Xuegang Gong,Xiaoyong Liao,You Li,Hongying Cao,Yishu Zhao,Haonan Li,Daniel P. Cassidy
A simple surface-enhanced Raman spectroscopy (SERS) sensor based on an undecorated gold-colloid substrate was developed for the rapid and effective detection of polycyclic aromatic hydrocarbons (PAH). The SERS enhancement of the bare Au nanoparticles for PAH was achieved by adjusting chemical reduction conditions and Cl− content. The strongest SERS response of this system was achieved with 2.0 mL of trisodium citrate (1%) and 80 μL of NaCl (1 M). With this simple SERS sensor, qualitative and quantitative determination of trace-level naphthalene (NaP), phenanthrene (PHE) and pyrene (PYR) were achieved using a portable Raman spectrometer at detection limits of 1.38 μg L−1, 0.23 μg L−1, and 0.45 μg L−1, respectively. Plots of SERS intensity vs. PAH concentrations were linear, with correlation coefficients (R2) ranging from 0.8729 to 0.9994. More importantly, the SERS sensor was able to accurately identify each PAH in complex mixtures. This SERS technique shows great promise for the rapid and direct detection of aromatic hydrocarbons organic pollutants in field.
Ning Gan,Xiaowen Du,Yuting Cao,Futao Hu,Tianhua Li,Qianli Jiang
An ultrasensitive portable electrochemical immunosensor for human immunodeficiency virus p24 (HIV p24) antigen detection has been developed, whereby the detection sensitivity was 1000 times higher than that of the ELISA method. Firstly, a novel HRP enzyme–antibody copolymer (EV-p24 Ab2) was synthesized through an EnVision regent (EV, a dextrin amine skeleton anchoring more than 100 molecules of HRP and 15 molecules of anti IgG), then incubated in the secondary antibody of p24. Secondly, the copolymer was immobilized on the gold nanocolloids (AuNPs) to fabricate a novel signal tag (AuNPs/EV-p24 Ab2). Subsequently, a sandwich-type immunoreaction would take place between the capture probe (silicon dioxide-coated magnetic Fe3O4nanoparticles (MNPs) labeled with the primary p24 antibody (MNPs-p24 Ab1)), p24 (different concentrations) and the signal tag [AuNPs/EV-p24 Ab2)] to form the immunocomplex. Finally, the immunocomplex was absorbed on the surface of screen printed carbon electrode (SPCE) by a magnet and immersed in the o-hydroxyl phenol (HQ) and H2O2. The large amounts of HRP on the signal tag can catalyze the oxidation of HQ by H2O2, which can induce an amplified reductive current. Moreover, the capture probe could improve the accumulation ability of p24 and facilitate its separation from the substrate through the magnet. Under optimal conditions, the proposed immunoassay exhibited good sensitivity to p24 within a certain concentration range from 0.001 to 10.00 ng/mL, with a detection limit of 0.5 pg/mL (S/N = 3). The proposed method can be used for real-time and early detection of HIV-infected people.
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