Molybdenum disulfide (MoS₂) and nanocrystalline diamond (NCD) have attracted considerable attention due to their unique electronic structure and extraordinary physical and chemical properties in many applications, including sensor devices in gas sensing applications. Combining MoS₂ and H-terminated NCD (H-NCD) in a heterostructure design can improve the sensing performance due to their mutual advantages. In this study, the synthesis of MoS₂ and H-NCD thin films using appropriate physical/chemical deposition methods and their analysis in terms of gas sensing properties in their individual and combined forms are demonstrated. The sensitivity and time domain characteristics of the sensors were investigated for three gases: oxidizing NO₂, reducing NH₃, and neutral synthetic air. It was observed that the MoS₂/H-NCD heterostructure-based gas sensor exhibits improved sensitivity to oxidizing NO₂ (0.157%·ppm^-1) and reducing NH₃ (0.188%·ppm^-1) gases compared to pure active materials (pure MoS₂ achieves responses of 0.018%·ppm^-1 for NO₂ and -0.0072%·ppm^-1 for NH₃, respectively, and almost no response for pure H-NCD at room temperature). Different gas interaction model pathways were developed to describe the current flow mechanism through the sensing area with/without the heterostructure. The gas interaction model independently considers the influence of each material (chemisorption for MoS₂ and surface doping mechanism for H-NCD) as well as the current flow mechanism through the formed P-N heterojunction.

Nanostructured boron-doped diamond (BDD) offers a sizeable ion-accessible area, high mechanical robustness, and high electrical conductivity, and could be a suitable electrode for high-performance electrochemical (EC) supercapacitors. Herein, two morphological BDD films, namely, boron-doped microcrystalline diamond (BMCD) and boron-doped ultra-nanocrystalline diamond (BUNCD), are employed for nanostructuring. The diamond nanopillars are fabricated via the Au mask-assisted reactive ion etching (RIE) method. The nanostructured samples of BMCD and BUNCD are termed BMCD_N and BUNCD_N. The Raman spectroscopy and X-ray photoelectron spectroscopy measurements of these nanostructured samples confirm the presence of sp² in sp³-bonded carbon, which combine to offer good EC activity of sp² and exceptional stability of sp³ carbon. These nanostructured BDD samples with enhanced surface area are utilized as electrode materials to construct an electric double-layer capacitor and pseudocapacitor. In 1 M Na₂SO₄ solution, the maximum specific capacitance of BMCD_N is found to be 0.0852 mF cm⁻², whereas, for BUNCD_N the value is 0.0784 mF cm⁻². The electrochemical analysis of these samples shows they exhibit superior electron transfer kinetics with 80% capacitance retention after 2000 cycles, which indicates the suitable utilization of these nanostructured samples as electrodes in EC supercapacitors.

The miniaturization of electrochemical supercapacitors (EC‐SCs) requires electrode materials that are both durable and efficient. Boron‐doped diamond (BDD) films are an ideal choice for EC‐SC due to their durability and exceptional electrochemical performance. In this study, nanostructured boron‐doped ultra‐nanocrystalline diamonds (NBUNCD) are fabricated on Si micro‐pyramids (Si _P ) using a simple reactive ion etching (RIE) process. During the etching process, the high aspect ratio and the induction of sp ² graphite in these nanorod electrodes achieved a maximum specific capacitance of 53.7 mF cm ⁻² at a current density of 2.54 mA cm ⁻² , with a 95.5% retention after 5000 cycles. Additionally, the energy density reached 54.06 µW h cm ⁻² at a power density of 0.25 µW cm ⁻² . A symmetric pouch cell using NBUNCD/Si _P exhibited a specific capacitance of 0.23 mF cm ⁻² at 20 µA cm ⁻² , an energy density of 31.98 µW h cm ⁻² , and a power density of 0.91 µW cm ⁻² . These superior EC properties highlight NBUNCD/Si _P ’s potential for advancing miniaturized supercapacitors with high capacitance retention, cycle stability, and energy density.

A nanocrystalline diamond (NCD) layer is used as an active (sensing) part of a conductivity gas sensor. The properties of the sensor with an NCD with H-termination (response and time characteristic of resistance change) are measured by the same equipment with a similar setup and compared with commercial sensors, a conductivity sensor with a metal oxide (MO_X) active material (resistance change), and an infrared pyroelectric sensor (output voltage change) in this study. The deposited layer structure is characterized and analyzed by Scanning Electron Microscopy (SEM) and Raman spectroscopy. Electrical properties (resistance change for conductivity sensors and output voltage change for the IR pyroelectric sensor) are examined for two types of gases, oxidizing (NO₂) and reducing (NH₃). The parameters of the tested sensors are compared and critically evaluated. Subsequently, differences in the gas sensing principles of these conductivity sensors, namely H-terminated NCD and SnO₂, are described.