Hexagonal boron nitride (h-BN) is the widest band gap 2D material (>6 eV), which has attracted extensive attention. For exploring potential applications in optoelectronic devices, electrical conductivity modulation (n or p type) is of extreme importance. Here, we report the achievement of a large-scale and high quality h-BN monolayer with p-type conductivity by modulation doping of Mg using a low pressure chemical vapor deposition method. A large-scale monolayer h-BN (>10 inches) was grown by using a wound Cu foil roll on a multi-prong quartz fork. Magnesium nitride is used as a dopant precursor in a separate line due to its appropriate melting point and decomposition temperature. Density functional theory calculations revealed that the acceptor level introduced by Mg is almost pinned into the valence band and the activated holes are highly delocalized into the surrounding h-BN lattices. The h-BN:Mg monolayer showed a p-type conductivity with a considerable surface current of over 12 μA and a hole density of 1.7 × 10 cm. The dielectrically tunable h-BN monolayer makes the fabrication of advanced 2D optoelectronic devices in short wavelength possible.

High carbonate alkalinity is one of the major stress factors for living organisms in saline-alkaline water areas. Acute and chronic effects of carbonate alkalinity on expression of two genes, carbonic anhydrase 2-like (CA2-like) and Na(+)-K(+)-ATPase α subunit (NKA-α) mRNA in medaka (Oryzias latipes) were evaluated to better understand the responses important for coping with a carbonate alkalinity stress. In the acute exposure experiment, the expression of CA2-like and NKA-α mRNA in the gill and kidney of medaka were examined from 0 h to 7 days exposed to 30.4 mM carbonate alkalinity water. Exposure to high carbonate alkalinity resulted in a transitory alkalosis, followed by a transient increase in gill and kidney CA2-like and NKA-α mRNA expression. In the chronic exposure experiment, the expression of these two genes was examined in the gill and kidney at 50 days post-exposure to six different carbonate alkalinity concentrations ranging from 1.5 to 30.4 mM. Gill and kidney CA2-like mRNA levels in 30.4 mM were approximately 10 and 30 times higher than that of the control (1.5 mM), respectively. Less differences were found in NKA-α expression in the 50-days exposure. The results indicate that when transferred to high carbonate alkalinity water, a transitory alkalosis may occur in medaka, followed by compensatory acid-base and ion regulatory responses. Thus, CA2-like and NKA-α are at least two of the important factors that contribute to the regulation of alkalinity stress.

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