We report n-type conductivity in phosphorus ion implanted ultrananocrystalline diamond films annealed at 800 °C and above. The amorphous carbon transits to diamond with an increase of stress after 900 °C annealing, which exhibits lower resistivity with Hall mobility of 143 cm2/Vs. After 1000 °C annealing, the diamond transits to amorphous carbon with the stress release, which has higher carrier concentration and lower Hall mobility. Both P+-implanted nano-sized diamond grains and amorphous carbon give contributions to the n-type conductivity in the films. The microstructure evolution and electrical properties are relative to the hydrogen diffusion and desorption under high temperature annealing.

Ultrananocrystalline diamond (UNCD) films were implanted by oxygen ion and annealed at different temperatures. The electrical and structrual properties of O+-implanted UNCD films were investigated by Hall effects, high-resolution transmission electron microscopy (HRTEM) and uv Raman spectroscopy measurements. The results show that O+-implanted nano-sized diamond grains annealed at 800 °C and above give n-type conductivity to the sample and the UNCD film exhibits n-type resistivity with the carrier mobility of 1∼11 cm2 V−1s−1. With O+ dose increasing from 1015 to 1016 cm−2, diamond phase transits to the amorphous carbon phase accompanied by n-type semiconduction transforming to metallic conduction. In the 1014 cm−2 O+-implanted UNCD film, some amorphous carbon at grain boundaries transits to diamond phase with annealing temperature (Ta) increasing from 500 °C to 800–900 °C, and some of diamond grains are found to be converted to amorphous carbon phase again after 1000 °C annealing. This phase transition is closely relative to the n-type conductivity of the UNCD films, in which n-type conductivity increases with the amorphous carbon phase transiting to diamond phase in the Ta range of 500–900 °C, and it decreases with diamond phase transiting to amorphous carbon phase in the case of 1000 °C annealing. It is indicated that the O+-implanted nano-sized diamond grains dominantly control the n-type conductivity of UNCD film in the Ta range of 800–900 °C, while the grain-boundary-conduction controls the n-type conductivty in UNCD film annealed at 1000 °C. In this case, a novel conduction mechanism that O+-implanted nano-sized diamond grains supply n-type conductivity and the amorphous carbon grain boundaries give a current path to the UNCD films is proposed.

Self‐assembled nanoparticle networks have emerged as multifunctional building blocks for a new generation of highly sensitive sensing technologies that offer large surface‐to‐volume ratios and a range of associated benefits. Unfortunately, with nanoparticle networks often being held together by weak van der Waals forces, the development of useful commercial devices is slowed by the relatively low robustness and poor carrier transport characteristics. This study shows how the application of a single droplet of ethanol can induce capillary forces capability of delivering significant changes to the morphological, structural, optical, and electronic properties of ZnO nanoclusters. It demonstrates how ZnO nanocluster “dendrites” and nanoparticles are forced together to form micro‐scale islands and larger nanoparticles, and thereby improve the robustness of the layers and the quality of the junctions between the nanoparticles without significantly reducing the overall porosity of the layer or degrading the structural or optical properties in any way. The commensurate improvement in the electronic transport within the layers is found to greatly improve the photoresponse of UV detectors. It seems likely that the application of ethanol and the exploitation of capillary force can provide a technique that can greatly benefit any nanostructured, ultra‐porous device where poor charge transport currently limits performance.

In the last decades, nanomaterials have emerged as multifunctional building blocks for the development of next generation sensing technologies for a wide range of industrial sectors including the food industry, environment monitoring, public security, and agricultural production. The use of advanced nanosensing technologies, particularly nanostructured metal-oxide gas sensors, is a promising technique for monitoring low concentrations of gases in complex gas mixtures. However, their poor conductivity and lack of selectivity at room temperature are key barriers to their practical implementation in real world applications. Here, we provide a review of the fundamental mechanisms that have been successfully implemented for reducing the operating temperature of nanostructured materials for low and room temperature gas sensing. The latest advances in the design of efficient architecture for the fabrication of highly performing nanostructured gas sensing technologies for environmental and health monitoring is reviewed in detail. This review is concluded by summarizing achievements and standing challenges with the aim to provide directions for future research in the design and development of low and room temperature nanostructured gas sensing technologies.

As an emerging class of hybrid nanoporous materials, metal-organic frameworks (MOFs) have attracted significant attention as promising multifunctional building blocks for the development of highly sensitive and selective gas sensors due to their unique properties, such as large surface area, highly diversified structures, functionalizable sites and specific adsorption affinities. Here, we provide a review of recent advances in the design and fabrication of MOF nanomaterials for the low-temperature detection of different gases for air quality and environmental monitoring applications. The impact of key structural parameters including surface morphologies, metal nodes, organic linkers and functional groups on the sensing performance of state-of-the-art sensing technologies are discussed. This review is concluded by summarising achievements and current challenges, providing a future perspective for the development of the next generation of MOF-based nanostructured materials for low-temperature detection of gas molecules in real-world environments.

The real-time detecting and monitoring of ethylene gas molecules could benefit the agricultural, horticultural and healthcare industries. In this regard, we comprehensively review the current state-of-the-art ethylene gas sensors and detecting technologies, covering from preconcentrator-equipped gas chromatographic systems, Fourier transform infrared technology, photonic crystal fiber-enhanced Raman spectroscopy, surface acoustic wave and photoacoustic sensors, printable optically colorimetric sensor arrays to a wide range of nanostructured chemiresistive gas sensors (including the potentiometric and amperometric-type FET-, CNT- and metal oxide-based sensors). The nanofabrication approaches, working conditions and sensing performance of these sensors/technologies are carefully discussed, and a possible roadmap for the development of ethylene detection in the near future is proposed.

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We report that the diffusion and desorption of hydrogen (H) play a key role in the diamond/amorphous carbon phase transitions of O+-implanted UNCD films at different annealing temperatures (Ta) by using high resolution transmission electronic microscopy (HRTEM), vis-uv Raman, and Fourier transform infrared (FTIR) spectroscopy measurements. The results of HRTEM and uv Raman spectroscopy measurements show that with Ta increasing from 500 to 900 °C, the amorphous carbon in grain boundaries (GBs) transits to diamond phase. Visible Raman spectroscopy measurements show that the amount of H bonded to trans-polyacetylene (TPA) chains in GBs reduces with Ta increasing to 900 °C, while that of H terminating to the surfaces of diamond grains increases confirmed by FTIR measurements. It reveals that H diffuses from GBs to the surfaces of diamond grains. In this process, the active H extracts H which terminates the diamond surface, leaving a reactive surface site. This gives a chance for the neighbored amorphous carbon clusters to attach to the surface site, so that diamond grains become larger. After 1000 °C annealing, the amount of diamond phase dramatically decreases and diamond transits to amorphous carbon by HRTEM and uv Raman spectroscopy. It is observed that the amount of H bonded to TPA chains in GBs and that of H terminating to the surfaces of diamond grains dramatically decreases from visible Raman spectroscopy and FTIR measurements. It is revealed that H is desorbed from both surfaces of diamond grains and GBs, which forces diamond grains to collapse to amorphous carbon