Efficient Heterostructures of Ag@CuO/BaTiO₃ for Low-Temperature CO₂ Gas Detection: Assessing the Role of Nanointerfaces during Sensing by Operando DRIFTS Technique

Tetragonal BaTiO₃ spheroids synthesized by a facile hydrothermal route using Tween 80 were observed to be polydispersed with a diameter in the range of ∼15–75 nm. Thereon, BaTiO₃ spheroids were decorated with different percentages of Ag@CuO by wet impregnation, and their affinity toward carbon dioxide (CO₂) gas when employed as sensitive layers in a microsensor was investigated. The results revealed that the metal nanocomposite-based sensor had an exceptional stability and sensitivity toward CO₂ gas (6-fold higher response), with appreciable response and recovery times (<10 s) and higher repeatability (98%) and accuracy (96%) at a low operating temperature of 120 °C, compared to those of pure BaTiO₃ and CuO. Such improved gas-sensing performances even at a very low concentration (∼700 ppm) is attributable to both the chemical and electrical contributions of Ag@CuO forming intermittent nanointerfaces with BaTiO₃ spheroids, exhibiting unique structural stability. The CO₂-sensing mechanism of CuO/BaTiO₃ nanocomposite was studied by the diffuse reflectance infrared Fourier transform spectroscopy technique that established the reaction of CO₂ with BaO and CuO to form the respective carbonate species that is correlated with the change in material resistance consequently monitored as sensor response

Highly Selective CO₂ Gas Sensing Properties of CaO-BaTiO₃ Heterostructures Effectuated through Discretely Created <i>n‑n</i> Nanointerfaces

Globally recognized for its role as an occupational hazard, carbon dioxide (CO₂) detection and monitoring is essential in agriculture, chemical manufacturing, and healthcare/clinical-oriented applications. Although, optical and chemical gas sensors are available commercially, current gas sensing technologies involving selective monitoring of CO₂ at lower detection limits specifically for industrial conditions still remains a formidable challenge. Herein, we present a simple strategy for highly selective CO₂ detection using an inexpensive transducer platform based on reversible chemisorbed carbonation between CO₂ and CaO-BaTiO₃ heterostructures. Microsensors showed an optimum sensitivity of 65% toward 1000 ppm of CO₂ gas and superior selectivity when operated at 160 °C. Such a remarkable sensing performance originates from the discretely created <i>n-n</i> nanointerfaces and conveniently actualized staggered energy band positions that promote favorable charge transfer upon exposure to CO₂ gas molecules even at parts per million levels. Reversible sensing phenomenon is demonstrated using <i>operando</i> time-resolved diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and correlated with energy band alignment determined from the ultraviolet diffuse reflectance (UV-DRS) spectra to propose the sensing mechanism

Once daily baclofen sustained release or gastro-retentive system are acceptable alternatives to thrice daily baclofen immediate release at same daily dosage in patients

Background: Baclofen, a GABA-agonist, is currently available as an immediate release (IR) formulation for relieving neurogenic spasticity in a variety of disorders. Baclofen IR requires to be administered three times a day which inadvertently increases the chances of medication noncompliance among patients and is also associated with side effects such as drowsiness and muscle weakness. Aim: To overcome the shortcomings of baclofen IR, two modified formulations, baclofen sustained release (SR) and gastric retentive system (GRS), have been proposed to be equivalent in efficacy to baclofen IR with the administration of a single daily dose. Materials and Methods: Ninety patients with chronic neurogenic muscular spasticity were enrolled requiring 10-20 mg of baclofen IR every eight hours. The patients were randomized to two treatment arms: SR (n = 46) or GRS (n = 44) at the same once-daily dose for four weeks. Efficacy was measured by Ashworth score for muscle tone, spasm score, reflex score, 30-item functional independence score, and patient′s diary score for three most affected activities of daily life. Results: The mean Ashworth score changed significantly (P = 0.00) for patients in the SR group from 3.03-2.69 (-0.35) and 3.07-2.70 (-0.37) for patients in the GRS group. There was no significant difference (P = 0.87) between baseline-adjusted Ashworth score reductions on SR (-0.35) and GRS (-0.37). Similar results were obtained for spasm, reflex, and functional independence scores. The mean baseline-adjusted patient-diary scores did not differ significantly between 8 am, 12 pm, 4 pm, and 8 pm (P = 0.96), either on SR (-5.3 to -6.1) or GRS (-7.3 to -8.1), indicating a uniform effect round-the-day on both. Further, sedation scores (mean ± SEM) decreased significantly (P < 0.05) on both SR (10.36 ± 1.37 to 6.18 ± 0.92) and GRS (8.14 ± 1.57 to 5.33 ± 1.11), suggesting better toleration. Conclusion: Once-daily baclofen SR and GRS are efficacious, convenient, and better-tolerated alternatives to baclofen IR in patients with neurogenic spasticity

Straddled Band Aligned CuO/BaTiO₃ Heterostructures: Role of Energetics at Nanointerface in Improving Photocatalytic and CO₂ Sensing Performance

This work details novel insights on the role of energetics, that is, energy band bending and built-in potential at the nanointerface of CuO/BaTiO₃ forming type I <i>p</i>/<i>n</i> heterostructures, evaluated by correlating X-ray photoelectron spectroscopy and ultraviolet diffuse reflectance spectroscopy studies. Cetyltrimethyl­ammonium bromide (CTAB) assisted hydrothermal route was used to synthesize BaTiO₃ cuboids with six active {100} facets, and its CuO based heterostructures were tested for bifunctional applications in environmental nanoremediation. Straddled CuO/BaTiO₃ heterostructures reported herein showcased exceptional flexibility as a ultraviolet (UV) active photocatalyst for methyl orange (MO) degradation and chemo-resistive CO₂ gas sensor. CuO/BaTiO₃ heterostructures in equimole ratio could degrade 99% MO in 50 min with rate constant (κ) of a first-order reaction observed to be 10 and 100-fold greater in comparison with BaTiO₃ and CuO samples, respectively. Subsequently, in a parallel application, trials were carried out on CuO/BaTiO₃ heterostructures for their sensitivity and stability toward CO₂ gas below 5000 ppm. Upon Ag decoration, the sensor response improved compared to CuO/BaTiO₃ heterostructures at 160 °C, with enhanced response/recovery times (<i>t</i>₉₀) of 300 and 320 s, respectively towards 100 ppm CO₂ gas. Improved photoactivity was rationalized in terms of effective charge severance of photogenerated e–h pairs owing to favorable band alignment, while the optimum CO₂ sensor response was attributed to efficient nanointerfaces configured in large numbers and Ag⁰/Ag⁺ acting as redox couple