Reversible and Reproducible Hydrogen Storage in Single- Walled Carbon Nanotubes Functionalized with Borane

In this chapter, commercial single-walled carbon nanotubes (SWCNTs) were purified by standard methods and functionalized with borane (BH3). The morphology, presence of elements and vibrations of different functional groups are probed by transmission electron microscopy (TEM), energy dispersive (ED) spectroscopy, and Fourier transform infrared spectroscopy (FTIR), respectively. A Sievert-like hydrogenation setup has been designed and is employed for hydrogenating the functionalized SWCNTs for different time durations. The amount of hydrogen stored in the functionalized SWCNTs has been quantified using elemental analysis, carbon, hydrogen, nitrogen, sulfur (CHNS) combined with thermal (TG/TDS) measurements. A maximum of 4.77 wt.% of hydrogen has been stored at 50°C and the samples become dehydrogenated in the temperature range 90–125°C. From the experiments, it has been found that the amount of hydrogen stored in functionalized SWCNTs increases with increasing hydrogenation duration. Moreover, the entire hydrogenation and dehydrogenation process was examined by Raman, thermal, and elemental analyses together. During the experiments, hydrogenation and dehydrogenation processes were stabilized and were found to be repeatable. Overall, the achieved hydrogen storage capacity of SWCNTS functionalized with BH3 is close to the US DOE target

Aggregation behavior in naphthalene-appended diketopyrrolopyrrole derivatives and its gas adsorption impact on surface potential

Diketopyrrolopyrrole derivatives containing phenyl and thiophene units adorned with alkoxynaphthalene (Naph-PDPP and Naph-TDPP) were synthesized by a Suzuki cross-coupling reaction. The effect of the phenyl/thiophene units on the aggregation behavior and detailed photophysical properties were investigated by UV-visible, steady-state, and time-resolved fluorescence spectroscopy. The absorption and fluorescence spectra of Naph-PDPP and Naph-TDPP in the solid-state exhibit red-shifted spectral patterns due to strong intermolecular interactions. The concentration-dependent photophysical properties reveal the formation of J-type aggregates at higher concentrations and in the solid state. The extent of aggregate formation is higher for Naph-TDPP. DFT and TD-DFT studies showed that Naph-TDPP containing a thiophene ring in the backbone adopts a more planar geometry than Naph-PDPP and undergoes strong pi-pi stacking interactions that favor the formation of J-aggregates. Scanning Kelvin probe measurements on the thin films of Naph-PDPP and Naph-TDPP were performed (both in the dark and under visible light) upon exposure to different volatile organic vapors (ethanol and triethylamine). The study reveals that under visible light illumination, the Naph-PDPP thin film has significant gas adsorption towards ethanol vapors and alters its sign of response

Development of Gas Sensor Array based on Phthalocyanines Functionalized TiO₂/ZnO Heterojunction Thin Films

Gas sensing properties of diverse phthalocyanines functionalized TiO2/ZnO heterojunction thin films were investigated respect to a number of volatile organic compounds (VOCs) in both dark and light conditions. These studies showed that influence of heterojunction along with functionalization alter the optical properties and gas sensing of sensors. Results show that each sensor exhibits a different pattern of relative sensitivity, and this feature can be used to discriminate among a wide range of VOCs

Influence of gas adsorption on surface potential of porphyrin functionalized boron doped diamond thin films

Porphyrins functionalized diamond surfaces are interesting candidates for wide variety of applications due to their remarkable physical and chemical properties. In this work, the properties of 5-(4-carboxyphenyl) triphenyl porphyrins functionalized boron-doped diamond (BDD) surface followed by gas adsorption were studied at room temperature. After structural and morphological characterizations of the bare BDD surface and porphyrins functionalized BDD surface, a scanning Kelvin probe system was used to investigate the surface potential distribution due to the adsorption of volatile organic compounds (VOCs) under visible light illumination conditions. Gas adsorption studies showed poor response in bare BDD surfaces under different gas atmospheres. On the other hand, a significant response with discriminable gas interactions was achieved in porphyrins functionalized BDD surface under visible light illumination. The obtained results suggest that visible light has influenced gas interactions because of porphyrins. The increased response (~ 2.5 times) of metal-free porphyrin functionalized BDD thin film towards triethylamine (TEA) is accounted to the donor nature of TEA. This study helps in developing a new generation of novel conductive type diamond-based photo enhanced gas sensors at room temperature that can be utilized for fish freshness monitoring

A ZIF-67 derived Co 3 O 4 dodecahedron shaped microparticle electrode based extended gate field-effect transistor for non-enzymatic glucose detection towards the diagnosis of diabetes mellitus

The present study focuses on non-enzymatic glucose detection using an extended gate field-effect transistor (EGFET) based on zeolitic imidazole framework-67 (ZIF-67) derived cobalt tetraoxide (Co3O4) dodecahedron shaped microparticles. XRD has confirmed the cubic phase of Co3O4. HR-SEM images have highlighted hollow Co3O4 dodecahedra with an average particle size of 1.72 mu m. A cost-effective single-use ZIF-67 derived Co3O4 electrode has been fabricated that covers the range of glucose concentration from 1.5 mM to 42 mM (linear range: 1.5 to 10.5 mM) and has a fast response time of <4 s. The sensitivity is calculated to be 50 mu A mM(-1) cm(-2). Our prepared electrode has demonstrated a good selective response against other interfering molecules like sucrose, lactose, fructose, uric acid, and ascorbic acid. The concentration of the interfering molecules is maintained similar to the physiological conditions of human blood. As a maiden attempt, the influence of glucose concentration on the surface potential of the sensing electrode has been investigated using a scanning Kelvin probe (SKP). We have found that the work function decreases with the increase of glucose concentration. Overall, EGFET and SKP studies have revealed that the ZIF-67 derived Co3O4 dodecahedron shaped microparticle based electrode is suitable for rapid detection of glucose

A self-powered photoactive room temperature gas sensor based on a porphyrin-functionalized ZnO nanorod/p-Si heterostructure

The integration of self-powered photodetectors and highly selective gas sensors into a unified system has revolutionized the development of next-generation optoelectronic gas sensors towards overcoming the limitations of high power consumption and poor selectivity in traditional systems. In this scenario, this work describes a superior optoelectronic gas sensor based on 5-(4-carboxyphenyl)-10,15,20-triphenyl porphyrin (H2TPPCOOH)-functionalized vertically aligned 1D ZnO nanorods grown on p-Si. The dual impact of porphyrin functionalization on the powering and chemical sensing properties of the ZnO NR/p-Si heterostructure was investigated. The resulting porphyrin-functionalized device demonstrated a maximum VOC of 0.1 V and Isc of 12.16 mu A with good sensitivity and fast response towards triethylamine (TEA) vapors at room temperature. The level of defects in the device and the gas sensing mechanism were studied using the Scanning Kelvin Probe system, and the photoelectric mechanism is explained through energy band diagrams. The ambipolar charge transport in the device plays a significant role in chemical sensing at room temperature at zero power consumption. Hence, this work offers valuable insights for designing self-sustained, stable, cost-effective, miniaturized smart chemical sensors, which are highly selective to specific VOC biomarkers in complex gas mixtures, with a potential for on-chip integration and point-of-care health monitoring.The integration of self-powered detectors and selective gas sensors into a single system introduces a next-generation of optoelectronic gas sensors that overcome the limitations of power consumption and poor selectivity

Self-Powered Photodetectors with Nickel-Doped ZnO Nanorods for Operation in Low-Light Environments

The development of next-generation optoelectronic devices relies on the necessity for self-powered, fast, and high-sensitivity photodetectors with a wide-spectral response. This Article investigates the impact of nickel doping on the growth of ZnO nanorods (79–123 nm diameter) on a p-type silicon substrate, exploring alterations in photovoltaic characteristics compared to the pure counterparts. The results reveal enhanced performances in devices with nickel doping ranging from 1% to 5%, exhibiting superior behavior across tested parameters. Despite consistent morphology and geometric aspects of the grown nanorods, the persistent presence of nickel was evident. Illumination from UV and visible light sources demonstrated increased current in I–V plots with rising doping levels, showcasing robust photovoltaic behavior at 0 V and enabling functionality as a self-powered photodetector. Under UV light, self-powered operation was observed at an intensity as low as 20 mW/cm2, extending beyond 50 mW/cm2 for visible light exposure. These devices exhibit applicability in detecting a broad spectrum of solar radiation, as evidenced by the influence of the wavelength and light intensity on the photocurrent response at zero bias. With pulsed frequencies of a 405 nm laser, changes in the photocurrent were observed with variations in operating frequency. Hence, a high-performance, wide spectral, self-powered photodetector capable of detecting minimal light intensity was fabricated