A controlled approach for synthesizing CdTe quantum dots polyamidoamine nanocomposites

We develop a controllable approach to prepare ordered–CdTe quantum dots (QDs) polyamidoamine (PAMAM) nanocomposites (NCPs) by self-assembly growth of simple CdTe– PAMAM in aqueous solution. The sphere and network CdTe NCPs were obtained at pH 4.7 for growing 15 h and 79 h respectively. As the NCPs ceased growing over pH 8 immediately, we can conveniently control their size and morphology by adjusting pH of the solution to tune the growth time. The morphology change of CdTe-PAMAM nanocomposites was characterized by TEM images. The fluorescent intensity and photostability of ordered–CdTe–PAMAM have been improved significantly.     

Amplification-Free Detection of SARS-CoV-2 Down to Single Virus Level by Portable Carbon Nanotube Biosensors (Small 34/2023)

The rapid and sensitive detection of trace-level viruses in a simple and reliable way is of great importance for epidemic prevention and control. Here, a multi-functionalized floating gate carbon nanotube field effect transistor (FG-CNT FET) based biosensor is reported for the single virus level detection of SARS-CoV-2 virus antigen and RNA rapidly with a portable sensing platform. The aptamers functionalized sensors can detect SARS-CoV-2 antigens from unprocessed nasopharyngeal swab samples within 1 min. Meanwhile, enhanced by a multi-probe strategy, the FG-CNT FET-based biosensor can detect the long chain RNA directly without amplification down to single virus level within 1 min. The device, constructed with packaged sensor chips and a portable sensing terminal, can distinguish 10 COVID-19 patients from 10 healthy individuals in clinical tests both by the RNAs and antigens by a combination detection strategy with an combined overall percent agreement (OPA) close to 100%. The results provide a general and simple method to enhance the sensitivity of FET-based biochemical sensors for the detection of nucleic acid molecules and demonstrate that the CNT FG FET biosensor is a versatile and reliable integrated platform for ultrasensitive multibiomarker detection without amplification and has great potential for point-of-care (POC) clinical tests.     

湖南居民主要食品中锑的污染及暴露评估

目的掌握湖南省主要食品中锑的污染水平,评估湖南居民膳食中锑暴露安全性。方法运用湖南省常住居民营养与健康状况现状分析数据和2014—2015年湖南主要食品污染物监测数据,获得湖南地区居民膳食中锑暴露量,采用世界卫生组织规定锑的每日耐受摄入量(TDI)的限值,评价湖南居民从食物中摄入锑的安全性。结果粮食、蔬菜、水果、肉类、水产品、饮料、乳制品7类共1 445份食品样品中,锑检出率为80.8%(1 168/1 445),食品中锑含量的范围为ND~0.20 mg/kg,平均数为(0.046±0.17)mg/kg,中位数为0.008 4 mg/kg;湖南地区居民通过7类主要食品的锑暴露量为0.65μg/kg BW,安全限值(MOS)为9.2。蔬菜是膳食中锑暴露的主要来源,其贡献率为83.09%。结论湖南地区主要食品中锑的暴露水平未超过TDI值,MOS值1,居民膳食中锑暴露水平总体处于安全状态,但膳食中蔬菜类对锑暴露的贡献较大,值得关注。     

The elastic stabilization of multiple-height growth ledges during diffusional phase transformations

In diffusional phase transformations that proceed by the terrace-ledge-kink mechanism, both atomic-scale, unit-height ledges and multiple-height ledges are observed. Both types of ledges also have dislocation character, thereby making them disconnections. The dislocation interaction is shown to provide a strong stabilizing force for the multiple ledges and to lead to a capture distance for additional unit ledges that increases with ledge height. Implications for the mechanism of phase transformation are discussed.