Involving Charge Transfer Research Articles

N-Aromatic Complexation in Tetraphenyl Porphyrin Iron (III)-Pyridine: Evidence of Spin-Flip via Gas-Phase Electronic Spectroscopy.

There is growing interest in the electronic properties of metalloporphyrins especially in relation to their interactions with other molecular species in their local environment. Here, UV-VIS laser photodissociation spectroscopy in vacuo has been applied to an iron-centred metalloporphyrin (FeTPP+) and its N-aromatic adduct with pyridine (py) to determine the electronic effect of complexation. Both the metalloporphyrin (FeTPP+) and pyridine adduct (FeTPP+⋅py) absorb strongly across the spectral region studied (652-302 nm: 1.91-4.10 eV). Notably, a large blue shift was observed for the dominant Soret band (41 nm) upon complexation (0.47 ± 0.02 eV), indicative of strong pyridine binding. Significant differences in the profiles (i.e. number and position of bands) of the electronic spectra are evident comparing FeTPP+ and FeTPP+⋅py. Time-dependent density functional theory calculations were used to assign the spectra, revealing that the FeIII spin-state flips from S = 3/2 to S = 5/2 upon complexation with pyridine. For FeTPP+, all bright spectral transitions are found to be π-π* in character, with electron density variously distributed across the porphyrin and/or its phenyl substituents. Similar electronic excitations are observed for FeTPP+⋅py, with an additional bright transition which involves charge transfer from the porphyrin to the pyridine moiety.

Supercapacitor properties of partially oxidised-MXene quantum dots/graphene hybrids: Fabrication of flexible/wearable micro-supercapacitor devices

Recently, combining the synergistic properties of two-dimensional (2D) and zero-dimensional (0D) materials has attracted significant attention for energy applications. Here, we report the synthesis and characterization of partially oxidised-MXene quantum dots (PO-MXQDs) and reduced graphene oxide composite (PO-MXQDs/rGO) and investigate the resulting composites for energy storage applications towards supercapacitors. Density functional theory (DFT) simulations are used to examine the electrical and structural features of PO-MXQDs/rGO by predicting the chemical interaction involving charge transfer from PO-MXQDs to rGO. The multilayer Artificial Neural Network (ANN) model with hyperparameter tuning was developed at different input parameters to optimize material compositions, concentrations, and types of electrolytes to obtain the suitable conditions for best supercapacitive performance. The optimized PO-MXQDs/rGO showed a specific capacitance value of 1137.8 F.g−1 and was utilized for the fabrication of flexible micro-supercapacitors (FMSCs) device through the mask-assisted vacuum filtration process and asymmetric coin-cell type supercapacitor devices (ACCDs). The FMSCs deliver a higher areal capacitance (5.26 mF.cm−2), high areal energy density (0.46 μWh.cm−2), high areal power density (210.48 μW.cm−2), and the FMSC device has ultra-high cyclic stability up to 30000 cyclic voltammetry (CV) cycles. This method provides an in-depth study on developing 0D-2D hybrid materials with the wisdom of machine learning (ML) and DFT toward energy storage applications.

Reticular Ratchets for Directing Electrochemiluminescence.

Electrochemiluminescence (ECL) involves charge transfer between electrochemical redox intermediates to produce an excited state for light emission. Ensuring precise control of charge transfer is essential for decoding ECL fundamentals, yet guidelines on how to achieve this for conventional emitters remain unexplored. Molecular ratchets offer a potential solution, as they enable the directional transfer of energy or chemicals while impeding the reverse movement. Herein, we designed 10 pairs of imine-based covalent organic frameworks as reticular ratchets to delicately manipulate the intrareticular charge transfer for directing ECL transduction from electric and chemical energies. Aligning the donor and acceptor (D-A) directions with the imine dipole effectively facilitates charge migration, whereas reversing the D-A direction impedes it. Notably, the ratchet effect of charge transfer directionality intensified with increasing D-A contrast, resulting in a remarkable 680-fold improvement in the ECL efficiency. Furthermore, dipole-controlled exciton binding energy, electron/hole decay kinetics, and femtosecond transient absorption spectra identified the electron transfer tendency from the N-end toward the C-end of reticular ratchets during ECL transduction. An exponential correlation between the ECL efficiency and the dipole difference was discovered. Our work provides a general approach to manipulate charge transfer and design next-generation electrochemical devices.

Intramolecular singlet fission: Quantum dynamical simulations including the effect of the laser field.

In the previous work [Reddy et al., J. Chem. Phys. 151, 044307 (2019)], we have analyzed the dynamics of the intramolecular singlet fission process in a series of prototypical pentacene-based dimers, where the pentacene monomers are covalently bonded to a phenylene linker in ortho, meta, and para positions. The results obtained were qualitatively consistent with the experimental data available, showing an ultrafast population of the multiexcitonic state that mainly takes place via a mediated (superexchange-like) mechanism involving charge transfer and doubly excited states. Our results also highlighted the instrumental role of molecular vibrations in the process as a sizable population of the multiexcitonic state could only be obtained through vibronic coupling. Here, we extend these studies and investigate the effect of the laser field on the dynamics of intramolecular singlet fission by explicitly including the coupling to the laser field in our model. In this manner, and by selectively tuning the laser field to the different low-lying absorption bands of the systems investigated, we analyze the wavelength dependence of the intramolecular singlet fission process. In addition, we have also analyzed how the nature of the initially photoexcited electronic state (either localized or delocalized) affects its dynamics. Altogether, our results provide new insights into the design of intramolecular singlet fission-active molecules.

Unravelling adsorption potential of expired clindamycin as corrosion inhibitor at mild Steel/HCl interface via response surface methodology, artificial neural network, electrochemical, and computational strategies

Corrosion has produced unprecedented disintegration of metals, constituting an imminent danger to mankind and triggering catastrophic global economic losses. The effectiveness of expired clindamycin (ECLI) as a low-cost corrosion control agent for mild steel was investigated utilising response surface methodology (RSM), artificial neural network (ANN), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), quantum chemical computation (QCC), and molecular dynamic simulation (MDS) studies in conjunction with thermometric and gasometric protocols at different HCl concentrations. The RSM model demonstrated an outstanding level of accuracy in predicting the mild steel corrosion inhibition efficiency (IE), the volume of hydrogen gas (VHG), reaction number (RN), and corrosion rate (CR). The model was significantly influenced by the operational parameters that were investigated, such as temperature (299–333 K), ECLI concentrations (100–500 mg/L), immersion time (1–6 h), and acid concentration (0.5–2.5 M). It was observed that as ECLI concentration increases, the VHG, RN, and CR decreased per time as well as % IE increased. The thermometric, gasometric, PDP, and EIS results showed percentage inhibition efficiency of 69.10, 69.49, 83.17, and 77.87 %, respectively. PDP revealed that ECLI operates as a mixed type of inhibitor, and EIS indicated that the inhibition process involves charge transfer. The Langmuir isotherm suits better and accurately describes the ECLI adsorption process on mild steel. The electron transfer propensity of the ECLI on the metal surface is measured by QCC using the DFT approach. MDS was implemented to establish the optimal adsorption orientation between ECLI and Fe (110). The inspection of surface morphology by SEM displayed the formation of a blanket-like layer on the steel by ECLI. To validate the experimental results, RSM and ANN prediction models were utilised, which were evaluated using a normal plot of residual, predicted versus actual, and residual versus run, and were found to be effective modelling tools. This study illustrates that ECLI can be utilised as a potent and affordable mild steel inhibitor, even at high acid concentrations.

Configuration-mediated excited-state energy dissipation in metal-bridged dimeric D-A fluorophores for enhanced photothermal therapy

Photothermal agents (PTAs) based on donor (D)-acceptor (A) NIR fluorophores show great promise in photothermal therapy due to their accessible molecular engineering to mediate excitation energy for high photothermal conversion. Except for molecular structural modification of D-A fluorophores, intermolecular arrangement in space greatly influences their excitation energy dissipation as well. But how to mediate their intermolecular arrangement is still challenging. Here we control the intermolecular orientation of chromophores via metal coordination to form Pt-bridged dimeric D-A fluorophores with different geometries. The formed configuration isomers show different intermolecular exciton coupling behaviors involving charge transfer (CT) evolution and internally limited molecular rotation, which greatly affect excited-energy dissipation. Compared with folded configuration with intense NIR emission (quantum yields (QYs) = 15.62 %), linear configuration favors non-radiative decays with low QYs (6.99 %) but enhanced photothermal conversion efficiency (PCE = 41.57 %). The self-assembled nanoparticles combining Pt-bridged dimeric D-A fluorophores with DSPE-PEG2000-RGD reveal superior photothermal therapeutic features with desirable biosafety. This research provides a new designing concept to mediate excited-state energy dissipation pathways at a sub-nano level for enhanced photothermal conversion. Statement of significanceD-A fluorophores as photothermal agents attract great attention in photothermal therapy due to their accessible molecular engineering. Besides molecular engineering of D-A fluorophores, the intermolecular packing manner is proven to greatly affect their excitation energy dissipation. But how to control intermolecular arrangement is still challenging. Here we control the intermolecular orientation of chromophores via metal coordination to form Pt-bridged dimeric D-A fluorophores with different geometries. Compared to the folded configuration, linear configuration facilitates charge transfer (CT) evolution and molecular rotation, which promotes non-radiative decays of excited energy for enhanced photothermal therapy.

Five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine

Three novel five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine were synthesized. Complexes differ by dioxolene ligands: 3,6-di-tert-butylcyclohexa-3,5-diene-1,2-dione (complex 1), 5,8-di-tert-butyl-2,3-dihydro-1,4-ethanoquinoxaline-6,7-dione (complex 2), 3,6-di-tert-butyl-4-methoxycyclohexa-3,5-diene-1,2-dione (complex 3). The geometry of the inner coordination core of all compounds is close to square pyramidal. The base of the pyramid is formed by oxygen atoms of the dioxolene ligands whereas phosphine occupies the apical position. The planes of dioxolenes are slightly bent relative to each other. The magnetic moment values at low temperatures correspond to one unpaired electron per molecule for all complexes. In the complex containing a methoxy group in the dioxolene ligand (3), an increase in the magnetic moment is observed upon heating above 250 K, which indicates the appearance of a fraction of molecules with a higher spin multiplicity. A slight elongation of the Co-O, Co-P distances and shortening of the CO bonds is observed at 353 K. DFT calculations using the TPSSh functional correctly reproduce geometries of the complexes as well as their electronic absorption and vibrational spectra. DFT predicts the doublet-state complexes to possess the lowest enthalpies. Gibbs free energy of sextet complex 3 in solution is lower than that of its doublet state. This agrees well with the experimental electronic absorption spectra. On the basis of TD DFT calculations, a strong NIR absorption band in the spectra of low-spin 1 and 2 is assigned to the transition involving charge transfer from cobalt to the dioxolene and PPh3 ligands (MLCT). The doublet molecules can be described by the (↑SQ—)(Co3+)(Cat2—) ↔ (Cat2—)(Co3+)(↑SQ—) resonance structures. The sextet state in all three systems represents the (↑SQ—)(↑↑↑Co2+)(PPh3)(↑SQ—) bis-semiquinonate complex of high-spin Co(II). On the basis of the conventional description the doublet → sextet transition in complexes can be interpreted as a VT/SCO transformation. The electron density analysis of the doublet → sextet transition in the 1 and 3 molecules reveals areas of both increase and decrease in the charge density near the Co and O atoms.

Computational investigation on the molecular driving forces for extraction of Co2+, Ni2+, and Fe3+ in poly(ethylene oxide)/thiocyanate salt aqueous two-phase systems

Aqueous two-phase systems are environmentally friendlier alternatives for hydrometallurgical processing and purification of metals. However, the viability of application of those systems in such processes is still under investigation, in which the comprehension of the fundamental aspects that govern the metal extraction is essential and can be further constructed using computational approaches. This research paper presents a comprehensive computational study on the fundamental nature of metal extraction in polymer-salt aqueous two-phase systems (ATPS), comparing the results of modeling and simulation work to the theoretical and experimental data available in the literature. Specifically, the mechanisms underlying the extraction of Co2+, Ni2+, and Fe3+, in ATPS formed by poly(ethylene oxide) (PEO) and thiocyanate salt are investigated, using quantum chemical calculations and molecular dynamics simulations. The formation of pseudo-polycations (PPCs) and thiocyanate metalates (complexes formed by a metal cation bonded to one or more anions) and the interaction of PEO fragments, thiocyanate, and aquo ligands with metal cations are explored. The binding affinity of these species is evaluated from various perspectives, including structural, electronic, and thermodynamic considerations. The solvation behavior of the species in solvents with different polarities is also examined. The findings elucidate the mechanisms governing metal cations partitioning behavior in PEO/thiocyanate ATPS, confirming the mechanisms proposed previously in the literature, involving charge transfer between metal-thiocyanate complexes and polyethylene oxide ether groups as well as interactions between metalate and PPCs. This study represents the first-ever computational investigation into the molecular driving forces behind metal extraction in polymer-salt ATPS, providing valuable insights for optimizing extraction processes and paving the way for future research in this field.

A porphyrin-based metal-organic framework Al-TCPP for highly selective sensing of copper ions with exceptional low limit of detection

Sensitive and selective detection of copper ions (Cu2+) using fluorometric methods is of growing significance due to their widespread industrial use, which poses severe environmental and health risks. Here, we reported a porphyrin-based luminescent metal-organic framework (labelling LMOF), Al-TCPP, which exhibits dual emission peaks at 467 and 646 nm upon excitation by a single wavelength. When exposed to Cu2+ ions, the fluorescence peak at 646 nm reduces while the intensity of the 467 nm remains steady. This intriguing property enables the construction of a ratio-metric fluorescence sensor that utilizes an internal standard, significantly enhancing Cu2+ sensing accuracy. Our study establishes a linear relationship (y = 0.0454x + 0.3081) between the fluorescence intensity ratio I467/I646 and the Cu2+ concentration, with a high correlation coefficient R2 = 0.9943. Impressively, the present Al-TCPP achieves a low limit of detection (LOD) of 5.28 nM, one of the lowest reported values for Cu2+ detection. The mechanism underlying this phenomenon involves charge transfer from TCPP ligands in Al-TCPP to Cu2+ ions, as revealed by solid-state NMR and X-ray photoelectron spectroscopy analysis. Utilizing Al-TCPP, we successfully developed test strips for the practical Cu2+ detection. Furthermore, the present Al-TCPP has also effectively applied to determine low Cu2+ content in various samples, including water, tea and serum. This study demonstrates the versatility and practical applicability of present Al-TCPP LMOF for selective detection of Cu2+ ions in diverse environments.

Unraveling the anti-corrosion mechanisms of a novel hydrazone derivative on steel in contaminated concrete pore solutions: An integrated study

IntroductionCorrosion-induced deterioration of infrastructure is a growing global concern. The development and application of corrosion inhibitors are one of the most effective approaches to protect steel rebar from corrosion. Hence, this study focuses on a novel hydrazone derivative, (E)-N′-(4-(dimethylamino)benzylidene)-2-(5-methoxy-2-methyl-1H-indol-3-yl)aceto-hydrazide (HIND), and its potential application to mitigate corrosion in steel rebar exposed to chloride-contaminated concrete pore solutions (ClSCPS). ObjectivesThe research aims to evaluate the anti-corrosion capabilities of HIND on steel rebar within a simulated corrosive environment, focusing on the mechanisms of its inhibitory effect. MethodsThe corrosion of steel rebar exposed to the ClSCPS was studied through weight loss and electrochemical methods. The surface morphology of steel rebar surface was characterized by FE-SEM-EDS, AFM; oxidation states of the steel rebar and crystal structures were examined using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) methods. Further, experimental findings were complemented by theoretical studies using self-consistent-charge density-functional tight-binding (SCC-DFTB) simulations. The performance of HIND was monitored at an optimal concentration over a period of 30 days. ResultsThe results indicated a significant reduction in steel rebar corrosion upon introducing HIND. The inhibitor molecules adhered to the steel surface, preventing further deterioration and achieving an inhibition efficiency of 88.4% at 0.5 mmol/L concentration. The surface morphology analysis confirmed the positive effect of HIND on the rebar surface, showing a decrease in the surface roughness of the steel rebar from 183.5 in uninhibited to 50 nm in inhibited solutions. Furthermore, SCC-DFTB simulations revealed the presence of coordination between iron atoms and HIND active sites. ConclusionThe findings demonstrate the potential of HIND as an effective anti-corrosion agent in chloride-contaminated environments. Its primary adsorption mechanism involves charge transfer from the inhibitor molecules to iron atoms. Therefore, applying HIND could be an effective strategy to address corrosion-related challenges in reinforced infrastructure.

Enhanced NIR fluorescence quantum yield of graphene quantum dots using dopants

In the present work, several efforts have been made theoretically to achieve an excellent non-toxic fluorescent graphene quantum dot (GQD) in the near-infrared region for the application of bio-imaging and sensing. Although the QY of GQDs is a maximum of 98.5% in the visible region, it is still very low, and it is as low as 7% in NIR. Sulfur and its group elements have been used for doping because they are pretty cheap and nontoxic and hence suitable for this application. The surface-doped position is considered for studying their effect on the energy band gap, absorption and fluorescence properties. The HOMO and LUMO isosurfaces have been analyzed in order to comprehend the nature of the dominant transition taking place in absorption spectra. Additionally, the quantitative indices, transition density matrix contour maps, and charge difference density have all been examined in order to determine whether this particular transition is locally excited or involves charge transfer. Following this, the QY of each GQD has been determined by considering the fluorescence spectra. The wavelength of fluorescence of doped GQDs is found to be in the region of 800–1400 nm, i.e. in NIR, which is strongly desirable for bio-imaging and bio-sensing applications. With a fluorescence of ∼850 nm, sulfur-doped GQDs (S-GQD: C52S2H18) have the greatest QY, 26%, which is larger than the 7% achieved earlier in NIR and such a high QY in NIR is being reported for the first time.

Experimental and theoretical insights into colossal supercapacitive performance of graphene quantum dots incorporated Ni3S2/CoS2/MoS2 electrode

Transition metal sulfides (TMS) are promising electrode materials for supercapacitor applications due to their unmatchable advantages. To overcome the deficiency of individual metal sulfides, the combination of one or more pseudocapacitive transition metals with conductive carbon material can be a plausible solution. In this work, a simple and one-step hydrothermal synthesis method is used to fabricate the flower-like Ni3S2/CoS2/MoS2 (NCMS) and Ni3S2/CoS2/MoS2-GQDs (NCMS-G) directly on Ni foam and used it as a binder-free electrode for high-performance supercapacitor applications. The NCMS-G-2.5 electrode possessed colossal specific capacitance (2364 Fg−1 at the current density of 2 Ag−1), excellent rate capability (55 % at the current density of 10 Ag−1), as well as good cycling stability (93 % retention after 10,000 cycles at the current density of 20 Ag−1). Furthermore, assembled NCMS-G-2.5//rGO asymmetric supercapacitor (ASC) device delivered an excellent energy density of 84.8 Wh kg−1 and superior cycling performance (98 % capacitance retention after 10,000 cycles). We have investigated the interactions between Ni3S2/CoS2/MoS2 and carbon based nanostructure GQDs employing state-of-the-art Density Functional Theory (DFT) simulations. The interactions between Ni3S2/CoS2/MoS2 and GQDs is not only long range van der Waals interactions, but also chemical interactions involving charge transfer from metal 3d orbital to C 2p orbital of GQDs are also present. Due to this synergic effect, there is enhancement in electronic states near Fermi level which may improve the conductivity of the hybrid structure. Enhanced quantum capacitance, improved conductivity and increased surface area for the hybrid structure may attribute towards superior charge storage performance for the hybrid structures which support experimental data. It is expected that the fabricated, unique, 3D flower NCMS-G-2.5 has potential prospects for developing advanced and high-performance energy storage devices.

Role of Cerium Doping in Petal‐Like NiO Grown Directly over Ni Foam for Enhancing the Super‐Capacitive Behaviour

AbstractWe have synthesized petal‐like structure of cerium doped nickel oxide over the nickel foam using a hydrothermal method at 120 °C. The variation of the doping concentration of cerium from 1–7 mol% was studied to improve the capacitive behaviour. X‐ray diffraction spectroscopy indicates the presence of the NiO phase without any impurities. Field emission scanning electron microscopy shows formation of 3D network by the interconnection of 2D petals morphology. Further, X‐Ray data has been supported by the Raman scattering measurements. X‐ray photoelectron spectroscopy data confirmed the presence of NiO along with traces of Ce3+ which categorically indicate successful doping of Ce3+ in NiO matrix. The electrochemical analysis shows the pseudo‐capacitive behaviour with a specific capacitance of 794.58 F/g at 5 mV/s scan rate. It also shows the cyclic stability of 89.23 % after 800 cycles at a scan rate of 10 mV/s. Electrochemical impedance spectroscopy was carried out to investigate the involved charge transfer kinetics. The 5 mol% doping of cerium into the NiO crystal shows low resistance which provides a shortened path for the charge transfer. It helps to improve the electrochemical behaviour. Thus, the results have shown that cerium doping in NiO can improve the electrochemical performance of the system.

Spectrophotometric studies of low-cost method for determination of ceftriaxone using a novel charge transfer acceptor, N-(2,4-dinitro-1-naphthyl)-p-toluenesulphonamide

BackgroundThis study reports a new, cost-effective and validated method for the determination of ceftriaxone (CFR). The method involved charge transfer (CT) complexation reaction of ceftriaxone (as n-electron donor) and N-(2,4-dinitro-1-naphthyl)-p-toluenesulphonamide {N-(2,4-DN1NL) PTS} as π-electron acceptor to form a complex. Ultraviolet, infrared and 1H NMR spectra of CFR, N-(2,4-DN1NL) PTS and adduct were then studied to predict the site of interaction between the donor and acceptor.ResultThe complex formed had deep golden-yellow colour, having a new absorption band at 440 nm. Molar absorptivity of 1.667 × 105 L M−1 cm−1 was obtained. The complexation reaction was completed at 30 °C optimal temperature within 10 min. Acetonitrile was found to be the best diluting solvent for optimal detector response and the complex was stable (absorbance unchanged) at room temperature for hours. At concentration of 1.708–11.956 µg mL−1, with low limits of detection of 0.143 µg mL−1, Beer’s law was observed. Between-day recovery statistics of CFR from quality control samples were 102.15 ± 0.062 (% RSD = 0.61, n = 12) over three days. The site of interaction of donor and acceptor molecules, as revealed through infrared (IR) and proton nuclear magnetic resonance studies (1H NMR) and the formation of charge transfer complex is through intermolecular hydrogen bonding between the amino group of the donor and the acidic proton of the acceptor. Common tablet excipients, as observed, did not interfere with the analytical method and no significant difference existed between the results of this new method and the high performance liquid chromatographic procedures (p > 0.05) documented in the USP. The new CT procedure described in this paper is not only simple but also fast, accurate and precise. Also, the reactions were carried out at room temperature compared to previously described procedures.ConclusionsThis novel method could therefore be adopted as a fast but cost-effective alternative for the qualitative and quantitative assessment of CFR in its pure and dosage form. It could find usefulness in on-the-spot detection of counterfeit drugs and in field inspections with reliable accurate results that compares with established methods.

Sugar moiety driven adsorption of nucleic acid on graphene quantum dots: Photophysical, thermodynamic and theoretical evidence

Integration of biologically important molecules with graphene quantum dots (GQDs) as a new class of luminescent water-soluble carbon materials, has drawn considerable attention for recent exciting progress on its biomedical applications. In order to avoid toxic semiconductor QDs, GQDs have shown great promise in detection of DNA and other biological applications and hence, fundamental understanding of processes of interactions is important and necessary. The present work establishes the significant role of sugar residue of nucleic acids in adsorption of graphene materials through experimental estimation of binding thermodynamics concomitant with density functional theoretical (DFT) simulation and a detailed evaluation of photophysical parameters. Maximum quenching efficiency of adenosine moiety coupled with the shift in the vibrations of the five-member ring of D-ribose demonstrates the adsorption of DNA on GQDs framework through sugar moieties. The observed experimental results are consistent with the favorable Gibb’s free energy calculated through theoretical simulation. DFT presenting orbital interactions and bonding mechanism of DNAs on GQDs confirms that adsorption on GQDs surface involves charge transfer from nucleobases to GQDs and adenosine, in particular, binds strongly through charge transfer of 0.032e from nitrogen atom to carbon of GQDs. The present investigation will provide insights in understanding the possible role of GQDs in cellular imaging, biosensing and as carriers in targeted drug delivery.

VISIBLE SPECTROPHOTOMETRIC METHODS FOR THE ESTIMATION OF MODAFINIL IN PHARMACEUTICAL FORMULATION

Two simple, sensitive, and fast visible spectrophotometric techniques for quantifying modafinil in marketed dosage form have been proposed. The method A was focussed on the complexation involving charge transfer with picric acid to give pale yellow colored chromogen which shows absorption maxima at 450 nm. In the concentration range of 5-40 μg mL-1, Beer’s law is obeyed with a correlation value of 0.999. The method B depends on the oxidative coupling process with MBTH in the presence of FeCl3 in acidic pH to give green colour chromogen which shows absorption maxima at 657 nm. In the concentration range of 10-50 μg mL-1, Beer’s law was obeyed with a correlation value of 0.999. The developed methodologies have been statistically verified for use in quality control laboratories for pharmaceuticals

Efficient environmental recovery of Au(I) from thiosulfate solution on triphenylphosphine-oxide-modified vermiculite

Natural materials that are economical and environmentally benign are being explored as adsorbent bases for recovering Au(I) from thiosulfate solution via an efficient grafted functional group. In this work, natural vermiculite (VE) modified with triphenylphosphine oxide (TPPO) was used to adsorb Au(I) from thiosulfate solution, and it's gold recovery performance and adsorption mechanism. Fourier transform infrared spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption were used to characterize the adsorbents. TPPO-modified VE (VE-TPPO) showed improved gold adsorption ability at a pH of approximately 10, thiosulfate concentration of approximately 0.1 mol/L and temperature of approximately 25 °C. More than 95% of Au(I) could be recovered, and the loading capacity of Au on VE-TPPO increased with decreasing adsorption temperature, reaching an amount of 4.22 kg/t after once adsorption. TPPO was adsorbed on vermiculite through cationic-π bonds. Au(I) was adsorbed on VE-TPPO by a ligand-exchange mechanism involving charge transfer between PO groups and Au(I). Moreover, the interaction mechanism between TPPO and Au(I) was further validated by density functional theory calculations. The use of natural materials with low cost and environmental impact can make the process of leaching gold with thiosulfate safer and cleaner.

Ti3C2T x MXene anchoring semi-metallic selenium atoms: self-powered photoelectrochemical-type photodetector, hydrogen evolution, and gas-sensing applications

MXenes have demonstrated substantial promise as photocatalysts and electrocatalysts for a variety of applications such as self-powered photoelectrochemical (PEC)-type photodetector, hydrogen evolution reaction (HER), and vapor sensing applications. However, their mechanism is still poorly figured out. Currently, Ti3C2T x MXene suffers from low photoresponsivity, high overpotential, and low sensitivity in such important applications. In order to develop catalytic activity and performances of those devices, modifications must be made to the structure of MXenes to enhance the separation of photogenerated charges, rate of the H+/e− couplings, and surface-active sites. These manipulations of MXenes heavily depend on understanding the mechanism of devices, appropriate modification elements, and the method of modification. This study for the first time reveals a facile solid-state annealing strategy for doping semi-metallic selenium (Se) atoms on Ti3C2T x MXene for self-powered PEC-type photodetector, HER, and vapor sensor applications. The suitable characteristics of Ti3C2T x make it an appropriate substrate to accommodate Se atoms. The well-designed Se-doped Ti3C2 heterojunction including some TiO2 cuboids could exhibit unprecedented photoresponsivity (up to 90 mA W−1) and detectivity (up to 2.0 × 108 cm Hz1/2 W−1) for 420 nm light, HER (−0.7 V at 10 mA cm−2), and gas sensitivity (Z′ = 347 Ω and Z′′ = 150 Ω, for ethanol) in comparison with the pristine Ti3C2T x nanosheets. The acquired promising results can be promoted with some other elements and also be examined in other electrolytes. Then, bring inspiration to the applications involving charge transfer, H+/e− couplings, and surface-active sites.

Enhanced reversible hydrogen storage efficiency of zirconium‐decorated biphenylene monolayer: A computational study

AbstractMetal decorated carbon‐containing two‐dimensional monolayers have been explored as potential hydrogen storage materials because of their open structures which improve the storage capacity. Here, the H2 storage capability of the Zr‐decorated biphenylene nanosheet is studied with the aid of first‐principles calculations. Biphenylene is a recently synthesized ultra‐flat material consisting of different‐sized carbon rings. Zr atom interacts strongly with the monolayer with a binding energy of −4.79 eV due to charge transfer from Zr 3d orbital to C‐2p orbital of biphenylene nanosheet. The hydrogen molecules bind to the Zr‐decorated biphenylene monolayer with an average adsorption energy of −0.4 eV per H2 due to Kubas‐type interactions involving charge transfer between metal d orbital and H‐1s orbital. The Zr decoration helps to adsorb up to 9 hydrogen molecules per metal atom on the monolayer resulting in the H2 uptake of 9.95 wt%, higher than the target of 6.5 wt% set by the Department of Energy (DoE), USA. The high diffusion barrier for the Zr atom prevents metal‐metal clustering. The ab initio molecular dynamics (AIMD) simulations show that the complexes remain stable even at the highest desorption temperature. The present study shows that the Zr‐decorated biphenylene can be considered a prospective two‐dimensional material for reversible hydrogen storage.

Experimental and theoretical investigations of a multiwalled carbon nanotubes/SnO2/polyaniline ternary nanohybrid electrode for energy storage

In the present work, we report synthesis of ternary hybrid of multiwalled carbon nanotubes/SnO2/polyaniline (MSP) for energy storage application. The various characterization studies such as X-ray diffraction (XRD-structural confirmation), Transmission electron microscopy (TEM-morphology), Fourier transform infrared microscopy (FTIR) and Raman (molecular confirmation), and X-ray photoelectron microscopy (XPS-elemental and oxidation state) confirm the ternary hybrid formation. Three-electrode system with the use of 1 M H2SO4 electrolyte reveals the electrochemical performance of the ternary hybrid. The MSP electrode demonstrates the specific capacitance value of 221 F g−1 at the current density of 2 A g−1. Also, it shows outstanding capacitance retention (95%) with 100% coulombic efficiency for 1000 charge/discharge cycles. From Density Functional Theory (DFT) simulations, enhancement of electronic states near Fermi level and increment of quantum capacitance for the ternary hybrid justifies the experimental enhancement of charge storage performance of MSP. The interactions between polyaniline (PANI) and carbon nanotubes /SnO2 involves charge transfer from H 1s and N 2p orbitals of PANI to C 2p orbital of carbon nanotubes.