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In this study, we investigated a surface acoustic wave (SAW) sensor based on noble metal palladium-modified reduced graphene oxide (Pd-rGO) for the detection of a low concentration of NO2 gas at room temperature. A spin-coating technique was used to deposit Pd-rGO films onto an ST-cut quartz substrate. The SEM and Brunauer-Emmett–Teller (BET) characterization results indicate that the Pd-rGO composite film possesses large specific surface areas and provides sufficient adsorption active sites for NO2 gas. The experimental results showed that the prepared Pd-rGO SAW sensor had an enhanced gas-sensing performance to the NO2 gas (1–50 ppm) with high sensitivity (146.9 Hz/ppm), lower limit of detection (LOD, ~1 ppm), and excellent long-term stability, which can be attributed to the dissociation catalytic ability of the noble metal Pd. Meanwhile, compared to interfering gases such as CO, C6H6, C2H5OH, HCl, and H2S, the SAW sensor with Pd-rGO film exhibited a good selectivity toward NO2. These results identified the potential value of the Pd-rGO composite in the field of gas sensing, and it holds great promise in the realm of environmental protection.

Alternaria alternataand Phytophthora nicotianaeare two major necrotrophic pathogens of tobacco. It is currently unknown whether they elicit the same suite of defense responses and whether jasmonate (JA) signaling plays an important role in the defense response of cultivated tobacco against these two pathogens. During transcriptome analysis, we found some conserved defense responses in the flue‐cured tobacco cultivar K326 against A. alternataand P. nicotianae. Of the top 20 significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways, eight were shared in ‘K326’ plants inoculated with A. alternataor P. nicotianae; these included the phenylpropanoid biosynthesis and the sesquiterpenoid biosynthesis pathways. Induction of expression of the genes feruloyl‐CoA 6′‐hydroxylase 1(F6’H1), 5‐epi‐aristolochene synthase(EAS), and 5‐epi‐aristolochene hydroxylase(EAH) for biosynthesis of the phytoalexins scopoletin (F6’H1) and capsidiol (EASand EAH) was further confirmed by real‐time polymerase chain reaction, and they are representative genes of phenylpropanoid and sesquiterpenoid pathways. Further analysis showed that the levels of JA and JA‐Ile, and transcripts of allene oxide cyclase(AOC), the key enzyme gene for JA biosynthesis, were also significantly induced by both pathogens in ‘K326.’ Plants silenced for either AOCor Coronatine Insensitive 1(COI1), the gene encoding the JA‐Ile receptor, were highly susceptible to infection by both pathogens. Taken together, our results show that defense responses, especially the activation of the pathways for biosynthesis of the phytoalexins scopoletin and capsidiol, are conserved in N. attenuataand cultivated tobacco infected by A. alternataand P. nicotianae, and provided compelling evidence for the role of JA signaling in the defense against these two pathogens. Shared pathways are enriched in transcriptome in cultivated tobacco after A. alternataand P. nicotianaeinoculation.Jasmonate as a conserved signaling is elicited in cultivated tobacco after A. alternataor P. nicotianaeinoculation.Plants silenced with AOCor COI1were highly susceptible to A. alternataand P. nicotianae.

Efficient, high-power, and widely tunable Tm-doped fiber lasers cladding-pumped by diode lasers at 791 nm are demonstrated by use of an external cavity containing a diffraction grating. A maximum output power of 62 W is obtained at 2 004 nm for 140 W of launched pump power, corresponding to a slope efficiency of 48% with respect to launched pump power. The operating wavelength is tunable over 200 nm (1 895 to 2 109 nm), with >52 W of output power over a tuning range of 140 nm (1 926 to 2 070 nm). Prospects for further improvement in output power, lasing efficiency, and tuning range are considered.