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Synthesis of carbon quantum dots from lac dye for silicon dioxide imaging and highly sensitive ethanol detecting
摘要： This study aimed to improve the fluorescence performance of lac dye by preparing carbon quantum dots in an attempt to diversify the applicability of lac dye in fluorescence detection. The highly photoluminescent (PL) ld-CQDs were synthesized for the first time using lac dye as a precursor by a facile, green, one-pot ethanol thermal method. The ld-CQDs were neither soluble nor dispersed in water, but could be dissolved or dispersed in organic solvents. The ld-CQDs were well dispersed in ethanol with a mean diameter of 1.76 nm and were found to emit a bright yellow fluorescence with an emission wavelength of 570 nm. The quantum yield of ld-CQDs was 0.40, which was a significant 20-fold improvement over the lac dye of 0.02. Meanwhile, ld-CQDs exhibited pH-sensitive and excellent affinity for silicon dioxide without further chemical modification. Further, ld-CQDs could be used to image silicon dioxide since the fluorescence intensity of the ld-CQDs/silicon dioxide composites was significantly improved. Furthermore, the ld-CQDs could be used as a highly sensitive fluorescent probe to detect the ethanol content of commercial wines. In conclusion, this study has demonstrated the novel application of the fluorescence properties of the lac dye, which has utility in visual detection applications and in tracking the detection of silicon dioxide and ethanol.
关键词： novel application,carbon quantum dots,photoluminescent,Lac dye
更新于2025-11-20 15:33:11
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FT-Raman Analyses of Blue Dyes Stuff Common in Swedish Folk Art from H?lsingland during 18th and 19th Century
摘要： The overall aim of this study is to gain a better understanding of the historic use of woad in Sweden in the 18th and 19th centuries. A key question is, whether it is possible to distinguish between indigo from woad and exotic indigo using Raman spectroscopy? Reference samples prepared according to historic recipes using woad, exotic indigo, logwood and brazilwood - were used to dye different textile fibres - cotton, wool and linen. In addition, various reference compounds - indigotin, indirubin, kaempferol, luteolin, 3-hydroxyflavone and tryptanthrin - as well as the ‘flower’ of the woad dye bath were analysed to identify specific fingerprint regions for each compound. Blue threads from four historic textiles - a skirt and three rag balls - from the region of H?lsingland were then analysed in comparison to the references. A specific peak at 993 cm-1 was identified in the spectra taken from the flower of the woad vat, which we suggest possibly arises from 3-hydroxyflavone. DSA-ToF-MS analysis suggests flavone- glycosides as possible candidates. However, cellulosic substrates show a broad vibration at 999 cm-1 overlapping the flavone signature, thus rendering it non-diagnostic, but it might be possible to use this peak in Raman analyses supported by mass spectrometry to distinguish between indigo from woad and exotic indigo if the substrate is wool or if it is a pigment. Raman analyses of the historic samples identify the colourants as indigo and possibly woad and logwod mixed with brazilwood.
关键词： DSA-Tof-MS,Dyestuff,Lac pigments,FT-Raman,Colouring matters
更新于2025-11-14 15:16:37
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The Power of (Near) Simultaneous Multi-Frequency Observations for mm-VLBI and Astrometry
摘要： Simultaneous or near-simultaneous observations at multiple frequency bands have the potential to overcome the fundamental limitation imposed by the atmospheric propagation in mm-VLBI observations. The propagation effects place a severe limit in the sensitivity achievable in mm-VLBI, reducing the time over which the signals can be coherently combined, and preventing the use of phase referencing and astrometric measurements. We present two demonstrations of the power of (near) simultaneous multi-frequency observations with the KVN and VLBA, and our recently developed analysis strategies to enable new measurements at mm-VLBI. The first case comprises simultaneous observations at 22, 43, 87 and 130 GHz of a group of five AGNs, the weakest of which is ～200 mJy at 130 GHz, with angular separations ranging from 3.6 to 11 degrees, using the KVN. We analysed this data using the Frequency Phase Transfer (FPT) and the Source Frequency Phase Referencing (SFPR) techniques, which use the observations at a lower frequency to correct those at a higher frequency. The results of the analysis provide an empirical demonstration of the increase in the coherence times at 130 GHz from a few tens of seconds to about twenty minutes, with FPT, and up to many hours with SFPR. Moreover the astrometric analysis provides high precision relative position measurements between two frequencies, including, for the first time, astrometry at 130 GHz. The second case is a variation of the above, whereby adding dedicated wide-band cm-wavelength observations to measure the ionosphere eliminates the need for a second, calibrator, source. This addresses the scarcity of calibrators at mm-VLBI. We dubbed this technique Multi Frequency Phase Referencing (MFPR). We present bona fide astrometrically aligned VLBA images of BL Lacertae at 22 and 43 GHz using MFPR, which, combined with results from conventional phase referencing at cm-wavelengths, suggests the VLBI core has a recollimation shock that is revealed at mm-wavelengths. These shocks could be responsible for the γ-ray emission in blazar jets.
关键词： radio continuum,BL Lac,astrometry,galaxies: 1803+784, 1807+698, 1842+681, 1928+738, 2007+777,interferometric
更新于2025-09-09 09:28:46
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In vitro assessments of white-spot lesions treated with NaF plus tricalcium phosphate (TCP) toothpastes using synchrotron radiation micro computed tomography (SR micro-CT)
摘要： Synchrotron radiation micro-computed tomography (SR micro-CT), considered superior to standard polychromatic micro-CT techniques, was used to assess the densities of bovine enamel white-spot lesions (WSL) treated in a 10-day pH cycling model with either: (A) Clinpro Tooth Crème (0.21% NaF plus TCP), (B) Clinpro 5000 (1.1% NaF plus TCP) or (C) Tom’s of Maine (0% NaF) dentifrice. Each day consisted of four 2 min treatments, one 4 h acid challenge (pH=5.0), and immersion in artificial saliva (pH=7.0) between these events. After 10 days, WSL specimens were evaluated for lesion depth using confocal microscopy and lesion density using SR micro-CT with depths ranging from 2.76 to 113.16 μm, in 2.76 μm slice increments. Statistical analyses (Student’s t-test) were performed at the 95% confidence level. SR micro-CT analyses revealed the NaF plus TCP dentifrices improved WSL densities relative to the fluoride-free toothpaste, and is consistent with an earlier study utilizing polychromatic micro-CT. In contrast to previous findings, SR micro-CT analyses also revealed significant differences in WSL densities treated with the two NaF dentifrices at enamel depths of 13.80, 16.56, and 19.32 μm. These findings suggest SR micro-CT may be especially suited for detecting density differences in lesions sensitive to fluoride-driven remineralization processes.
关键词： X-ray linear attenuation coefficient (X-ray LAC),synchrotron radiation micro computed tomography (SR micro-CT),density,Toothpaste,monochromatized X-ray beams,fluoride,remineralization
更新于2025-09-09 09:28:46