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A modification approach is developed based on the idea of molecular imprinting technique to enhance the selective gas sensing performance of nanostructured SnO2 as gas sensors. The modification procedure, conducted on SnO2 microspheres as the porous substrate, involves in situ polymerization and calcination processes. A methanol-templated molecularly imprinted sample (cM-SnO2 MIP) was successfully synthesized via the modification procedure, which demonstrated great difference with its nonmodified counterpart (c-SnO2 MSs) in terms of both surface morphology and internal architecture. Gas sensing performance, including target gas response, selectivity, and dynamic sensing behavior, was investigated to validate the effectiveness of the imprinted cavities for methanol within cM-SnO2 MIPs. Compared to c-SnO2 MSs, the cM-SnO2 MIPs exhibited greatly enhanced methanol sensing selectivity and improved anti-interference ability by up to 2–10 times depending on the types of interference gases. Moreover, the predesigned target gas recognition capability of the molecularly imprinted sensors was proved by changing the template to ethanol and thus obtaining cE-SnO2 MIPs with excellent ethanol sensing selectivity as well as improved anti-interference ability. By constructing a sensor array, the excellent sensing selectivity of these nanostructured SnO2 microspheres was exploited to distinguish the chemically similar molecules, methanol and ethanol. [ABSTRACT FROM AUTHOR]

Gold and Bi-bearing parageneses are pivotal to understanding gold concentration and deposition processes. The large-scale Laozuoshan gold deposit is located in the Jiamusi Block, northeastern China, and has experienced complex mineralization processes with abundant gold and Bi-bearing minerals. However, the relationship between Bi-minerals and gold is unclear, preventing our understanding of the gold enrichment and precipitation mechanism in the Laozuoshan gold deposit. Optical microscope and SEM results show three stages of gold mineralization: pyrrhotite (Po-1) + arsenopyrite (Apy-1) + Bi-bearing minerals (Bis-1) + Au-1; arsenopyrite (Apy-2) + chlorite + Bi-bearing minerals (Bis-2) + Au-2; and arsenopyrite (Apy-3) + graphite + Bi-bearing minerals (Bis-3) + Au-3. The abundant amount of gold (Au-1~Au-3) is associated with Bi-bearing minerals (Bis-1~Bis-3), which coexist as inclusions and fill in fractures in these minerals. The mineral assemblages of arsenopyrite, Bi-minerals, and gold exhibit a clear As-Bi-Au mineralogy in the ores, and the ternary diagram of the chemical compositions of the Bi-minerals shows that Bi-minerals all fall in reducing regions, indicating that Bi-minerals are precipitated under reducing conditions. The gold compositions demonstrate a positive correlation (R2 = 0.58) between Au and Bi. Consequently, we propose that the gold experienced the ore-forming fluids concentration and further Bi-melts scavenging for the Laozuoshan gold deposit mineralization. The Bi collector model is essential in interpreting the high-grade gold in the Laozuoshan gold deposit, indicating that the geochemical anomalies observed with bismuth may be a critical potential exploration target for the high-grade gold deposits in the Jiamusi Block. [ABSTRACT FROM AUTHOR]

The ginsenoside Rg3 found in Panax species has extensive pharmacological properties, in particular anti‐cancer effects. However, its natural yield in Panax plants is limited. Here, we report a multi‐modular strategy to improve yields of Rg3 in a Panax ginseng chassis, combining engineering of triterpene metabolism and overexpression of a lignin biosynthesis gene, phenylalanine ammonia lyase (PAL). We first performed semi‐rational design and site mutagenesis to improve the enzymatic efficiency of Pq3‐O‐UGT2, a glycosyltransferase that directly catalyzes the biosynthesis of Rg3 from Rh2. Next, we used clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) gene editing to knock down the branch pathway of protopanaxatriol‐type ginsenoside biosynthesis to enhance the metabolic flux of the protopanaxadiol‐type ginsenoside Rg3. Overexpression of PAL accelerated the formation of the xylem structure, significantly improving ginsenoside Rg3 accumulation (to 6.19‐fold higher than in the control). We combined overexpression of the ginsenoside aglycon synthetic genes squalene epoxidase, Pq3‐O‐UGT2, and PAL with CRISPR/Cas9‐based knockdown of CYP716A53v2 to improve ginsenoside Rg3 accumulation. Finally, we produced ginsenoside Rg3 at a yield of 83.6 mg/L in a shake flask (7.0 mg/g dry weight, 21.12‐fold higher than with wild‐type cultures). The high‐production system established in this study could be a potential platform to produce the ginsenoside Rg3 commercially for pharmaceutical use. [ABSTRACT FROM AUTHOR]