Su-Jeong Kim

Harnessing low energy photons (635 nm) for the production of H2O2 using upconversion nanohybrid photocatalysts

This study demonstrates, for the first time in literature, in situ photocatalytic synthesis of hydrogen peroxide (H2O2) through sensitized triplet–triplet annihilation (TTA) upconversion (UC) of low-energy, sub-bandgap photons. The aqueous phase TTA-UC and subsequent photocatalytic oxygen reduction were achieved by a newly developed ternary nanohybrid that consists of three components: (1) a nano-scale silica core–shell structure that encapsulates TTA-UC chromophore-containing media; (2) a low-bandgap CdS photocatalyst on the surface of the silica nanocapsule; and (3) a graphene oxide nanodisk (GOND) as a co-catalyst. In this study, we employed a benchmark TTA-UC chromophore pair, palladium(II) tetraphenyltetrabenzo-porphyrin sensitizer and 9,10-bis(phenylethynyl)anthracene acceptor, to upconvert red photons (λEx = 635 nm and 1.95 eV) to green photons (λEm = 505 nm and 2.45 eV). CdS is sensitized by upconverted green light to produce charge carriers, but not by incident red light without TTA-UC. The photogenerated electrons are efficiently transferred to a GOND to retard rapid charge recombination in CdS, which subsequently reduce dioxygen to produce H2O2 up to a 100 micromolar level per hour (or 3 mg L−1 h−1 with 0.5 g L−1 of GOND/CdS component only). Wrapping of CdS by a GOND was also found to markedly enhance the stability of CdS against photocorrosion without light shielding owing to its small size (ca. ∼80 nm) and transparency (α635nm = 1.85 g−1 dm3 cm−1).

The Correlation between Stem Characteristics and Its Resistance to Hail Damage in Potato Cultivars

BACKGROUND: Recently, weather disasters such as hail and typhoon occur frequently. These threaten the stable cultivation of potatoes. It is very important to cultivate potatoes with stable under unexpected weather disasters. This study was performed to investigate the correlation between mophological characteristics of potato stem and its resistance to hail damage in different potato cultivars. METHODS AND RESULTS: Hail fall occurred for 8 minutes on May 31, 2012 in the field of Highland Agriculture Research Center located in Jinbu-myeon Gangwon-do. Potato crop grown in the field was affected by hail due to which the stems of potato were broken. The percentage of broken stem of potato was investigated as the level of damage by hail. To determine the difference in the ratio of broken stem among the potato cultivars, physical characteristics of potato stem such as diameter and hardness were measured. To evaluate recovery phase after hail damage, ground coverage and yield were measured. The percentage of broken stem of cv. Goun and cv. Saebong were 30%, 26%, respectively, whereas it was 5% in the cv. Atlantic. Damage by hail was the lowest in cv. Atlantic. Diameter of the stem was 15 mm in cv. Atlantic, 13 mm in cv. Goun and 11 mm in cv. Saebong. The hardness of potato cultivars was measured which was 74 N in cv. Atlantic. 71 N in cv. Goun and 59 N in cv. Saebong. The ground coverage in cv. Atlantic was 79%, which was the highest followed by 73% in cv. Saebong and 56% in cv. Goun. The yield of cv. Atlantic was monitored at 90 days after planting which was 40 MT/ha and that of cv. Saebong was 36 MT/ha, whereas in cv. Goun, it was 30 MT/ha which was the lowest. CONCLUSION: The ratio of broken stem in cv. Atlantic was the lowest compared to cultivars. In the physical characteristics of stem, cv. Atlantic was the highest in value of diameter and hardness. Based on these results, it was considered that cv. Atlantic was resistant to hail damage compared to other cultivars.