Fluorescence Emission Spectroscopy Research Articles

Mechanistic Insights into S-Depalmitolyse Activity of Cln5 Protein Linked to Neurodegeneration and Batten Disease: A QM/MM Study.

Ceroid lipofuscinosis neuronal protein 5 (Cln5) is encoded by the CLN5 gene. The genetic variants of this gene are associated with the CLN5 form of Batten disease. Recently, the first crystal structure of Cln5 was reported. Cln5 shows cysteine palmitoyl thioesterase S-depalmitoylation activity, which was explored via fluorescent emission spectroscopy utilizing the fluorescent probe DDP-5. In this work, the mechanism of the reaction between Cln5 and DDP-5 was studied computationally by applying a QM/MM methodology at the ωB97X-D/6-31G(d,p):AMBER level. The results of our study clearly demonstrate the critical role of the catalytic triad Cys280-His166-Glu183 in S-depalmitoylation activity. This is evidenced through a comparison of the pathways catalyzed by the Cys280-His166-Glu183 triad and those with only Cys280 involved. The computed reaction barriers are in agreement with the catalytic efficiency. The calculated Gibb's free-energy profile suggests that S-depalmitoylation is a rate-limiting step compared to the preceding S-palmitoylation, with barriers of 26.1 and 25.3 kcal/mol, respectively. The energetics were complemented by monitoring the fluctuations in the electron density distribution through NBO charges and bond strength alterations via local mode stretching force constants during the catalytic pathways. This comprehensive protocol led to a more holistic picture of the reaction mechanism at the atomic level. It forms the foundation for future studies on the effects of gene mutations on both the S-palmitoylation and S-depalmitoylation steps, providing valuable data for the further development of enzyme replacement therapy, which is currently the only FDA-approved therapy for childhood neurodegenerative diseases, including Batten disease.

Monitoring of cellulose-rich biowaste co-digestion with 3D fluorescence spectroscopy and mass spectrometry-based metabolomics

Anaerobic digestion (AD) is a promising waste management strategy that reduces landfilling while generating biogas. Anaerobic co-digestion involves mixing two or more substrates to enhance the nutrient balance required for microorganism growth and thus improve the degradation. Monitoring AD is crucial for comprehending the biological process, optimizing process stability, and achieving efficient biogas production. In this work, we have used three dimensional excitation emission fluorescence spectroscopy and mass spectrometry metabolomics, two complementary techniques, to monitor the anaerobic co-digestion (AcoD) of cellulose, ash wood or oak wood with food waste. The two approaches were compared together and to the biogas production records. Results of this experiment demonstrated the complementarity of both analytical techniques with the measurement of the biogas production since 3D fluorescence spectroscopy and MS metabolomics revealed the earlier molecular changes occurring in the bioreactors, mainly associated with the hydrolysis step, whereas the biogas production data reflected the biological activity in the last step of the digestion. Moreover, in all cases, the three data sets effectively delineated the differences among the substrates. While the two wood substrates were poorly degradable as they were richer in aromatic compounds, cellulose was highly degradable and was characterized by the production of several glycolipids. Then, the three tested AcoDs resulted in a similar 3D EEM fluorescence and metabolomics profiles, close to the one observed for the AD of food waste alone, indicating that the incorporation of the food waste drove the molecular degradation events in the AcoDs. Substrate-specific differences were appreciated from the biogas production data. The overall results of this research are expected to provide insight into the design of guidelines for monitoring AcoD.

Development and evaluation of anti-reflux functional-oral suspension raft composed of sodium alginate-mung bean protein complex

This study aimed to develop a sodium alginate (Na alginate) and mung bean protein (MBP) raft complex to improve gastric reflux symptoms. Na alginate and MBP complexes with different ratios (1:1, 2:1, and 3:1, respectively) were used for raft formulations through a wet Maillard reaction. Structural properties of raft strength, reflux resistance, intrinsic fluorescence emission spectroscopy, and Fourier transform infrared spectroscopy (FTIR) were investigated for rafts. The suspension 1:1 Na alginate/MBP with 0 h Maillard reaction time exhibited the lowest sedimentation volume among the suspensions. In contrast, 3:1 Na alginate/MBP with 6 h Maillard reaction time showed the highest sedimentation volume. Based on the results, the 3:1 Na alginate/MBP rafts had the best results, and the results were within acceptable limits. Functional properties, including antioxidant properties, the Helicobacter pylori inhibition assay, the pancreatic lipase inhibition assay, and angiotensin-converting enzyme (ACE) inhibition, were investigated for rafts. The Na alginate/MBP raft has similar characteristics to Gaviscon syrup and can be used for obesity, Helicobacter pylori infection, high blood pressure, and gastric reflux.

Wittig Synthesis, Optical Properties and Electrochemical Behaviors of Some Conjugated Derivatives of 4-Pyrones

The novel hetero-stilbene derivatives were synthesized by the Wittig reaction between 2-formyl-4-pyrones and polysubstituted imidazole-based phosphonium salts in the presence of a base. The optical properties of the products were investigated via UV–Vis absorption and fluorescent emission spectroscopy in dilute ethanol solution. Electrochemical properties were also studied by the cyclic voltammetry in CH2Cl2 solutions. The phosphorus ylides obtained from α-halocarbonyls were also condensed with 2-formyl-4-pyrone to give two electrochemically inactive and non-emitting products.

Novel strategy toward color-tunable and glow-in-the-dark colorless smart natural wooden window

Smart windows that use photochromic colorless wooden materials are an intriguing and urgent area of research. Herein, we create afterglow transparent woods with UV-induced photochromic capability. Infiltrating a lignin-modified wood (LMW) with a solution of methyl acrylate (MA) and rare-earth strontium aluminum oxide (SrAl2O4: Eu2+, Dy3+; SAOED) yielded afterglow and photochromic translucent wood. Preparing photoluminescent transparent wood effectively requires dispersing SAOED phosphor nanoparticles (NPs) in pre-polymerized MA without clumping. CIE (Commission Internationale de ĺEclairage) Lab colorimetric studies indicated that this transparent timber substrate changed color from colorless in daylight to greenish when exposed to ultraviolet rays. Micrographs taken using a transmission electron microscope (TEM) were analyzed to learn more about the morphology of the synthesized SAOED NPs. Different characterization techniques were applied on the photochromic translucent wood samples, including scanning electron microscopy (SEM), energy-dispersive X-ray analyzer (EDX), hardness properties, wavelength-dispersive X-ray fluorescent spectroscopy (WD-XRF), and absorption and emission spectroscopy. Absorption maximum wavelength was detected at 365 nm. Both 436 nm and 517 nm were observed as emission wavelengths in the developed photoluminescence wood. The results displayed that the manufactured transparent wood introduced superior protection from UV radiation and superhydrophobic activity. UV light triggered a rapid and reversible photochromic reaction in the transparent luminous wood.

New anthracene-based Oxime-Palladium complexes loaded on albumin nanoparticles, in vitro cytotoxicity, mathematical release mechanism studies and biological macromolecules interaction investigation

In this research work, two new palladium complexes [trans-Pd(C15H10NOCH3)2]Cl2 (1) and [cis- Pd(C15H10NOCH3)(PPh3)2Cl]Cl (2) were synthesized using an alkoxyme ligand named isophethalaldoxime. Then structure characterization has been done by FT-IR and different NMR (1H, 13C and 31P) spectroscopy. Then, their interactions with biological macromolecules including deoxyribonucleic acid and bovine serum albumin were studied using various spectroscopic methods such as UV–Vis absorption, fluorescence emission spectroscopy and circular dichroism. The results showed the binding of the prepared complexes to the deoxyribonucleic acid via grooves and different binding sites of bovine serum albumin. Fluorescence emission data showed that the mechanism of extinction of albumin emission by these compounds is static. Competitive titration was performed on albumin with eosin-Y, ibuprofen and digoxin as site markers I, II and III. The antitumor activity and toxicity of these compounds were evaluated on cancer cell lines A549 (leukemia) and K562 by in-vitro cytotoxicity test. The IC50 values showed the good activity of these complexes in inhibiting cancer cells. In the last section, the release mechanism of synthesized complexes from albumin nanoparticles (BNPs) was investigated and theoretical calculations were performed that showed Korsmeyer-Peppas mechanism for complex (1) and Quadratic mechanism for complex (2).

Photoluminescence Properties of Polythiophene/Tin Oxide (PTh/SnO2) Polymer Nanocomposites

In the present work, we have synthesized, polythiophene/tin oxide (PTh/SnO2) polymer nanocomposites through an in-situ chemical polymerization of thiophene monomers using anhydrous FeCl3 as an oxidant. The structural, thermal and optical characterization of PTh/SnO2 nanocomposites were investigated using X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analyzer and fluorescence emission spectroscopy. XRD spectra show the formation of pure polythiophene and incorporation of SnO2 nanofiller into the polythiophene matrix. FESEM images depict the formation of irregular rod and chain like structures with incorporation of SnO2 are noticed. TGA results reveal that the thermal stability of polymer nanocomposites is higher than that of pure polythiophene due to the strong interaction between nanofiller and polymer matrix. Fluorescence emission spectra show the emission intensity of polymer nanocomposites decreases as the concentration of SnO2 nanofiller increases due to the variation of rate of electron-hole recombination and conjugation length of polymer chain. Our results of fluorescence emission analyses suggest the PTh/SnO2 polymer nanocomposites could be a potential material for photonic devices.

Synthesis and characterization of hyperbranched conjugated polymers based on triphenylamine, phenoxazine, and benzothiadiazole for optoelectronic applications

In this work, two novel hyperbranched conjugated polymers poly(tris(4-(10-(2-ethylhexyl)-10H-phenoxazin-3-yl)phenyl)amine) (P1) and poly (tris(4-(7-(benzo[c][1,2,5]thiadiazol-4-yl)-10-(2-ethylhexyl)-10H-phenoxazin-3-yl)phenyl)amine) (P2) have been successfully synthesized via Direct polycondensation in the presence of Pd(OAc)2 as a catalyst. The chemical structures of novel conjugated polymers then were determined via Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR). Subsequently, the optical properties of conjugated polymers in different solvents were investigated via UV–Vis absorption and fluorescence emission (PL) spectroscopies, and were analyzed for optoelectronic applications.

Experimental and theoretical insights on the photophysical properties of ester-substituted indolizines

In this report, we present our latest results on the photophysical properties of substituted indolizines, which were previously obtained through the utilization of ultrasound (US) irradiation, in a one-pot and multicomponent strategy, allowing for a streamlined and straightforward preparation process. The photophysical properties of these derivatives were evaluated in solution using UV–Vis absorption and steady-state fluorescence emission spectroscopy. Our results reveal that these compounds exhibit absorption maxima in the UV-A-violet region. The electronic transitions could be related to spin and symmetry allowed ¹π→π* electronic transitions. The indolizines present fluorescence in the violet-to-green region. Both ground and excited states were shown to be tailored by the substituents in the indolizine core. In addition, the role of the solvent in the deactivation of the excited state proved to be critical in the successful exploration of these compounds as optical sensors for benzene. When benzene was added to the ethanolic solution, the indolizines usually exhibited fluorescence quenching, with a linear relationship between the amount of benzene and the emission intensity. Theoretical calculations were also employed to gain a deeper understanding of the solute-solvent interactions.

Black garlic particles as a natural pigment and emulsifier in a Pickering emulsion based low fat innovative mayonnaise: Improved rheology and bioactivity

Black garlic is rich in brown pigments and Maillard reaction products are known for antioxidant activity and health promoting effects. In the present investigation, we report a facile strategy for fabricating low-fat innovative mayonnaise (IM) using black garlic particles (BGP) as a natural pigment, and a functional ingredient. Whey protein concentrate and high methoxyl pectin at optimized concentrations were utilized for fabricating an IM which served as a control. IM5 and IM10 were ternary composites constituting whey protein, high methoxyl pectin along with BGP (@5 and 10% respectively). The formulation IM10 (BGP @10%) showed high firmness and low spreadability quotient, hence IM5 was taken forward for fabrication for two more variants namely IM-J (using low methoxyl pectin (LMP) from jackfruit peels) and IM-C (LMP from citrus). The effect of BGP and LMP on the functional quality of IM was confirmed through zeta potential, antioxidant activity, textural, rheological, and microscopic evaluation. Fluorescence microscopy confirmed the presence of solid particles over the fat phase of IM, while interaction of pectin and whey proteins was demonstrated through fluorescence emission spectroscopy which clearly displayed stabilization of IM through the formation of Pickering emulsion. Pronounced difference in color and flavor score with BGP established high sensory scores in IM5, IM-J, and IM-C. Rheology supported the stabilizing effects of LMP in IM-J and IM-C in terms of speedy recovery of thixotropy, with recovering storage modulus (G′). Enhanced viscosity of IM-C and IM-J further corroborated the dual effect of LMP and BGP in improving emulsifying and functional quality of IM. Enhanced oxidative stability of IM was established by reduced peroxide and Totox values. Overall our results suggest the promising applications of black garlic as functional ingredient in protein and pectin based Pickering emulsions.

Digestive enzyme corona formed in simulated gastrointestinal tract and its impact on EGCG release from banana resistant starch nanoparticles

The interaction of nanocarriers with gastrointestinal enzymes upon oral administration significantly impacts their performance as delivery systems. This work investigated the interaction between epigallocatechin gallate (EGCG) loaded into banana resistant starch nanoparticles (RSNPs) and digestive enzymes and its implications for EGCG release. The formation of a protein corona on EGCG-RSNPs in simulated gastrointestinal fluids was confirmed. The formation of this protein corona led to structural alterations in the pepsin and trypsin. Changes in enzyme conformation upon interaction with EGCG-RSNPs were elucidated using UV–Vis absorption and emission fluorescence spectroscopy. The activity of the enzymes remained largely unaffected despite these conformational changes. Additionally, the presence of the protein corona led to a slower, reduced release rate of EGCG. The results of this work will contribute to the growing knowledge of nanocarrier design for the delivery of bioactive compounds, paving the way for the development of innovative therapeutic strategies and functional foods with more excellent health benefits.

AIE‐Active ‘Turn‐On’ Sensors for Highly Selective Detection of Bovine Serum Albumin**

AbstractTetraphenylethylene (TPE)‐based, two molecular ‘Turn‐On’ probes i. e. 4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetraphenol (tetrahydroxy‐TPE, coded as: TPE‐1) 4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetraaniline and tetraamino‐TPE, coded as: TPE‐2) have been successfully reported for the selective detection of bovine serum albumin (BSA) over its other biological competitors. The BSA sensing has been investigated using UV‐Vis absorption and fluorescence emission spectroscopy, where the fluorescence of probes tetrahydroxy‐TPE and tetra‐amino‐TPE was significantly enhanced in the presence of BSA. The BSA sensing was also characterized by visual eye detection, where a significant color change of probe tetrahydroxy‐TPE and tetra‐amino‐TPE was observed with BSA. The detection limit for BSA was calculated to be 0.2 nM and 1.41 nM for using probes tetrahydroxy‐TPE and tetra‐amino‐TPE, respectively. The binding constant was observed to be1.8×103 M and 1.4×103 M for probes tetrahydroxy‐TPE and tetra‐amino‐TPE, respectively. A molecular docking study is also performed to investigate the detailed interactions between probes tetrahydroxy‐TPE and tetra‐amino‐TPE with BSA. The lowest binding energy conformation for probes tetrahydroxy‐TPE and tetra‐amino‐TPE was found at −8.1 kcal/mol and −8.2 kcal/mol, respectively.

Tandem High-Pressure Crystallography-Optical Spectroscopy Unpacks Noncovalent Interactions of Piezochromic Fluorescent Molecular Rotors.

To develop luminescent molecular materials with predictable and stimuli-responsive emission, it is necessary to correlate changes in their geometries, packing structures, and noncovalent interactions with the associated changes in their optical properties. Here, we demonstrate that high-pressure single-crystal X-ray diffraction can be combined with high-pressure UV-visible absorption and fluorescence emission spectroscopies to elucidate how subtle changes in structure influence optical outputs. A piezochromic aggregation-induced emitter, sym-heptaphenylcycloheptatriene (Ph7C7H), displays bathochromic shifts in its absorption and emission spectra at high pressure. Parallel X-ray measurements identify the pressure-induced changes in specific phenyl-phenyl interactions responsible for the piezochromism. Pairs of phenyl rings from neighboring molecules approach the geometry of a stable benzene dimer, while conformational changes alter intramolecular phenyl-phenyl interactions correlated with a relaxed excited state. This tandem crystallographic and spectroscopic analysis provides insights into how subtle structural changes relate to the photophysical properties of Ph7C7H and could be applied to a library of similar compounds to provide general structure-property relationships in fluorescent organic molecules with rotor-like geometries.

Synthesis, characterization and biological evaluation of three novel copper(II) clonixinate complexes with methylpyridines: Insights into structure, DNA and BSA binding properties and anticancer activity

Three novel mononuclear copper(II) complexes 1–3 with clonixinate anion (clon) derived from clonixin (Hclon) and α-, β-, or γ-methylpyridine (α-, β-, or γ-pic) were synthesised. The compounds were characterised by IR, UV–Vis and EPR spectroscopy and elemental analysis. The redox properties of the prepared complexes were studied by square wave voltammetry. The structure of the complexes [Cu(clon)2(α-pic)2] (1), [Cu(clon)2(β-pic)2] (2), [Cu(clon)2(γ-pic)2] (3) was determined by single-crystal X-ray analysis and the intermolecular interactions were studied by Hirshfeld surface analysis. The interaction of the studied complexes with calf thymus DNA was investigated by UV–Vis absorption titration and further investigation of the possible intercalative mechanism of action was carried out by fluorescence quenching studies with ethidium bromide-DNA adduct monitored via fluorescence emission spectroscopy. Interactions with bovine serum albumin were also evaluated by fluorescence emission spectroscopy. The cytotoxicity and selectivity of 1–3 were studied in vitro on a human breast cancer cell line (MCF-7), a lung cancer cell line (A549), a human glioblastoma cell line (U-118MG) and healthy human fetal lung fibroblast cells (MRC-5). All three complexes showed low to moderate ability to interact with calf thymus DNA, probably through partial intercalation, high and reversible binding to serum albumin and promising cytotoxic effects on the MCF-7 cancer cell line with reasonable selectivity for complexes 1 and 2. Finally, the mitochondrial respiratory capacity of MCF-7 tumour cells was also studied and showed a reduced activity after the addition of the studied complexes.

Insights into the binding of half-sandwich phosphino Ir(III) and Ru(II) complexes to deoxyribonucleic acid, albumin and apo-transferrin: Experimental and theoretical investigation

A group of cytotoxic half-sandwich iridium(III) (Ir(η5-Cp*)Cl2PPh2CH2OH (IrPOH)), (Ir(η5-Cp*)Cl2P(p-OCH3Ph)2CH2OH (IrMPOH)), and ruthenium(II) (Ru(η6-p-cymene)Cl2PPh2CH2OH (RuPOH), Ru(η6-p-cymene)Cl2P(p-OCH3Ph)2CH2OH (RuMPOH)) complexes with phosphine ligands exhibit the ability to (i) slow hydrolysis which is reversed by adding a high NaCl concentration; (ii) oxidation of NADH to NAD+; (iii) induction of cytotoxicity towards various cancer cell lines. Furthermore, we found that RuPOH and RuMPOH selectively inhibit the proliferation of skin cancer cells (WM266-4) while Ir(III) complexes were found to be moderate against prostate cancer cells (DU-145). Herein, to elucidate the cytotoxic effects, we investigated the interaction of these complexes with DNA and serum proteins by gel electrophoresis, fluorescence spectroscopy, and molecular docking studies. Fluorescence spectroscopic data (calf thymus DNA: CT-DNA titration), together with analysis of DNA fragmentation (gel electrophoresis) and molecular docking provided evidence for the multimodal interaction of Ir(III) and Ru(III) complexes with DNA with predominance of intercalation and minor groove binding. All examined complexes caused single-stranded cleavage of the sugar–phosphate backbone of plasmid DNA. The affinity of the complexes for apo-transferrin (apo-Tf) and human serum albumin (HSA) was evaluated by fluorescence emission spectroscopy to calculate the binding constants which suggested a tight and reversible binding. Moreover, ruthenium complexes can mimic the binding of iron compounds to specific biomolecules such as albumin and transferrin better than iridium complexes. In silico study indicate that complexes mostly bind to (i) apo-Tf with a preference for a single binding site and/or (ii) to dock within all the four predicted binding sites of HSA with the predominance of site I which include tryptophan residues of HSA. This class of ruthenium(II) and iridium(III) complexes has unusual features worthy of further exploration in the design of novel anticancer drugs.

Insights into the electronic properties of 6-substituted quinolone derivatives: A solvatochromic study

Solvent dependent photophysical properties of 6 -substituted N-methyl quinolone molecules namely 6-amino-1-methylquinolin-2(1H)-one (AMQ), 1-methyl-6-(methylamino)quinolin-2(1H)-one (MAMQ), 1-methyl-6-nitroquinolin-2(1H)-one (NMQ) have been studied using steady state UV–Visible absorption, fluorescence emission spectroscopy, fluorescence lifetime measurements and quantum mechanical calculations. It was found that amine and methylamine substitution at 6-position of quinolone moiety enhanced the fluorescent property whereas nitro substitution rendered it non-fluorescent in all the experimental solvent systems. Maximum redshifted spectra were found in dimethyl sulfoxide (DMSO) compared to both alcoholic solvents and pure water. Significant charge transfer in HOMO to LUMO transition was revealed by quantum mechanical calculations but the direction was different depending on the nature of substitution. The pH response of the molecules were also investigated in pure water and the pKa values were found to be 3.70 and 3.90 for AMQ and MAMQ respectively. Analysis of radiative and non-radiative rate constants in all the solvents showed that the deactivation process may be different depending on hydrogen bond donation ability of the solvent. The spectral shift was rationalised by grouping the solvents based on their hydrogen bonding ability.

Thiazolidine-Based Fluorescent Chiral Ionic Liquids for Trace Copper(II) Ion Sensing

This study presents a comprehensive analysis of the synthesis and photophysical properties of thiazolidine-functionalized chiral ionic liquids (CILs) derived from L-cysteine. The synthesis involves a four-step route, encompassing N-protection, coupling reactions with bromoalcohols, and ionic liquid formation. The optical properties of the compounds were evaluated using UV–Vis absorption and fluorescence emission spectroscopies, revealing distinct behavior for different heterocycles and counter-ions. Notably, the investigation reveals that thiazolidine-based CILs exhibit unconventional intrinsic luminescence characteristics. Building upon these photophysical properties, an interaction study was conducted between copper (II) and the CILs. The findings exhibit a robust linear relationship between the optical response and the concentration of the metal ion. Through the calculation of the Stern–Volmer quenching constant, it was determined that the 1:1 binding model is applicable. This research underscores the potential of UV–Vis absorption spectroscopy as a highly sensitive method for detecting metal ions. By elucidating the synthesis, photophysical behavior, and metal ion interaction of thiazolidine-based CILs, this study contributes valuable insights into the field of functionalized ionic liquids and their potential applications in various areas.

Coumarin-based thiosemicarbazones as colorimetric and fluorescent “Turn on” chemosensors for fluoride ions and their applications in logic circuits

Herein, we have reported two novel coumarin based thiosemicarbazones as anionic sensors. The structural elucidation of the synthesized sensors is done by 1HNMR, 13CNMR, CHN analysis, UV–Visible spectroscopy, and fluorescence emission spectroscopy. These sensors displayed naked eye view as color change from colorless to yellow. The chemosensing behavior is attributed to the presence of acidic proton which was abstracted by F¯ ions triggering spectral changes. Methanol, water, HCl, and trifluoroacetic acid were used to reverse the reaction of F¯ ions. The limit of detection (LOD) for F− ions was determined as 23.33 and 16.90 μM while the binding constant was assessed as 4.92 × 104 and 4.84 × 104 M−1 for sensor based on UV–Vis titration using Benesi-Hildebrand equation. These sensors can be used in daily life applications (test strip and detection of F¯ ions in toothpaste sample).

Simplified silicon recovery from photovoltaic waste enables high performance, sustainable lithium-ion batteries

Conventional recycling methods to separate pure silicon from photovoltaic cells rely on complete dissolution of metals like silver and aluminium and the recovery of insoluble silicon by employing multiple leaching reagents. A common approach that eschews hydrofluoric acid (HF) treatment is the double reagent approach which utilizes nitric acid (HNO3) and potassium hydroxide (KOH) to separate the metals from silicon cell. However, the double reagent approach is unable to remove the anti-reflective coating and use of KOH leads to formation of insoluble precipitates, in turn affecting the purity of recovered silicon. Herein, we report a single reagent approach for a streamlined process for recovery of high purity silicon with unmatched recovery yield. Phosphoric acid, (H3PO4) identified as a reagent for this approach, directly targets the anti-reflective coating and separates the Ag and Al present on the Si wafer surfaces. This approach led to an impressive recovery rate of 98.9% with a high purity of 99.2%, as determined by X-ray fluorescence and Inductively-coupled plasma optical emission spectroscopy. Such high-purity of recovered silicon enables upcycling into anodes for lithium-ion battery, with the battery performance comparable to as-purchased silicon. Such recovered silicon lithium-ion battery anodes demonstrated a high specific capacity of 1086.6 mAh g−1 (62.3% of its initial specific capacity), even after 500 cycles at a high charging rate of 1.0C while maintaining high coulombic efficiency (>99%).

Effects of Enol-imine/Keto-amine tautomerism and conformational changes on the electronic spectra of a novel 1,2,4-triazole ortho-hydroxyaryl Schiff base in different solvents

In this study, a novel o-hydroxyaryl Schiff base bearing the 1,2,4-triazole heterocyclic core, (E)-2-(((4H-1,2,4-triazol-4-yl)imino)methyl)-6-methoxyphenol, was synthesized and structurally characterized by NMR (1H- and 13C-) and IR spectroscopies as well as by Density Functional Theory (DFT) electronic structure calculations. The compound was then investigated by UV–Vis absorbance and fluorescence emission spectroscopies in different solvents. The wavelength shifts observed in the band corresponding to the lowest energy transition in the absorbance spectra upon changing the solvent, as well as in the emission bands observed in the fluorescence spectra (upon excitation at 310 nm) were explained considering the effects of solvent-induced conformational changes and photoinduced enol-imine/keto-amine tautomerism. The interpretation of the experimental results was supported by structural data calculated for the different isomeric forms of the compound and of their electronic spectra in the gas phase and in solvents of different polarity. Solvent effects were also evaluated at the light of the Kamlet-Taft and Catalán solvatochromic models.