Engineering mechanical compliance in polymers and composites for the design of smart flexible sensors.

Polymers are one of the most popular materials for next-generation flexible sensing device fabrication due to their tunable mechanical and electrical properties. A series of prior research studies in the field of smart flexible and wearable sensing illustrates the potential of various polymer and composite materials to be applied in sensor development. In this direction, mechanical compliance plays a vital role as it ensures the stability and reliability of the fabricated sensor. Therefore, engineering mechanical compliance for the development of smart flexible solutions has emerged as a significant area of research. Furthermore, the usage of flexible sensing devices is rapidly increasing in the field of healthcare devices and robotic automation. This feature article summarizes the relevant contributions of the authors in the field of engineered polymers and composites for flexible sensor development with a focus on healthcare and physical sensing applications. We discuss the polymer and composite materials, their characteristics, fabrication technologies, finite element method analysis, and examples of flexible physical sensors, i.e. pressure, strain, and temperature sensors, for various wearable healthcare applications and robotic automation. Finally, we discuss examples of multi-sensory systems having flexible sensors.

Synthon Approach in Crystal Engineering to Modulate Physicochemical Properties in Organic Salts of Chlorpropamide.

The formulation of drug with improved bioavailability is always challenging and indispensable in the field of pharmaceutics. The control of intermolecular interactions via crystal engineering approach and solid-state molecular recognition results in the formation of active drug molecules with modulated pharmacological benefits. Therefore, with the aim to improve the solubility and dissolution rate of the drug chlorpropamide (CPA), the mechanochemical liquid-assisted grinding (LAG) of the drug with several pharmaceutically accepted excipients was performed. This contributed to the discovery of six novel solid phases, namely salts, salt cocrystals and salt cocrystal hydrate─the salt of CPA with 3, 4-diaminopyridine (DAP); salt and salt cocrystal (SC) polymorph (Z″=3) with 1, 4-diazabicyclo [2.2.2] octane (DABCO); a salt, SC polymorph (Z″=9), and a SC hydrate (Z″=9) with piperazine (PIP). The formation of these salts and salt cocrystals are mainly guided by the strong hydrogen bonds with tunable strength having high electrostatic contribution. This attractive interaction brings the donor and the acceptor atoms close to each other for a facile proton transfer. Furthermore, the conformational constraints on the drug molecules, provided by the excipients via strong and directional hydrogen bonds, are quite impressive as this leads to the identification and characterization of "new conformational isomers" for the CPA molecules. The new crystalline phases exhibit enhanced intrinsic dissolution rate in comparison to that of the pure drug, the magnitude being 7, 131, and 120 folds for CPADAP, CPADABCO_II, and CPAPIP_III, respectively. Furthermore, it is interesting to note that the order of solubility is enhanced by 2.7-, 3-, and 7-fold, respectively, for the abovementioned salts. This also mirrors the trends in the magnitude of the binding energy, the higher magnitude being reflected in the lower solubility. Additionally, the in vivo experiments performed in SD rats results in the enhancement of the magnitude of the pharmacokinetic properties, when compared to the pristine drug. The concentration of the drug in CPADABCO_II and CPAPIP_III formulations exhibits 6- and 4-fold increments, respectively. Indeed, these results corroborate to the trends observed in the structural characterization, intermolecular energy calculations, solubility, and in vitro dissolution assessments.

In Situ Crystallization, Differential Growth, and Multicolor Emission of Silver Nanoclusters.

The real-time monitoring of the stepwise growth process of the molecular crystal reveals a conclusive understanding of the morphological evolution, which otherwise remains elusive during the conventional crystallization processes. Herein, we report the in situ crystallization of silver nanoclusters (AgNCs) with special emphasis on their differential growth and multicolor emissive properties. A subtle variation of the methanol (MeOH) proportion in the reaction mixture induces the differential growth of these AgNCs, and thereby, a dramatic modulation in their optical properties was observed. Additionally, by increasing the temperature of the reaction (from a low temperature ice bath to 25 °C), an uncontrolled formation of AgNCs along with metallic silver nanoparticles (AgNPs) was observed, which was primarily induced by accelerating the reaction kinetics. We hope that this investigation comprehensively uncovers the serious bottlenecks of the conventional crystallization processes by showcasing systematic monitoring of structural evolution to the higher-ordered crystalline state.

An Atom-Economic Method for 1,2,3-Triazole Derivatives via Oxidative [3 + 2] Cycloaddition Harnessing the Power of Electrochemical Oxidation and Click Chemistry.

An electrochemical method was developed to accomplish the reagentless synthesis of 4,5-disubstituted triazole derivatives employing secondary propargyl alcohol as C-3 synthon and sodium azide as cycloaddition counterpart. The reaction was conducted at room temperature in an undivided cell with a constant current using a pencil graphite (C) anode and stainless-steel cathode in a MeCN solvent system. The proposed reaction mechanism was convincingly established by carrying out a series of control experiments and further supported by electrochemical and density functional theory (DFT) studies.

From liquid to crystal via mechanochemical grinding: unique host-guest (HOF) cocrystal.

Mechanochemical synthesis via grinding of trimesic acid (TA, C9H6O6) and 4-chlorophenyl diphenyl phosphate (4CDP, C18H14ClO4P) (liquid at room temperature) in a 1:1 ratio resulted in the formation of an inclusion type of cocrystal. The crystallization of this phase via slow evaporation at low temperature (276-277 K) from methanol resulted in a rare `stairstep morphology' during the process of crystal growth. This morphology was not observed after crystallization of the compound from other solvents like toluene, dichloromethane, acetone, hexane and isooctane, and hence this was characteristically observed in methanol only. The characterization from single-crystal X-ray diffraction revealed the formation of a cocrystal with five molecules of TA and two molecules of 4CDP in the asymmetric unit. The trimesic acid molecules form hydrogen-bonded dimers resulting in hexagonal rings, and these rings are stacked through π-π intermolecular interactions to make a hexagonal honeycomb-like structure. The phosphate molecules, 4CDP, were found to be trapped as guests in these hexagonal channels. The similarity in the packing of trimesic acid is compared in the cocrystal and the free acid quantitatively via Xpac analysis, which establishes the relationship of a `2D supramolecular construct' between them. This signifies a unique type of arrangement in which the voids created by the trimesic acid moiety do not undergo distortion by the inclusion of the guest molecules. The quantitative analysis of the intermolecular interactions using Hirshfeld surfaces and fingerprint plots deciphers the role of both strong O-H...O hydrogen bonds and weak intermolecular interactions in the crystal packing.

Two-Dimensional Silver-Chalcogenolate-Based Cluster-Assembled Material: A p-type Semiconductor.

We have synthesized and characterized a new two-dimensional honeycomb architecture resembling a single-layer of atomically precise silver cluster-assembled material (CAM), [Ag12(StBu)6(CF3COO)6(4,4'-azopyridine)3] (Ag12-azo-bpy). The interlayer noncovalent van der Waals interactions within the single-crystals were successfully disrupted, leading to the creation of this unique structure. The optimized Ag12-azo-bpy CAM demonstrates a valence band that is localized on the Ag12 cluster node situated near the Fermi energy level. This localization induces electron injection from the linker to the cluster node, facilitating efficient charge transportation along the plane. Exploiting this single-layer structure as a distinctive platform for p-type channel material, it was employed in a field-effect transistor configuration. Remarkably, the transistor exhibits a high hole mobility of 1.215 cm2 V-1 s-1 and an impressive ON/OFF current ratio of ∼4500 at room-temperature.

Luminescent hexagonal microtubes prepared through water-induced self-assembly of a polymorphic organoboron compound: formation mechanism and waveguide behaviour.

Tetra-coordinated organoboron (TCOB) compounds are promising candidates for developing high-performance optical devices due to their excellent optoelectronic performance. Fabricating TCOB-based nanomaterials of controlled and defined morphology through rapid and easy-to-execute protocols can significantly accelerate their practical utility in the aforesaid applications. Herein, we report water-induced self-assembly (WISA) to convert a polymorphic TCOB complex (HNBI-B, derived from a 2-(2'-hydroxy-naphthyl)-benzimidazole precursor) into two unique nanomorphologies viz. nanodiscoids (NDs) and fluorescent microtubes with hexagonal cross-sections (HMTs). Detailed electron microscopic investigations revealed that oriented assembly and fusion of the initially formed NDs yield the blue emissive HMTs (SSQY = 26.7%) that exhibited highly promising photophysical behaviour. For example, the HMTs outperformed all the crystal polymorphs of HNBI-B obtained from CHCl3, EtOAc and MeOH in emissivity and also exhibited superior waveguide behaviour, with a much lower optical loss coefficient α' = 1.692 dB mm-1 compared to the rod-shaped microcrystals of HNBI-B obtained from MeOH (α' = 1.853 dB mm-1). Thus, this work reports rapid access to high performance optical nanomaterials through WISA, opening new avenues for creating useful nanomaterial morphologies with superior optical performance.

Quantitative evaluation of the electronic features involving "nucleophilic-electrophilic" character in the chalcogen sulfur.

This study investigates the crystal structures of substituted thiophenes and isothiocyanates by utilizing the method of in situ cryo-crystallization to gain quantitative insights into the electronic features of sulfur-centered interactions. This work reveals that the role of sulfur as a "nucleophilic" or "electrophilic" species during non-covalent interaction is significantly influenced by its immediate chemical and electronic surroundings.

Synthesis, biological evaluation, and computational investigation of ethyl 2,4,6-trisubstituted-1,4-dihydropyrimidine-5-carboxylates as potential larvicidal agents against Anopheles arabiensis.

Malaria is one of the most known vector-borne diseases caused by female Anopheles mosquito bites. According to WHO, about 247 million cases of malaria and 619,000 deaths were estimated worldwide in 2021, of which 95% of the cases and 96% of deaths occurred in the African region. Sadly, about 80% of all malaria deaths were of children under five years old. Despite the availability of different insecticides used to control this disease, the emergence of drug-resistant mosquitoes threatens public health. This, in turn, highlighted the need for new larvicidal agents that are effective at different larval life stages. This study aimed to identify novel larvicidal agents. To this end, a series of ethyl 2,4,6-trisubstituted-1,4-dihydropyrimidine-5-carboxylates 8a-i was synthesized using a three-step chemical synthetic approach via a Biginelli reaction employed as a key step. All title compounds were screened against Anopheles arabiensis to determine their larvicidal activities. Among them, two derivatives, ethyl 2-((4-bromophenyl)amino)-4-(4-fluorophenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate 8b and ethyl 2-((4-bromo-2-cyanophenyl)amino)-4-(4-fluorophenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate 8f, showed the highest larvicidal activity, with mortality of 94% and 91%, respectively, and emerged as potential larvicidal agents. In addition, computational studies, including molecular docking and molecular dynamics simulations, were carried out to investigate their mechanism of action. The computational results showed that acetylcholinesterase appears to be a plausible molecular target for their larvicidal property.Communicated by Ramaswamy H. Sarma.

Yoga and pain: A mind-body complex system.

Introduction: The human body's response to pain is indicative of a complex adaptive system. Therapeutic yoga potentially represents a similar complex adaptive system that could interact with the pain response system with unique benefits. Objectives: To determine the viability of yoga as a therapy for pain and whether pain responses and/or yoga practice should be considered complex adaptive systems. Methods: Examination through 3 different approaches, including a narrative overview of the evidence on pain responses, yoga, and complex system, followed by a network analysis of associated keywords, followed by a mapping of the functional components of complex systems, pain response, and yoga. Results: The narrative overview provided extensive evidence of the unique efficacy of yoga as a pain therapy, as well as articulating the relevance of applying complex systems perspectives to pain and yoga interventions. The network analysis demonstrated patterns connecting pain and yoga, while complex systems topics were the most extensively connected to the studies as a whole. Conclusion: All three approaches support considering yoga a complex adaptive system that exhibits unique benefits as a pain management system. These findings have implications for treating chronic, pervasive pain with behavioral medicine as a systemic intervention. Approaching yoga as complex system suggests the need for research of mind-body topics that focuses on long-term systemic changes rather than short-term isolated effects.

The deeper it goes, the brighter it glows: NIR emissive nitro-terrylene diimides with deep LUMOs.

Herein, we present the first examples of air-stable, deep-lowest unoccupied molecular orbital (LUMO) polycyclic aromatic molecules with emission in the near-infrared (NIR) region, using nitration as a strategy. Despite the fact that nitroaromatics are non-emissive, the choice of a comparatively electron-rich terrylene core proved to be beneficial for achieving fluorescence in these molecules. The extent of nitration proportionately stabilized the LUMOs. Tetra-nitrated terrylene diimide exhibited a deep-LUMO (≤-4.5 eV) of -5.0 eV vs. Fc/Fc+, the lowest for any larger RDIs. These are also the only examples of emissive nitro-RDIs, with larger quantum yields.

Characterization of non-covalent contacts in mono- and di-halo substituted acetaldehydes: probing the substitution effects of electron donating and withdrawing groups.

In the current work, a systematic evaluation of the different types of non-covalent interactions (NCIs) in acetaldehyde dimers, including dimers of mono-halo (XCH2CHO)2, di-halo (X2CHCHO)2 and tri-halo substituted (X3CCHO)2 acetaldehydes via the associated stabilization energy of these dimers has been performed. Furthermore, a topological analysis of the electron density based on the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction reduced density gradient (NCI-RDG) isosurfaces has also been performed to evaluate the nature of these NCIs. The geometrical and electronic characteristics have been evaluated via the presence of different electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) or substituents in dimers of these molecules, namely, XCH(Y)CHO and X2C(Y)CHO (wherein X = -F, -Cl, and -Br and Y = -SO3H, -CN, -NO2, -NH2, -CH3, -OCH3, and -SMe3). The C-H⋯O, C-H⋯X, X⋯X, X⋯O and C⋯O tetrel bonded contacts have been recognized to play an important role in the stabilization of the formed dimers. This study also establishes the fact that the overall stability of the dimeric assemblies is governed by the contributions from the mutual and complex interplay of a variety of interactions in the investigated dimers. Hence considerations based on strong H-bond donor-acceptor characteristics hold relevance for simple systems only, but slight alteration in the electronic environment can affect the overall stabilization energies of the system being investigated and the nature of the interactions that contribute towards the same.

Plastic Deformation in a Molecular Crystal Enables a Piezoresistive Response.

Organic materials are promising candidates for the development of efficient sensors for many medicinal and materials science applications. Single crystals of a small molecule, 4-trifluoromethyl phenyl isothiocyanate (4CFNCS), exhibit plastic deformation when bent, twisted, or coiled. Synchrotron micro-focus X-ray diffraction mapping of the bent region of the crystal confirms the mechanism of deformation. The crystals are incorporated into a flexible piezoresistive sensor using a composite constituting PEDOT: PSS/4CFNCS, which shows an impressive performance at high-pressure ranges (sensitivity 0.08 kPa-1 above 44 kPa).

Nitrate and Nitrite Reductions at Copper(II) Sites: Role of Noncovalent Interactions from Second-Coordination-Sphere.

Reductions of nitrate and nitrite (NOx-) are of prime importance in combatting water pollution arising from the excessive use of N-rich fertilizers. While examples of NOx- reductions are known, this report illustrates hydrazine (N2H4)-mediated transformations of NOx- to nitric oxide (NO)/nitrous oxide (N2O). For nitrate reduction to NO, initial coordination of the weakly coordinating NO3- anion at [(mC)CuII]2+ cryptate has been demonstrated to play a crucial role. A set of complementary analyses (X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR), UV-vis, and NMR spectroscopies) on NO3--bound metal-cryptates [(mC)MII(NO3)](ClO4) (1-M, M = Cu/Zn) demonstrates the binding of NO3- through noncovalent (NH···O, CH···O, and anion···π) and metal-ligand coordinate interactions. Subsequently, reactions of [(mC)CuII(14/15NO3)](ClO4) (1-Cu or 1-Cu/15N) with N2H4·H2O have been illustrated to reduce 14/15NO3- to 14/15NO. Intriguingly, in the absence of the second-coordination-sphere interactions, a closely related coordination motif [(Bz3Tren)CuII]2+ (in 3-Cu) does not bind NO3- and is unable to assist in N2H4·H2O-mediated NO3- reduction. In contrast, nitrite coordinates at the tripodal CuII sites in both [(mC)CuII]2+ and [(Bz3Tren)CuII]2+ irrespective of the additional noncovalent interactions, and hence, the N2H4 reactions of the copper(II)-nitrite complexes [(mC)CuII(O14/15NO)]+ and [(Bz3Tren)CuII(O14/15NO)]+ (in 2-Cu/4-Cu) result in a mixture of 14/15NO and N14/15NO.

Quantitative insights into noncovalent interactions involving halogen and tetrel bonds in 2,4,6-trimethylpyrylium tetrafluoroborate.

The crystal and molecular structure of an organic salt, in which a 2,4,6-trimethylpyrylium cation forms a salt with a tetrafluoroborate anion, namely, 2,4,6-trimethylpyrylium tetrafluoroborate, C8H11O+·BF4-, has been experimentally realized. The compound crystallizes in the orthorhombic centrosymmetric space group Pnma. The crystal packing is stabilized via a subtle interplay of [F3-B-F]-...O+-C fluorine/oxygen-centred halogen/chalcogen bonds and Cδ+...Fδ- tetrel-bonded contacts. Although the O centre has a formal charge of +1, the estimation of the partial negative charges on O is in accordance with electronegativity considerations. Hirshfeld surface analysis, which also includes an analysis of the three-dimensional deformation density, along with molecular electrostatic potential (MESP) calculations, provides quantitative insights into the nature of the intermolecular interactions. The topological analysis of the electron-density distribution has been performed using AIMAll and TOPOND, and unequivocally establishes the bonding character associated with the different noncovalent interactions. In addition, NBO analysis and polarizability calculations using PolaBer render deeper physical insights into the electronic characteristics of these noncovalent interactions.

Ultrasensitive colorimetric detection of fluoride and arsenate in water and mammalian cells using recyclable metal oxacalixarene probe: a lateral flow assay.

Globally 3 billion people are consuming water with moderately high concentrations of fluoride and arsenic. The development of a simple point of care (PoC) device or home device for the detection of fluoride/arsenic ensures safety before consuming water. Till date, lateral flow assay (LFA) based PoC devices can detect nucleic acids, viruses and diseases. An aluminium complex of rhodamine B functionalized oxacalix[4]arene (L) was designed to execute the LFA-based PoC device. Initially, Al3+ and Fe3+ ions were involved in complexation with the rhodamine B functionalized oxacalix[4]arene (L), resulting C1 (L-Al3+) and C2 (L-Fe3+) complexes respectively. The receptor L, as well as the probes (C1, C2), were characterized thoroughly using mass spectroscopy, FTIR, NMR, and EA. C1 and C2 were further utilized as recyclable probes for the detection of aqueous fluoride (21 ppb) and arsenate (1.92 ppb) respectively. The computational calculation indicates that upon complexation, the spirolactam ring opening at the rhodamine B site leads to optoelectronic changes. The consistency of LFA-based portable sensing device has been tested with water samples, synthetic fluoride standards and dental care products like toothpaste and mouthwash with concentrations ≥ 3 ppm. Moreover, fixed cell imaging experiments were performed to ascertain the in-vitro sensing phenomena.

AIEgens Based on Anion-π+ Interactions: Design, Synthesis, Photophysical Properties, and Their Applications in Material Science and Biology.

The design of novel aggregation-induced emission luminogens (AIEgens), has generally been facilitated by disrupting the possibility of π-π stacking. The recent literature describes a novel strategy to design AIEgens by introducing anion-π+ interactions to prevent the detrimental π-π stacking. This new strategy provides access to intrinsically charged AIEgens whose photophysical properties can be tuned either by incorporating different substituents on the π-molecular scaffold to modulate the acidity for tuning the interaction energy between a π-acceptor and counter-anions. This concept article provides a brief overview of the field, focusing on the synthesis of AIEgens, their photophysical properties, crystallography studies and their applications in live cell fluorescence imaging.

Current Approaches to Yoga in U.S. Medical Schools: Scoping Review of the Literature.

Background: Yoga is described as a system of physical and mental practices originating from India that connects mind, body, and spirit with techniques such as physical exercises, breathing, and meditation to promote health and well-being. Medical students experience an immense amount of stress that unfortunately continues throughout their residency and careers. Yoga represents a tool to reduce stress and support medical student resilience. Objective: This study aims to evaluate the current approaches to yoga in U.S. medical schools. Methods: A scoping literature review was conducted using search terms such as "medical school," "medical student," "medical education," "yoga," "asana," "pranayama," and "mindfulness." The primary aim of the review was to examine if U.S. medical schools offer accessible yoga to medical students and the characteristics of those yoga programs. Results: The search yielded 1313 primary articles. All titles and abstracts were screened for eligibility. Duplicate articles were removed, and 156 articles were reviewed independently by two authors. A total of eight articles met all the criteria. Yoga is offered in medical schools through three main models: recreational, research, and educational. All of the studies indicated various positive effects on medical students from these yoga programs, including in psychological states, perceived stress, and scores on medical knowledge assessments. Conclusions: Yoga aligns well with the objectives of medical education by combining physician resiliency, mindfulness, and education that can ultimately serve patients. Greater opportunities should be created to engage medical students in yoga through the length of their entire undergraduate and graduate medical training.