Engineering the physical properties and photocatalytic activities of a ß-ketoenamine COF using continuous flow synthesis.

Covalent Organic Frameworks (COF) having conjugated backbone are an interesting class of metal-free, visible light active, heterogeneous photocatalysts. Interestingly, synthesis of COF using continuous flow process has emerged as an efficient, alternative method when compared to the traditional batch process. Here, we demonstrate the possibility to engineer the physical properties and hence the adsorption and catalytic activities of a ß-ketoenamine COF by varying monomer flow rate and microreactor design during the continuous flow synthesis. Crystallinity of the COF increases on varying the monomer flow rate from 100 (S-100) to 500 (S-500) and up to 1000 µLmin-1 (S-1000), in an S-shaped microreactor, resulting in an enhanced surface area: 525, 722 and 1119 m2g-1 respectively. The photophysical properties of the COF are also found to vary significantly with the change in flow synthesis conditions. S-1000 is characterized by the highest adsorption of MB, due to its high surface area and accessible pores. On the other hand, S-500 shows the highest photocurrent, a low recombination of photogenerated charges and the lowest charge transfer resistance. Thus, S-500 is found to be the best photocatalyst for the removal of a model pollutant (methylene blue, MB). Further, enhanced photocatalytic removal of MB using S-500 could be achieved by performing the photocatalysis in continuous flow.

Fine-tuning covalent organic frameworks for structure-activity correlation via adsorption and catalytic studies.

In applications utilizing Covalent Organic Frameworks (COFs) for adsorption, the interplay between crystallinity (vis-à-vis surface area) and active sites still remains ambiguous. To address this, the present study introduces three isoreticular COFs-COP-N18 (covalent organic polymer with short-range order), COF-N18 (COF having long-range order), and COF-N27 (semicrystalline COF with pyridyl heteroatoms)-to explore this duality. Through systematic variations in structural order, pore volume, and pore-wall nitrogen content, we aim to establish a structure-activity relationship (SAR) for these COFs via adsorption and catalysis, using CO2 and I2 as probes. Our investigation highlights the positive influence of crystallinity, surface area, and pore volume in adsorption as well as catalysis. However, the presence of heteroatoms manifests complex behavior in CO2 adsorption and CO2 cycloaddition reactions with epoxides. COF-N18 and COF-N27 showed comparable CO2 uptake capacities at different temperatures (273, 293, and 313 K) and ∼1 bar pressure. Additionally, CO2 cycloaddition reactions were performed with substrates possessing different polarities (epichlorohydrin, 1,2-epoxydodecane) to elucidate the role of COF surface polarity. Further investigation into iodine adsorption was performed to understand the impact of COF structural features on the modes of adsorption and adsorption kinetics. Improvements in COF-crystallinity results in faster average iodine uptake rate at 80% (K80% = 1.79 g/h) by COF-N18. Whereas, heteroatom doping slows down iodine adsorption kinetics (0.35 g/h) by prolonging the adsorption process up to 72 h. Overall, this study advances our understanding of COFs as adsorbents and catalysts, providing key insights into their SAR while emphasizing structural fine-tuning as a key factor for impactful environmental applications.

Systematic Thiol Decoration in a Redox-Active UiO-66-(SH)2 Metal-Organic Framework: A Case Study under Oxidative and Reductive Conditions.

The practical applicability of thiolated metal-organic frameworks (MOFs) remains challenging due to their low crystallinity and transient stability. Herein, we present a one-pot solvothermal synthesis process using varying ratios of 2,5-dimercaptoterephthalic acid (DMBD) and 1,4-benzene dicarboxylic acid (100/0, 75/25, 50/50, 25/75, and 0/100) to prepare stable mixed-linker UiO-66-(SH)2 MOFs (ML-U66SX). For each variant, the effects of different linker ratios on the crystallinity, defectiveness, porosity, and particle size have been discussed in detail. In addition, the impact of modulator concentration on these features has also been described. The stability of ML-U66SX MOFs was investigated under reductive and oxidative chemical conditions. The mixed-linker MOFs were used as sacrificial catalyst supports to highlight the interplay of template stability on the rate of the gold-catalyzed 4-nitrophenol hydrogenation reaction. The release of catalytically active gold nanoclusters originating from the framework collapse decreased with the controlled DMBD proportion, resulting in a 59% drop in the normalized rate constants (9.11-3.73 s-1 mg-1). In addition, post-synthetic oxidation (PSO) was used to further probe the stability of the mixed-linker thiol MOFs under harsh oxidative conditions. Following oxidation, the UiO-66-(SH)2 MOF underwent immediate structural breakdown, unlike other mixed-linker variants. Along with crystallinity, the microporous surface area of the post-synthetically oxidized UiO-66-(SH)2 MOF could be increased from 0 to 739 m2 g-1. Thus, the present study delineates a mixed-linker strategy to stabilize the UiO-66-(SH)2 MOF under harsh chemical conditions through meticulous thiol decoration.

Correction: Engineering the morphology of palladium nanostructures to tune their electrocatalytic activity in formic acid oxidation reactions.

[This corrects the article DOI: 10.1039/D0NA00798F.].

Synthesis of Metal Nanostructures Using Supercritical Carbon Dioxide: A Green and Upscalable Process.

Metallic nanostructures have numerous applications as industrial catalysts and sensing platforms. Supercritical carbon dioxide (scCO2 ) is a green medium for the scalable preparation of nanomaterials. Supercritical fluid reactive deposition (SFRD) and other allied techniques can be employed for the mass production of metal nanostructures for various applications. The present article reviews the recent reports on the scCO2 -assisted preparation of zero-valent metal nanomaterials and their applications. A brief description of the science of pure supercritical fluids, especially CO2 , and the basics of binary mixtures composed of scCO2 and a low volatile substance, e.g., an organometallic precursor are presented. The benefits of using scCO2 for preparing metal nanomaterials, especially as a green solvent, are also being highlighted. The experimental conditions that are useful for the tuning of particle properties are reviewed thoroughly. The range of modifications to the classical SFRD methods and the variety of metallic nanomaterials that can be synthesized are reviewed and presented. Finally, the broad ranges of applications that are reported for the metallic nanomaterials that are synthesized using scCO2 are reviewed. A brief summary along with perspectives about future research directions is also presented.

Engineering the morphology of palladium nanostructures to tune their electrocatalytic activity in formic acid oxidation reactions.

Pd nanomaterials can be cheaper alternative catalysts for the electrocatalytic formic acid oxidation reaction (FAOR) in fuel cells. The size and shape of the nanoparticles and crystal engineering can play a crucial role in enhancing the catalytic activities of Pd nanostructures. A systematic study on the effect of varying the morphology of Pd nanostructures on their catalytic activities for FAOR is reported here. Palladium nanoparticles (Pd0D), nanowires (Pd1D) and nanosheets (Pd2D) could be synthesized by using swollen liquid crystals as 'soft' templates. Swollen liquid crystals are lyotropic liquid crystals that are formed from a quaternary mixture of a surfactant, cosurfactant, brine and Pd salt dissolved in oil. Pd1D nanostructures exhibited 2.7 and 19 fold higher current density than Pd0D and Pd2D nanostructures in the FAOR. The Pd1D nanostructure possess higher electrochemically active surface area (ECSA), better catalytic activity, stability, and lower impedance to charge transfer when compared to the Pd0D and Pd2D nanostructures. The presence of relatively higher amounts of crystal defects and enriched (100) crystal facets in the Pd1D nanostructure were found to be the reasons for their enhanced catalytic activities.

Preparation, characterization and in vitro cytotoxicity of Fenofibrate and Nabumetone loaded solid lipid nanoparticles.

There is an increasing attention on solid lipid nanoparticles (SLNs) due to their high biocompatibility and ability to enhance bioavailability for poorly water-soluble drugs. Preparation of SLNs that are capable of high drug loading and sustained drug release through hot melt sonication method is reported here. SLNs of palmitic acid and stearic acid loaded with poorly water-soluble drugs, viz. fenofibrate (FF) and nabumetone (NBT) having spherical morphology and average particle size below 200 nm were prepared. Poloxamer 407 and pluronic® F-127 were used as surfactants. Particle size and spherical morphology was confirmed by dynamic light scattering, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The chemical, crystal, and thermal properties of SLNs were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry, respectively. The palmitic acid-poloxamer 407 SLNs could entrap upto 13.8% FF with 80% entrapment efficiency while the stearic acid-pluronic® F-127 SLNs entrapped 13.6% NBT with 89% entrapment efficiency. The drug loaded in SLNs showed controlled release up to 3 days as confirmed by in-vitro drug release profile. Moreover, the drug loaded SLNs did not show any toxicity on macrophage cell line proving the use of these formulations as control drug delivery vehicles for the studied drugs.

N-Amino-7-azaindole as the N,N'-Bidentate Directing Group: Ruthenium-Catalyzed Oxidative Annulation of N-(7-Azaindole)benzamides with Alkynes via C-H Bond Activation.

We report a new application of N-amino-7-azaindole as a new bidentate-directing group for [Ru(p-cymene)Cl2]2-catalyzed C(sp2)-H alkenylation/annulation of N-(1H-pyrrolo[2,3-b]pyridin-1-yl)benzamides with internal alkynes to afford N-isoquinolono-7-azaindole via the formation of C-C and C-N bonds. The reaction shows a wide range of substrate scope with different symmetrical and unsymmetrical alkynes, affording the desired product in good to excellent yields. In the case of unsymmetrical alkynes, a highly regioselective product was obtained, which was confirmed by single-crystal X-ray crystallography. A new ruthenium-4-methyl-N-(1H-pyrrolo[2,3-b]pyridin-1-yl)benzamide complex was isolated, and its structure was confirmed by single-crystal X-ray crystallography.

Engineering the Morphology and Particle Size of High Energetic Compounds Using Drop-by-Drop and Drop-to-Drop Solvent-Antisolvent Interaction Methods.

Morphology-controlled precipitation of three powerful organic high energetic compounds (HECs) viz. cyclotrimethylenetrinitramine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 2-methyl-1,3,5-trinitrobenzene (TNT) was achieved by two different processes, namely, drop-by-drop (DBD) and drop-to-drop (DTD) solvent-antisolvent interaction methods. Effect of different experimental parameters on the mean size and morphology of the prepared submicron-sized particles of HECs was investigated thoroughly. The DBD method favors the formation of nanosized particles of RDX and TNT at lower concentrations (5 mM). However, a significant increase in the mean particle size occurred at higher concentrations (25 and 50 mM). Formation of facetted crystals of RDX, HMX, and nanorods of TNT was observed at higher concentrations because of the interaction of crystal facets with the antisolvent. Relatively, smaller sized, spherical particles of RDX and HMX could be prepared through the DTD method even at higher concentrations (25 mM). The DTD method is a continuous process and hence is a facile method for industrial applications. X-ray diffraction and Fourier transform infrared spectroscopy studies revealed that RDX, HMX and TNT were precipitated in their most stable polymorphic forms α, ß, and monoclinic, respectively. Differential scanning calorimetry showed that the thermal response of the nano-HECs was similar to the respective raw-HECs. A slight decrease in crystallinity and the melting point was observed because of the decrease in the mean particle size.

Enhancing the Solubility of Fenofibrate by Nanocrystal Formation and Encapsulation.

Development of techniques to enhance bioavailability of drugs having poor water solubility is a big challenge for pharmaceutical industry. Solubility can be enhanced by particle size reduction and encapsulation using hydrophilic polymers. Fenofibrate (FF) is a drug for regulating lipids. Multi-fold enhancement in solubility of FF has been achieved by nanocrystal formation in the present study. Nanoparticles were prepared by an evaporation-assisted solvent-antisolvent interaction (EASAI) approach. Water-soluble polymers, viz. polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and hydroxypropyl methylcellulose (HPMC), were used to encapsulate and thus control the particle size of FF nanocrystals. Spherical particles having average particle size well below 30 nm could be prepared under optimum conditions. Almost complete release of the drug molecules from the polymer-stabilized nanocrystals within 2 h was clearly evident from the in vitro drug release studies. Infrared (FTIR) spectroscopy indicated the absence of solvent impurities and any strong interaction between the drug and stabilizers. The polymorphic form of raw-FF was retained in the nanoparticles as per the X-ray diffraction (XRD) patterns. Lower crystallinity of the nanoformulated samples compared to raw-FF was confirmed by differential scanning calorimetric (DSC) studies.

Solid lipid nanoparticles for the controlled delivery of poorly water soluble non-steroidal anti-inflammatory drugs.

Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (IBP) are among the most prescribed drugs across the globe. However, most NSAIDs are insoluble in water leading them to have poor bioavailability and erratic absorption. Moreover, NSAIDs such as IBP and ketoprofen (KP) have to be administered very frequently due to their short plasma half-life leading to side effects. Controlled release formulations of IBP, KP and nabumetone (NBT) based on solid lipid nanoparticles (SLNs) were successfully synthesised in the present study to solve the above-mentioned challenges that are associated with NSAIDs. SLNs were prepared in two steps; hot-melt homogenization followed by sonication to formulate SLNs with spherical morphology. While capmul® GMS-50K (capmul) was used as the lipid due to the high solubility of the studied drugs in it, gelucire® 50/13 (gelucire) was used as the surfactant. It was found that particle size was directly proportional to drug concentration and inversely proportional to surfactant concentration, volume of water added and temperature of water. Ultrasonication in a pulse mode with optimum duration of 15min was essential to obtain smaller nanoparticles through the formation of a nanoemulsion. Drug loaded SLNs with small particle size and narrow size distribution with good solid loading, encapsulation efficiency and drug loading percentage could be prepared using the optimised conditions. SLNs prepared at the optimised condition were characterized thoroughly by using different techniques such as dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The cytotoxicity results showed that the prepared SLNs are non-toxic to Raw cell line. The drugs IBP, KP and NBT showed 53, 74 and 69% of percentage entrapment efficiency with drug loading of 6, 2 and 7% respectively. Slow, steady and sustained drug release was observed from the SLNs for over 6days.

A dataset for preparing pristine graphene-palladium nanocomposites using swollen liquid crystal templates.

Pristine graphene (G) has not received much attention as a catalyst support, presumably due to its relative inertness as compared to reduced graphene oxide (RGO). In the present work, we used swollen liquid crystals (SLCs) as nano-reactors for graphene-palladium nanocomposites synthesis. The 'soft' confinement of SLCs directs the growth of palladium (Pd) nanoparticles over the G sheets. In this dataset we include all the parameters and details of different techniques used for the characterization of G, SLCs and synthesized G-Pd nanocomposites. The synthesized G-palladium nanocomposites (Pd-G) exhibited improved catalytic activity compared with Pd-RGO and Pd nanoparticles, in the hydrogenation of nitrophenols and C-C coupling reactions.

Dendritic Polynitrato Energetic Motifs: Development and Exploration of Physicochemical Behavior through Theoretical and Experimental Approach.

Considering the fundamental and most desirable characteristics of energetic materials, a series of 1,2,3-triazole-based heterocyclic energetic motifs nicely tuned with nitrato (-ONO2) functionality were synthesized by a microwave-assisted environmental friendly synthetic approach with good yields. Thermal stability and the nature of evolved gases on decomposition of structurally characterized energetic motifs were analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) analysis and Fourier transform infrared coupled with TGA-DSC. The explosiveness of these motifs was explored by calculation of enthalpy of formation and density employing density functional theory, and the detonation performances (detonation pressure and velocity) were explored using EXPLO5_V6.03. All of these compounds were calculated to have better oxygen balance (-36 to -52%) as compared to that of trinitrotoluene (-74%). Most of the nitrate ester derivatives were found to exhibit low impact sensitivities, high densities, good thermal stabilities, and promising detonation properties, and PN 3 was observed to be a superior candidate in terms of its energetic characteristics. Hence, the experimental and theoretical outcomes strongly reflect that the present approach of developing dendritic high energetic materials bearing green explosive characteristics might be a potential pathway for designing and synthesizing green explosives with desired characteristics.

Unusual anti-leukemia activity of nanoformulated naproxen and other non-steroidal anti-inflammatory drugs.

The non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used pharmaceuticals worldwide. Interestingly, many of them have significant anticancer properties too. However, the poor water solubility of certain NSAIDs limits their application for cancer treatment. Nanosizing of such drugs can help to improve the solubility and this may result in enhanced anticancer activities too. Moreover, over dosages and the accompanying side effects of NSAIDs can be minimized by improving their solubility and bioavailability. Successful nanoformulation of three NSAIDs: ibuprofen (IBP), ketoprufen (KP) and naproxen (NAP) using a novel evaporation assisted solvent-antisolvent interaction (EASAI) method is reported here. Three water soluble and biocompatible polymers: polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and hydroxypropyl methylcellulose (HPMC) were used to stabilize the drug nanoparticles. Particles having spherical morphology with average size below 30nm were thoroughly characterized using dynamic light scattering and field emission scanning electron microscopy (FESEM) imaging. The nanoformulation resulted in ten to fifteen fold improvements in the solubility and significant enhancement in the in-vitro drug release profiles of the NSAIDs. Anticancer screening of the nanoformulated NSAIDs against five different cancer cell lines such as MCF-7 (Human breast cancer cell line), (Human pancreatic cancer cell line) MIA-PA-CA-2, (Human colon cancer cell line) HT-29, (Human leukemia cell line) Jurkat and (human ovarian carcinoma cell line) A2780 was performed. All the nanoformulated samples showed improved anticancer activity against the Leukemia cancer cell line, out of which NAP-PVP showed the highest anti-cancer activity. The anti-Leukemia activity of NAP-PVP was more than twice that of doxorubicin which is a standard anticancer drug.

Tuning the surface enhanced Raman scattering and catalytic activities of gold nanorods by controlled coating of platinum.

Galvanic replacement of silver (Ag) by platinum (Pt) on bi-metallic nanorods (NRs) having gold (Au) core and silver shell (Au@Ag) resulted in discontinuous coating of Pt over Au (Au@Pt-DC) NRs. However, a novel method has been developed in this work for the preparation of Au NRs having smooth and continuous coating of Pt (Au@Pt-C NRs) using galvanic replacement reaction of Au@Ag NRs in presence of sulphuric acid. Selective blocking by the bisulfate ions that are adsorbed on Pt surface, preventing Pt on Pt deposition seems to be the mechanism of formation of Au@Pt-C NRs. Effect of the nature of Pt shell (i.e. whether continuous or discontinuous) on SERS activity of the NRs was investigated with methylene blue (MB) as a reporter molecule. The specific enhancement of the Raman signals were in the order Au@ Pt-C NRs