Changchun University of Science and Technology

About: Changchun University of Science and Technology is a education organization based out in Changchun, China. It is known for research contribution in the topics: Laser & Luminescence. The organization has 11191 authors who have published 8833 publications receiving 64473 citations.

Surface Chemistry Routes to Modulate the Photoluminescence of Graphene Quantum Dots: From Fluorescence Mechanism to Up‐Conversion Bioimaging Applications

Abstract: The bandgap in graphene-based materials can be tuned from 0 eV to that of benzene by changing size and/or surface chemistry, making it a rising carbonbased fl uorescent material. Here, the surface chemistry of small size graphene (graphene quantum dots, GQDs) is tuned programmably through modifi cation or reduction and green luminescent GQDs are changed to blue luminescent GQDs. Several tools are employed to characterize the composition and morphology of resultants. More importantly, using this system, the luminescence mechanism (the competition between both the defect state emission and intrinsic state emission) is explored in detail. Experiments demonstrate that the chemical structure changes during modifi cation or reduction suppresses non-radiative recombination of localized electron-hole pairs and/or enhances the integrity of surface π electron network. Therefore the intrinsic state emission plays a leading role, as opposed to defect state emission in GQDs. The results of time-resolved measurements are consistent with the suggested PL mechanism. Up-conversion PL of GQDs is successfully applied in near-IR excitation for bioimaging.

Granitoids of the Central Asian Orogenic Belt and Continental Growth in the Phanerozoic

Abstract: The Central Asian Orogenic Belt (CAOB), also known as the Altaid Tectonic Collage, is characterised by a vast distribution of Paleozoic and Mesozoic granitic intrusions. The granitoids have a wide range of compositions and roughly show a temporal evolution from calcalkaline to alkaline to peralkaline series. The emplacement times for most granitic plutons fall between 500 Ma and 100 Ma, but only a small proportion of plutons have been precisely dated. The Nd-Sr isotopic compositions of these granitoids suggest their juvenile characteristics, hence implying a massive addition of new continental crust in the Phanerozoic. In this paper we document the available isotopic data to support this conclusion. Most Phanerozoic granitoids of Central Asia are characterised by low initial Sr isotopic ratios, positive eNd(T) values and young Sm—Nd model ages (TDM) of 300-1200 Ma. This is in strong contrast with the coeval granitoids emplaced in the European Caledonides and Hercynides. The isotope data indicate their ‘juvenile’ character and suggest their derivation from source rocks or magmas separated shortly before from the upper mantle. Granitoids with negative eNd(T) values also exist, but they occur in the environs of Precambrian microcontinental blocks and their isotope compositions may reflect contamination by the older crust in the magma generation processes. The evolution of the CAOB is probably related to accretion of young arc complexes and old terranes (microcontinents). However, the emplacement of large volumes of post-tectonic granites requires another mechanism, probably through a series of processes including underplating of massive basaltic magma, intercalation of basaltic magma with lower crustal granulites, partial melting of the mixed lithologic assemblages leading to generation of granitic liquids, followed by extensive fractional crystallisation. The proportions of the juvenile or mantle component for most granitoids of Central Asia are estimated to vary from 70% to 100%.

Thermal evolution of Archean basement rocks from the eastern part of the North China craton and its bearing on tectonic setting

Abstract: The basement rocks in the eastern zone of the North China craton are composed predominantly of pretectonic tonalitic-trondhjemitic-granodioritic gneisses and syntectonic granitoids, with rafts of supracrustal rocks consisting of ultramafic to felsic volcanic and sedimentary rocks, metamorphosed over a range of conditions from greenschist to granulite facies. Most mafic granulites, amphibolites, and some pelitic gneisses and schists preserve the prograde, peak, and post-peak textures. The prograde metamorphic stage is indicated by mineral inclusions within minerals of the peak stage, represented by the assemblages of hornblende + plagioclase + quartz ± biotite in mafic granulites, chlorite + actinolite + epidote + plagioclase + quartz in amphibolites, and biotite + plagioclase + quartz in pelitic gneisses. The peak stage is shown by assemblages of orthopyroxene + clinopyroxene + garnet + plagioclase + quartz in the mafic granulites, hornblende + plagioclase + quartz + garnet in garnetiferous amphibolites, ...