Synthesis and characterization of reporter molecules embedded core-shell nanoparticles as SERS nanotags

Surface-enhanced Raman scattering(SERS)spectroscopy is presented as a sensitive and spe-cific molecular tool for clinical diagnosis and prognosis monitoring of various diseases including cancer.In order for clinical application of SERS technique,an ideal method of bulk synthesis of SERS nanoparticles is necessary to obtain sensitive,stable and highly reproducible Raman signals.In this contribution,we determined the ideal conditions for bulk synthesis of Raman reporter(Ra)molecules embedded silver-gold core-shell nanoparticles(Au@Ra@AgNPs)using hydroquinone as reducing agent of silver nitrate.By using UV-Vis spectroscopy,Raman spectroscopy and transmission electron microscopy(TEM),we found that a 2∶1 ratio of silver nitrate to hydroquinone is ideal for a uniform silver coating with a strong and stable Raman signal.Through stability testing of the optimized Au@Ra@AgNPs over a two-week period,these SERS nanotags were found to be stable with minimal signal change occurred.The sta-bility of antibody linked SERS nanotags is also crucial for cancer and disease diagnosis,thus,we further conjugated the as-prepared SERS nanotags with anti-EpCAM antibody,in which the stability of bioconjugated SERS nanotags was tested over eight days.Both UV-Vis and SERS spectroscopy showed stable absorption and Raman signals on the anti-EpCAM conju-gated SERS nanotags,indicating the great potential of the synthesized SERS nanotags for future applications which require large,reproducible and uniform quantities in order for cancer biomarker diagnosis and monitoring.

Global desert variation under climatic impact during 1982-2020

Deserts are important landscapes on the earth and their variations have impacts on global climate through feedback processes.However,there is a limited understanding of the climatic controls on the spatial and temporal variations of global deserts.Here,we use climate reanalysis datasets,global land use/land cover(LULC)products and the CMIP6(Coupled Model Intercomparison Project)model outputs to calculate the changing of global deserts during 1982-2020,and estimate future spatial trends of global deserts.Our results show that mean annual global desert area over this period is 17.64×10^(6)km^(2),accounting for 12%of the terrestrial land.Desert areas decreased rapidly from the end of the 1980s to the 1990s in North Africa and Australia,followed by a slow expansion in early 21st century globally.Spatio-temporal variations of areas of arid climate are characterized by interdecadal fluctuations,and there are clear regional differences in dynamic s of the aridity index(AI,used here as a proxy for the area of drylands)and desert areas.Statistical analyses reveal that increased vegetation cover is directly related to the reduction of desert area,while potential evaporation,surface temperature and humidity are also significantly correlated with the desert area.The relationship between wind speed and desert dynamics varies regionally.The results of the CMIP6simulations suggest that global deserts will expand in the 21st century,albeit at different rates under the ssp245 and ssp585scenarios.Desert expansions are modelled to be greatest in Asia,Africa and Australia,while those of southern North Africa may reduce as their southern borders migrate northwards.