Design,Assembly And Performance Of Graphene-Based And Aluminum-Based Nanosensors

In recent years,the nanosensors used for the detection of small molecules in vivo and toxic substances in food have attracted wide attentions at home and abroad.Among them,fluorescent sensors and surface-enhanced Raman scattering?SERS?sensors are favored for their simple operation,excellent sensitivity,high detection speed,and real-time detection.It is shown that the microstructures of fluorescent nanosensor and SERS sensor are closely related to the sensitivity and selectivity towards the detection of target molecules.Graphene possesses an easily modified two-dimensional conjugated structure and strong adsorption ability to the target molecules.Moreover,the rapid electron transfer in graphene is helpful to improve the sensitivity and selectivity of SERS and fluorescence sensors.In addition,Al is a better SERS substrate than glass because of its low price,easy to be obtained,and its own Raman enhancement activity.Based on these,in this paper,firstly,with graphene oxide?GO?acted as a fluorescence quencher of graphene quantum dots?GQDs?,and a novel fluorescence sensor for Cyt c detection was assembled,which possessed both a‘‘turn-off''mode and a‘‘turn-on''mode in various concentration ranges for Cyt c based on the different interaction among GO,GQDs,and Cyt c.Second,a patterned Al/RGO/Ag nanocomposite was prepared and used as an active substrate for the detection and catalytic degradation of malachite green in water.Finally,a plug-and-play type Al/Ag nano-SERS active substrate was prepared and used for the selective detection of melamine with low concentration.Subsequently,by modifying the microstructure of graphene-based and aluminum-based nanosensors,rapid,sensitive and selective detection of bio-small molecules?cytochrome c?and toxic substances in foods?malachite green and melamine?can be achieved.The main contents are as follows:A new class of fluorescence sensor?GQDs-GO?for cytochrome c?Cyt c?detection based on graphene quantum dots?GQDs?supported by graphene oxide?GO?has been developed through simply mixing a certain amount of GQDs and GO.It is found that fluorescence‘‘turn on''or‘‘turn off''can be adjusted easily according to the concentration of Cyt c.When the concentration of Cyt c is lower than 1.9?mol L^-1,the fluorescence is‘‘turn on'',whereas it is‘‘turn off''beyond 1.9?mol L^-1.The process is fast and can be completed within 10 s.By means of UV-vis absorption spectra,it is demonstrated that the changed fluorescence comes from the different interactions among GQDs,GO and Cyt c.Additionally,the GQDs-GO shows a high selectivity for Cyt c detection,and further exhibits favorable intracellular imaging in A549 cells.This study opens a new direction for developing a low-cost,highly efficient,GQDs-based fluorescence sensor for Cyt c detection,which make it very attractive for biological imaging applications.A patterned Al/RGO/Ag nanocomposite film was prepared by the layer-by-layer assembly technique combined with high-temperature calcination.The results showed that the patterned Al/RGO/Ag composite film had high stability and can be used as a SERS active substrate for rapid detection of malachite green with low concentration.It also showed good reproducibility for the detection of malachite green.Due to the strong interaction between RGO and Ag nanoparticles in the Al/RGO/Ag composite films,the patterned Al/RGO/Ag composite film exhibited better catalytic degradation activity for malachite green.The design and preparation method of the substrate will provide a useful reference for the design and performance research of other SERS active substrates used for the detection and degradation of the malachite green-like contaminants.A plug-and-play Al/Ag nano-SERS active substrate was rapidly prepared on the aluminum plate by displacement reaction.The results showed that,with the SERS substrate,the adsorption of silver nanoparticles on the supporting can be improved,and the detection for melamine can quickly achieved.This method was with the advantages of simple operation,low cost,and no damage detection,etc.The minimum detection limit can reach 10^-7 mol L^-1,and it was satisfied with the minimum standards for national food safety.In addition,the Al/Ag active substrate has an excellent reproducibility for melamine detection,continuously measured for 150 hours,the Raman intensity changed little.Moreover,the Al/Ag active substrate can selectively detect melamine in amines such as triethanolamine,N,N-dimethylformamide and 1,2-propanediamine.The study in this paper will be beneficial for the rapid construction of those sensors with high SERS activity,and also provide a basis for the design of novel sensors and rapid detection and degradation for toxic and hazardous substances in foods.