dissolution behavior of dinotefuran was explored by calculating the thermodynamic properties. The results indicated that dinotefuran dissolution was a spontaneous, disorder degree increase process, and dissolution an exothermic process except the isopropanol + water mixed solvents. Additionally, the influence of the physicochemical properties of the solvent on the dinotefuran dissolution process was investigated, with a particular focus on the critical role of solvent polarity. Hansen solubility and the preferred solvation parameters of dinotefuran in the solvents were also further calculated to analyze the dissolution process. For the studied mixed solvents, when the ratios of methanol, ethanol, isopropanol, and acetone reached 0.85, 0.75, 0.50, and 0.70, respectively, dinotefuran molecules turned to be preferentially solvated by the water molecules. Finally, molecular dynamics simulation was performed to reveal the mechanisms of dinotefuran dissolution, suggesting the greater solute–solvent interaction, the easier dissolution. The solid–liquid equilibrium data might provide a guidance for the development of environment-friendly and efficient formulation.

Proton Conduction via Water and Ammonia Coordinated Metal Cationic Species in MOF and MHOF Platforms.

Although metal-organic frameworks (MOFs) and metalo hydrogen-bonded organic frameworks (MHOFs) are designed as promising solid-state proton conductors by incorporating various protonic species intrinsically or extrinsically, design and development of such materials by employing the concept of proton conduction through coordinated polar protic solvent is largely unexplored. Herein, we have constructed two proton-conducting materials having different solvent coordinated metal cationic species: In-H2O-MOF, ({[In(H2O)6][In3(Pzdc)6] ⋅ 15H2O}n; H2Pzdc: pyrazine-2,3-dicarboxylic acid) with coordinated water molecules from hexaaquaindium cationic species, and MHOF-4, ([{Co(NH3)6}2(2,6-NDS)2(H2O)2]n; 2,6-H2NDS: 2,6-naphthalenedisulfonic acid) with coordinated ammonia from hexaammoniacobalt cationic species. Interestingly, higher proton conductivity was achieved for In-H2O-MOF (1.5×10-5 S cm-1) than MHOF-4 (6.3×10-6 S cm-1) under the extreme conditions (80 °C and 95 % RH), which could be attributed to enhanced acidity of coordinated water molecules having much lower pKa value than that of coordinated ammonia. Greater charge polarization on hydrogen atoms of In3+-coordinated water molecules than that of Co2+-coordinated ammonia led to the high conductivity of In-H2O-MOF, as evident by quantum chemical studies. Such a comparative study on metal-coordinated protic polar solvents in achieving proton conduction in crystalline solids is yet to be made.

High contrast stimuli-responsive fluorescence emitters based on carbazole-cyanostilbene derivatives with aggregation induced emission properties

Due to the aggregation induced emission (AIE) materials exhibiting obvious fluorescent emission changes under the external stimuli of heat, solvent, force and so on, significant efforts have been directed toward developing AIE-active materials with high contrast stimuli-responsive fluorescence behaviors. Herein, three electron-donor(D)-electron-acceptor(A) and D-A-D type organic fluorescence emitters of Cz-DC-tBu, Cz-DC-CN and Cz-DC-OMe were facilely synthesized using carbazole group as D unit and cyano group as A unit. They showed typical AIE features and exhibited remarkable color changes under mechanical force and in different polarity solvents, respectively. The stimuli-responsive mechanism of the compounds were investigated by powder X-ray Diffraction (PXRD) and density functional theory calculations (DFT), which revealed that the mechanofluorochromic behaviors were associated with the molecular packing modes, and the solvatochromic effects were caused by the intramolecular charge-transfer transition (ICT) effect. Significantly, it was found that Cz-DC-tBu showed high contrast stimuli-responsive behaviors through adjusting the substituent groups on the cyanostilbene unit with CN, OMe, and tBu groups, respectively. This study provided a new strategy for the design of AIE-active stimuli-responsive fluorescence emitters, and made them possible using in stress sensors, chemical detection, memory storage, anti-counterfeiting applications.

STUDY ON THE UV-VIS SPECTROSCOPIC PROPERTIES OF SUDAN III AND SUDAN IV DYES IN DIFFERENT ORGANIC SOLVENTS

Uv/vis spectroscopy is a simple, low cost technique that can be used to identify and quantify adultrants such as azo dyes in foods. In this study, the ultraviolet-visible absorption spectral properties of Sudan III and Sudan IV dyes in non-polar solvent hexane, moderately polar solvent acetonitrile, and highly polar solvent ethanol were investigated using UV-VIS spectrophotometry. The results showed that the absorption peaks of Sudan III dye in hexane, acetonitrile and ethanol were within wavelenth ranges of 254-362 nm, 264-364 nm and 258-348 nm respectively, while the absorption peaks of Sudan IV dye in hexane, acetonitrile and ethanol were within the wavelenth ranges of 256-345nm, 262-367nm and 275- 369nm respectively, with the dyes absorbing maximally within the ultra violent region of the electromagnetic spectrum. This study will be very useful to the food scientists as it will assist in determining the appropriate wavelength for measuring/quantifying sudan lll and sudan IV dyes in food as the trend of azo dye adulteration of food such as palm oil is now rampant and has become one of the major challenges of food safety.

Influence of Solvent Polarity on Crocin Content and Surface Properties of Saffron (Crocus sativus L.) Extracts.

The saffron composition is being widely studied for authenticity and traceability, but very few works have been carried out to investigate the relationship between the chemical and physico-chemical properties of saffron solutes and their technological functionality in colloidal systems. This study aims at evaluating the surface properties of saffron extracts obtained using solvents of different polarities to achieve extracts with different compositions in terms of the pattern and content of polar and medium polarity crocins. The air-water surface was evaluated alone and in the presence of Tween 20 at different surfactant-extract ratios. Saffron extracts were able to decrease the surface tension of the aqueous phase, indicating the presence of surface-active compounds. In the mixed saffron extract-Tween 20 systems, competitive adsorption at the air-water interface occurred when the surfactant was present at a low concentration, while at concentrations higher than the CMC, Tween 20 hindered the adsorption of the extract surface-active compounds. The results highlight the interesting technological functionality of saffron extracts for applications in colloidal systems. To better exploit their use in the design and development of formulated foods, nutraceutics and pharma products, further studies are needed to unravel the relationship between the composition of saffron extracts and corresponding surface activity.

Xylose Acetals - a New Class of Sustainable Solvents and Their Application in Enzymatic Polycondensation.

The use of organic solvents in academic research and industry applications is facing increasing regulatory pressure due to environmental and health concerns. Consequently, there is a growing demand for sustainable solvents, particularly in the enzymatic synthesis and processing of polyesters. Biocatalysts offer a sustainable method for producing these materials; however, achieving high molecular weights often necessitates use of solvents. In this work, we introduce a new class of alternative aprotic solvents with medium polarity produced directly from agricultural waste biomass in up to 83 mol% yield (on xylan basis). The new solvents have a largely unmodified xylose core and acetal functionality, yet they show no peroxide formation and provide reduced flammability risk. We also demonstrate their successful application in enzymatic polycondensation reactions with Candida antarctica lipase B (CaLB). In particular, the solvent dibutylxylose (DBX) outperformed the hazardous solvent diphenyl ether and facilitated polycondensation of the lignin-derived diester pyridine-2,4-dicarboxylate, yielding polyesters with a Mn of >15 kDa. Computational modelling studies provided further insight into the molecular structure and dynamics of CaLB in the presence of new solvents. Lastly, up to 98 wt% of the new xylose acetals were successfully recovered and recycled, further contributing to the sustainability of the overall process.