Detection Of Bacteria With Carbon Dots By Layer-by-layer Method

During the last years the development of new technologies,fast and precise for the detection of pathogenic microorganisms are of vital importance to ensure the quality of food,diagnosis of bacterial diseases,etc.Conventional techniques consume time,can be toxic and do not allow a detailed study of them.C-dots are a new class of fluorescent nanomaterials with excellent properties that could help solve this problem.For this reason,it has been proposed during this investigation the development of a structure that allows the detection of bacteria(E.coli)using immobilized C-dots for them.The methodology of LbL,which consists of electrostatic interaction,was applied in order to immobilize the C-dots to the outer membrane of the bacterium and then,create a solid structure.On the other hand,for the connection between these the following polyelectrolytes were used PDADMAC,PLL,PAAs and PSS.The formation of the structure and its function as a bacteria detection were evaluated with different techniques from fluorescence to spectroscopy.For Raman and SERS,an additional layer of AuNPs was added by LbL,to improve the detection signals and reduce the fluorescence of the C-dots.The results obtained showed that the structure was created and also,the intensity of the fluorescence is greater causing a better detection of the bacteria by fluorescence since the C-dots remain attached to the walls of the bacteria and do not pass through it.With respect to SERS,an increase in signal for the detection of bacteria was achieved when it is working with an array of B@C-dots@AuNPs.In conclusion,during this study,it was found an easy,fast,low-cost and non-toxic route for the immobilization of C-dots with other nanomaterials(AuNPs)for the detection of bacteria,in fluorescence and spectroscopy techniques such as SERS.