Crystal Engineering: A Powerful Tool towards Designing Pharmaceutical Solids with Desirable Physicochemical Properties

Nowadays various techniques have been applied for the improvement of physicochemical properties such as solubility, bioavailability, stability and hygroscopic nature of pharmaceutical solids without effecting the biochemical composition of the active pharmaceutical ingredients (API). Supramolecular approach specially the crystal engineering technique is one of the best techniques which play an important role to improve the physico-chemical, thermal and mechanical properties of drug molecules. Crystal engineering approach offers a number of routes such as co-crystallization, polymorphism, hydrate and salt formation with the help of which drug molecules with good physico-chemical behavior can be prepared. This article covers the concept of supramolecular chemistry and crystal engineering approach for the preparation of co-crystals and their application in pharmaceutical industries

Characterization of epitaxial GaAs MOS capacitors using atomic layer-deposited TiO2/Al2O3 gate stack: study of Ge auto-doping and p-type Zn doping

Electrical and physical properties of a metal-oxide-semiconductor [MOS] structure using atomic layer-deposited high-k dielectrics (TiO2/Al2O3) and epitaxial GaAs [epi-GaAs] grown on Ge(100) substrates have been investigated. The epi-GaAs, either undoped or Zn-doped, was grown using metal-organic chemical vapor deposition method at 620°C to 650°C. The diffusion of Ge atoms into epi-GaAs resulted in auto-doping, and therefore, an n-MOS behavior was observed for undoped and Zn-doped epi-GaAs with the doping concentration up to approximately 1017 cm-3. This is attributed to the diffusion of a significant amount of Ge atoms from the Ge substrate as confirmed by the simulation using SILVACO software and also from the secondary ion mass spectrometry analyses. The Zn-doped epi-GaAs with a doping concentration of approximately 1018 cm-3 converts the epi-GaAs layer into p-type since the Zn doping is relatively higher than the out-diffused Ge concentration. The capacitance-voltage characteristics show similar frequency dispersion and leakage current for n-type and p-type epi-GaAs layers with very low hysteresis voltage (approximately 10 mV)

Functionalized Graphene-Incorporated Cupric Oxide Charge-Transport Layer for Enhanced Photoelectrochemical Performance and Hydrogen Evolution

The production of hydrogen (H2) through photoelectrochemical water splitting (PEC-WS) using renewable energy sources, particularly solar light, has been considered a promising solution for global energy and environmental challenges. In the field of hydrogen-scarce regions, metal oxide semiconductors have been extensively researched as photocathodes. For UV-visible light-driven PEC-WS, cupric oxide (CuO) has emerged as a suitable photocathode. However, the stability of the photocathode (CuO) against photo-corrosion is crucial in developing CuO-based PEC cells. This study reports a stable and effective CuO and graphene-incorporated (Gra-COOH) CuO nanocomposite photocathode through a sol-gel solution-based technique via spin coating. Incorporating graphene into the CuO nanocomposite photocathode resulted in higher stability and an increase in photocurrent compared to bare CuO photocathode electrodes. Compared to cuprous oxide (Cu2O), the CuO photocathode was more identical and thermally stable during PEC-WS due to its high oxidation number. Additionally, the CuO:Gra-COOH nanocomposite photocathode exhibited a H2 evolution of approximately 9.3 µmol, indicating its potential as a stable and effective photocathode for PEC-WS. The enhanced electrical properties of the CuO:Gra-COOH nanocomposite exemplify its potential for use as a charge-transport layer

Controlled synthesis and characterization of the elusive thiolated Ag-55 cluster

A stable, Ag-55 cluster protected with 4-(tert-butyl) benzyl mercaptan (BBSH) was synthesized which exhibits two prominent absorption bands with maxima at 2.25 and 2.81 eV. A molecular ion peak at m/z 11500 +/- 20 in matrix assisted laser desorption ionization mass spectrum (MALDI MS), assigned to Ag-55(BBS)(31) was observed. Electrospray ionization (ESI MS) shows a prominent trication along with higher charged species. An analogous Ag-55(PET) (31) (PET = 2-phenylethanethiol, in the thiolate form) was also synthesized under optimized conditions which proves the amenability of this cluster and the synthetic methodology to other ligands

Structural Adaptation of Ni₄O₄ Units To Form Cubane, Open Dicubane, Dimeric Cubane, and One-Dimensional Polymeric Cubanes: Magnetostructural Correlation of Ni₄ Clusters

The complexation reactions of a tripodal chelating ligand, [3,5-bis­(2-amino-ethyl)-[1,3,5]­triazinan-1-yl]-methanol (<b>L</b>), which is produced by the <i>in situ</i> transformation of 1,3,6,8-tetraazatricyclo­[4.4.1.1^3,8]­dodecane (<b>L</b>^<b>1</b>) with Ni­(NO₃)₂·6H₂O has been explored in the presence of ammonium salts of inorganic and organic anions. These reactions resulted in four crystalline complexes [Ni₄(<b>L</b>)₂­(μ₃-OH)₂­(NCS)₄]·4H₂O (<b>1</b>), [Ni₄(<b>L</b>)₂­(μ₂-N₃)₄­(N₃)₂]·2H₂O (<b>2</b>), [Ni₈(<b>L</b>)₄­(μ₃-OH)₄­(BDC)₃­(H₂O)₄]·BDC·28­(H₂O) (<b>3</b>, BDC = 1,4-benzene dicarboxylate) and {[Ni₄(<b>L</b>)₂­(μ₃-OH)₂­(NDS)₂­(H₂O)₂]·NDS·11­(H₂O)}_<i>n</i> (<b>4</b>, NDS = naphthalene-1,5-disulfonate). The crystal structure analyses of <b>1</b>–<b>4</b> reveal that all contain Ni­(II) clusters, which act as secondary building units to generate higher order aggregates. The complexes <b>1</b>, <b>3</b>, and <b>4</b> contain exclusively Ni₄ cubane units: a discrete cubane in <b>1</b>, a dimer of cubanes linked by BDC in <b>3</b>, and cubanes linked in one dimension by NDS to form a 1D-coordination polymer in <b>4</b>. Interestingly, complex <b>2</b> exhibits an open dicubane with two missing vertices. Although a plethora of water molecules had been included in their crystal lattices, the crystals were found to be stable even at room temperature. The water molecules govern the overall crystal packing by the formation of strong hydrogen bonds and clusters. Large clusters of water such as (H₂O)₂₈ and (H₂O)₁₆ were observed in <b>3</b> and <b>4</b>, respectively, while dimers of water were observed in <b>1</b> and <b>2</b>. Magnetic susceptibility (χ_M) measurements in the temperature range of 2–300 K on <b>1</b>–<b>3</b> reveal that the metal centers are ferromagnetically coupled in all three depending on their respective exchange pathways. Interestingly, the room temperature (300 K) χ_M<i>T</i> values increase as the molecular aggregation increases from discrete cubane (5.5 cm³ K mol^–1) to face sharing open dicubane (6.21 cm³ K mol^–1) to connected dicubane (11.36 cm³ K mol^–1). The modes of bridging by ^–OH, N₃^–, and BDC and their bond angles with paramagnetic Ni­(II) centers clearly explained the overall ferromagnetism operating in the spin clusters

p-i-n Structured Semitransparent Perovskite Solar Cells with Solution-Processed Electron Transport Layer

p-i-n structured semitransparent perovskite solar cells have already been established as promising energy harvesting devices for building-integrated photovoltaics and flexible solar cells due to high transparency and low-cost fabrication. In this study, solution based p-i-n structured semitransparent perovskite solar cells (PSCs) have been developed using thin silver (Ag), zinc oxide (ZnO), and aluminium (Al)-doped ZnO nanoparticles (AZO) as buffer layers in addition to PCBM as an electron transport layer (ETL). The thickness of the ZnO and AZO layers are around ~100 nm. In the case of the thin Ag layer, poor interfacial band alignment and less transparency yield device performance with an inferior PCE of 2.53% when illuminated from the top electrode side. On the contrary, Al-doped ZnO possesses excellent optoelectronic performance as a buffer layer for their better electronic conductivity and interfacial band alignment and yield a photovoltaic device characteristic with a power conversion efficiency (PCE) of 5.87% when illuminated from the top electrode side, whereas the standard device with a metal electrode shows a PCE of 6.4%. The semitransparent device also has an average transparency of 21.8% in the visible region. Graphic Abstract: Inverted structure semitransparent perovskite solar cells have been developed for flexible and building integrated photovoltaic (BIPV) applications. Solution processed perovskite solar cells with a power conversation efficiency of 5.87% and visible transmittance of 21.8% make an excellent candidate for BIPV and smart windows. Aluminum-doped zinc oxide (AZO) nanoparticles are found very effective buffer layer for the sputter grown top electrode over PCBM layer to reduce the interface damage and enhanced the overall photovoltaic performance. [Figure not available: see fulltext.]</p

Efficient Plastic Recycling and Remolding Circular Economy Using the Technology of Trust–Blockchain

Global plastic waste is increasing rapidly. In general, densely populated regions generate tons of plastic waste daily, which is sometimes disposed of on land or diverged to sea. Most of the plastics created in the form of waste have complex degradation behavior and are non-biodegradable by nature. These remain intact in the environment for a long time span and potentially originate complications within terrestrial and marine life ecosystems. The strategic management of plastic waste and recycling can preserve environmental species and associated costs. The key contribution in this work focuses on ongoing efforts to utilize plastic waste by introducing blockchain during plastic waste recycling. It is proposed that the efficiency of plastic recycling can be improved enormously by using the blockchain phenomenon. Automation for the segregation and collection of plastic waste can effectively establish a globally recognizable tool using blockchain-based applications. Collection and sorting of plastic recycling are feasible by keeping track of plastic with unique codes or digital badges throughout the supply chain. This approach can support a collaborative digital consortium for efficient plastic waste management, which can bring together multiple stakeholders, plastic manufacturers, government entities, retailers, suppliers, waste collectors, and recyclers.</p

Kinetics and mechanism of interaction of Pt(II) complex with bio-active ligands and <i>in vitro</i> Pt(II)-sulfur adduct formation in aqueous medium: bio-activity and computational study

<p>Kinetics of interaction between [Pt(pic)(H₂O)₂](ClO₄)₂, <b>2</b> (where pic = 2-aminomethylpyridine) with the selected ligands DL-methionine (DL-meth) and DL-penicillamine (DL-pen) have been studied spectrophotometrically in aqueous medium separately as a function of [<b>2</b>] as well as [ligand], pH and temperature at constant ionic strength. The association equilibrium constants (<i>K</i>_E) for the outer sphere complex formation have been evaluated together with the rate constants for the two subsequent steps. Activation parameters (enthalpy of activation ΔH^≠ and entropy of activation ΔS^≠) were calculated from the Eyring equation. An associative mechanism of substitution is proposed for both reactions on the basis of the kinetic observations, evaluated activation parameters, and spectroscopic data. Structural optimizations, HOMO-LUMO energy calculation, and Natural Bond Orbital (NBO) analysis of <b>2</b>–<b>4</b> were carried out with Density Functional Theory. Bonding mode of thiol and thio-ether is confirmed by spectroscopic analyses and NBO calculation. Cytotoxic properties of <b>2</b>–<b>4</b> were explored on A549 carcinoma cell lines; DNA-binding properties of the complexes were also investigated by gel electrophoresis.</p

Tin oxide for optoelectronic, photovoltaic and energy storage devices: a review

Tin dioxide (SnO2), the most stable oxide of tin, is a metal oxide semiconductor that finds its use in a number of applications due to its interesting energy band gap that is easily tunable by doping with foreign elements or by nanostructured design such as thin film, nanowire or nanoparticle formation, etc., and its excellent thermal, mechanical and chemical stability. In particular, its earth abundance and non-toxicity make it very attractive for use in a number of technologies for sustainable development such as energy harvesting and storage. This article attempts to review the state of the art of synthesis and properties of SnO2, focusing primarily on its application as a transparent conductive oxide (TCO) in various optoelectronic devices and second in energy harvesting and energy storage devices where it finds its use as an electron transport layer (ETL) and an electrode material, respectively. In doing so, we discuss how tin oxide meets the requirements for the above applications, the challenges associated with these applications, and how its performance can be further improved by adopting various strategies such as doping with foreign metals, functionalization with plasma, etc. The article begins with a review on the various experimental approaches to doping of SnO2 with foreign elements for its enhanced performance as a TCO as well as related computational studies. Herein, we also compare the TCO performance of doped tin oxide as a function of dopants such as fluorine (F), antimony (Sb), tantalum (Ta), tungsten (W), molybdenum (Mo), phosphorus (P), and gallium (Ga). We also discuss the properties of multilayer SnO2/metal/SnO2 structures with respect to TCO performance. Next, we review the status of tin oxide as a TCO and an ETL in devices such as organic light emitting diodes (OLEDs), organic photovoltaics (OPV), and perovskite solar cells (including plasma treatment approaches) followed by its use in building integrated photovoltaic (BIPV) applications. Next, we review the impact of SnO2, mainly as an electrode material on energy storage devices starting from the most popular lithium (Li)-ion batteries to Li–sulfur batteries and finally to the rapidly emerging technology of supercapacitors. Finally, we also compare the performance of doped SnO2 with gallium (Ga) doped zinc oxide (ZnO), the main sustainable alternative to SnO2 as a TCO and summarize the impact of SnO2 on circular economies and discuss the main conclusions and future perspectives. It is expected that the review will serve as an authoritative reference for researchers and policy makers interested in finding out how SnO2 can contribute to the circular economy of some of the most desired sustainable and clean energy technologies including the detailed experimental methods of synthesis and strategies for performance enhancement