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In this study, we developed a novel galloyl group-functionalized polydiacetylene (Galloyl-PDA) sensor for colorimetric and fluorescent detection of Pb2+. Among three types of Galloyl-PDA vesicles prepared by changing the ratio of newly synthesized galloyl group-conjugated 10,12-pentacosadiynoic acid (Galloyl-PCDA) and matrix 10,12-tricosadinoic acid (TCDA), the blue Galloyl-PDA vesicles with 1:9 molar ratio of Galloyl-PCDA:TCDA showed the most dramatic color transitions to red with colorimetric response (CR) value of 46.66 ± 1.373% within 5 min upon addition of 50 μM Pb2+. However, they didn't exhibit any color change upon interaction with other heavy metals. Since the terminal galloyl moieties of the Galloyl-PDA vesicles could form coordination bonds with Pb2+, the Galloyl-PDA vesicles were stressed and showed obvious blue-to-red chromatic transitions. Besides, because the Galloyl-PDA vesicles exhibited nonfluorescent-to-fluorescent transitions, a linear response in colorimetric and fluorescent signals was observed in the range of 0–10 μM and 0.025–1 μM, respectively. From the colorimetric and fluorescent results, the limit of detection (LOD) was determined to be 1.329 μM and 0.068 μM, which is 8-fold and 12-fold better sensitivity than those of previously reported methods, respectively. Furthermore, the capability of our PDA sensor for detection of Pb2+ in tap water, river water, and human serum was validated with excellent precision and recovery rates of 97.14–100.0%, 99.05–103.3%, and 100.7–106.7%, respectively. As our PDA dual-signal sensor for Pb2+ is rapid, sensitive, specific, and detectable by the naked eye, this approach holds great promise for application in point-of-care testing (POCT). [Display omitted] • Dual-signal optical Galloyl-PDA sensors are developed for Pb2+ detection. • The LOD for chromatic and fluorescent detection is 1.329 and 0.068 μM, respectively. • The Galloyl-PDA sensors have excellent specificity for Pb2+ even in real samples. • The dual-signal PDA sensors are of great practical use as a POCT platform. [ABSTRACT FROM AUTHOR]

Polydiacetylene (PDA) is an attractive material due to its unique chromatic transition properties by external stimuli. Its blue-to-red color transitions observed by the naked eye make the PDA a promising optical biosensor. However, the chromatic transitions of most PDA materials are irreversible, leading to restricted applications of PDA-based biosensors. In this study, we suggest that the colorimetric reversibility of PDA by the thermal-photo stimuli cycles is closely related to the difference in hydrogen bond strength and ionic interactions between adjacent headgroups of PDA vesicles. By fabricating three types of PDA vesicles consisting of single or complex headgroups, their reversibility in color change was compared. The PDA vesicles composed of both carboxyl- and amine-terminated monomers (poly(PCDA/PCDA-EDA)) at a molar ratio of 1:1 exhibited noticeable chromatic reversibility with colorimetric response (CR) values of 84–91% and 24–61% during heating and UV irradiation cycles, respectively. And, the reversibility of the poly(PCDA/PCDA-EDA) vesicles under different pH conditions was examined to assess the effect of ionic interactions. To investigate the changes in the backbone and strength of hydrogen bonds in the prepared PDA vesicles, Raman and Fourier transform infrared (FT-IR) spectroscopies were executed, respectively. These results demonstrate that the hydrogen bond strength and ionic interactions of PDA vesicles with different terminal functional groups plays an important role in "red to blue" backward transitions, which can ultimately be applied to the development of recyclable PDA materials. [Display omitted] • A methodical approach to manipulate the colorimetric reversibility of polydiacetylene (PDA) is presented. • Three types of PDA vesicles consisting of single or complex headgroups are fabricated. • Poly(PCDA/PCDA-EDA) with complex headgroups exhibits distinct chromatic reversibility under thermal-photo stimuli cycles. • The PDA with stronger bonding force between headgroups shows reversible color transitions triggered by UV irradiation. • Structural alterations of PDA vesicles are intimately connected to their color response. [ABSTRACT FROM AUTHOR]

Geology and tectonics of the Korean Peninsula have been considered to be closely associated with those of the adjacent Chinese continent. Although Phanerozoic connections between the two areas have been reasonably well worked out, Precambrian ones are less well established. We obtained Sm–Nd and U–Pb garnet ages of 12 metamorphic rocks from widely separated parts of the Gyeonggi and Yeongnam massifs in South Korea to better understand their Precambrian history. The two massifs consist of late Archean to Paleoproterozoic basement rocks and Meso- to Neoproterozoic supracrustal rocks. Previous studies have shown that the two massifs experienced upper amphibolite to granulite facies metamorphism of medium pressure type with clockwise P–T-time paths, suggesting that the two massifs may represent remnants of a collisional orogen. Pb–Pb and U–Pb garnet ages give two distinct age groups: ten Paleoproterozoic (1989±34 to 1835±56 Ma) ages of basement rocks from the two massifs, and one late Permian (265±8 Ma) age of a supracrustal rock from the Gyeonggi massif that corroborates previous estimates of Permo-Triassic (298–245 Ma) metamorphic age for the supracrustal rocks. On the other hand, Sm–Nd garnet ages are less precise and display a wide range of ages from 2257 to 413 Ma for the basement rocks. When we compare the Sm–Nd and Pb–Pb ages from the same sample, the Sm–Nd age is similar to or younger than the Pb–Pb age, suggesting that the blocking temperature of the Sm–Nd garnet system may be lower than that of the U–Pb system (>800 °C). We interpret the Pb–Pb and U–Pb ages as representing the timing of metamorphic garnet growth, since the blocking temperature of the U–Pb garnet system is similar to or higher than the metamorphic temperature of the analyzed samples. Apparently, the younger metamorphism, possibly associated with the Permo-Triassic collision between the North and South China cratons, was not strong enough to reset the older metamorphic age. Similar Paleoproterozoic metamorphic ages for basement rocks of the two massifs suggest that they may have come from the same Precambrian terrane. The metamorphic ages of the basement rocks of South Korea agree very well with those of the Central Zone (orogenic belt) in the North China craton, suggesting a possible correlation between the two terranes. [Copyright &y& Elsevier]

Abstract We present chemical and Sr–Nd–Pb isotopic compositions of three Triassic (226–241 Ma) calc-alkaline granitoids (the Yeongdeok granite, Yeonghae diorite and Cheongsong granodiorite) and basement rocks in the northern Gyeongsang basin, south-eastern Korea. These plutons exhibit typical geochemical characteristics of I-type granitoids generated in a continental magmatic arc. The Yeongdeok and Yeonghae plutons have similar initial Sr, Nd and Pb isotope ratios (87 Sr/86 Srinitial = 0.7041 ~ 0.7050, ℇNd (t) = 2.3 ~ 4.0, 206 Pb/204 Pbfeldspar = 18.22 ~ 18.34), but distinct rare earth element patterns, suggesting that the two plutons formed from partial melting of a similar source material at different depths. The Cheongsong pluton has slightly more enriched Sr–Nd–Pb isotopic compositions (87 Sr/86 Srinitial = 0.7047 ~ 0.7065, ℇNd (t) = 3.9 ~ 2.8, 206 Pb/204 Pbfeldspar = 18.24 ~ 18.37) than the other two plutons. The Nd model ages of the basement rocks (1.1 ~ 1.4 Ga) are slightly older than those of the plutons (0.6 ~ 1.0 Ga). The initial Sr and Nd isotopic ratios of the plutons can be modeled by the mixing between the mid-oceanic ridge basalt-like depleted mantle component and the crustal component represented by basement rocks, which is also supported by Pb isotope data. The Sr and Nd isotope data from granitoids and basement rocks suggest that the Gyeongsang basin, the Hida belt and the inner zone of south-western Japan share relatively young basement histories (middle Proterozoic), compared with those (early Proterozoic to Archean) of the Gyeonggi and Yeongnam massifs and the Okcheon belt. The Nd isotope data of basement rocks suggest that the Hida belt might be better correlated with the basement of the Gyeongsang basin than the Gyeonggi massif, the Okcheon... [ABSTRACT FROM AUTHOR]

Abstract: We report the Sr, Nd and Pb isotopic ratios of clinopyroxene separates from spinel peridotite xenoliths hosted by late Cenozoic alkali basaltic rocks from Baengnyeong Island, Jogokni, and Jeju Island, all near the southeastern margin of the Sino-Korean Craton in South Korea. Measured Sr, Nd and Pb isotopic compositions in the clinopyroxene separates show, in general, simple trends between depleted MORB-like mantle (DMM) and relatively enriched components, which can be explained by old event(s) of infiltration by metasomatic melts/fluids that enriched a precursor time-integrated depleted mantle in incompatible trace elements and overprinted its isotopic composition. Comparison of the xenoliths with the host basalts suggests that infiltration of carbonatitic melts can explain the characteristics of the Baengnyeong xenoliths while reaction with residual slab-derived melt/fluid subjected to amphibole and phlogopite fractionation explains the Jogokni xenoliths best, ruling out direct influence of the magmatism that produced the host basalts. On the other hand, the Jeju clinopyroxene separates display a mixing hyperbola between DMM and the host basalts in Sr–Pb and Nd–Pb isotope correlation diagrams, suggesting some influence by liquids similar to the host basalts. The Korean xenoliths tend to be similar in the overall range of their mineralogic modes, elemental compositions, and Sr–Nd–Pb isotopic ratios to those of the fertile peridotite xenoliths derived from the post-Archean lithospheric mantle of eastern China, and yet without any compositional evidence for a refractory Archean mantle root. Overall comparison of the measured isotopic compositions for these Korean xenoliths with available data on lavas from eastern China, indicates that the dominant enriched mantle source components for the Cenozoic intraplate volcanism in the East Asia (EM1 for northeast China, and EM2 for Southeast Asia) are absent in the lithospheric mantle beneath the region. The Cenozoic intraplate volcanism, therefore, must have originated in the asthenosphere. [Copyright &y& Elsevier]