Abstract
Herein, a novel label-free photoelectrochemical (PEC) immunosensor based on SnS2@mpg-C3N4 nanocomposite is fabricated for the detection of prostate specific antigen (PSA) in human serum. Firstly, mesoporous graphite-like carbon nitride (mpg-C3N4) with carboxyl groups is synthesized successfully which possesses high specific surface area and large pore volume. Then, SnS2 as a typical n-type semiconductor with weak photoelectric conversion capability is successfully loaded on carboxylated mpg-C3N4 to form a well-matched overlapping band-structure. The as-synthesized SnS2@mpg-C3N4 nanocomposite performs outstanding photocurrent response under visible-light irradiation due to low recombination rate of photoexcited electron-hole pairs, which is transcend than pure SnS2 or pure mpg-C3N4. It is worth noting that SnS2@mpg-C3N4 nanocomposite is firstly employed as the photoactive material in PEC immunosensor area. The concentration of PSA can be analyzed by the decrease in photocurrent resulted from increased steric hindrance of the immunocomplex. Under the optimal conditions, the developed PEC immunosensor displays a liner photocurrent response in the range of 50 fg·mL−1 ~ 10 ng·mL−1 with a low detection limit of 21 fg·mL−1. Furthermore, the fabricated immunosensor with satisfactory stability, reproducibility and selectivity provides a novel method for PSA determination in real sample analysis.
Highlights
Prostate specific antigen (PSA), a kind of kallikrein-like serine protease, is secreted by prostatic epithelial cells
The morphological structures of the as-synthesized materials were investigated by transmission electron microscope (TEM) and field emission scanning electron microscope microscope (FESEM)
Compared with mpg-C3N4, the Fourier Transform Infrared Spectoscopy (FT-IR) spectra of carboxylated mpg-C3N4 has a characteristic absorption peak at 1692 cm−1 and 1206 cm−1 corresponding to the stretching mode of C=O band and the stretching mode of C-OH, which prove that carboxyl groups has been introduced successfully[34]
Summary
Prostate specific antigen (PSA), a kind of kallikrein-like serine protease, is secreted by prostatic epithelial cells. Among kinds of newly developed analytical techniques, the photoelectrochemical (PEC) immunosensor have numerous advantages, such as good selectivity, high sensitivity, fast analysis speed and low cost, etc[6,7,8]. Photoelectric conversion efficiency limits its further practical applications due to the high recombination rate of photoexcited electron-hole pairs. To improve this situation for better applications, many methods have been carried out, such as doping with other elements, morphology control and compositing with other semiconducting materials[23,24,25]. The as-synthesized SnS2@mpg-C3N4 nanocomposite had a better PEC response benefiting from the well-matched overlapping band potentials which greatly reduced the recombination rate of photoexcited electron-hole pairs, and as a consequence, high photocurrent response was produced. What’s more, as an electron donor, ascorbic acid (AA) inhibited the recombination of photoexcited electron-hole pairs, and to some extent it increased the photocurrent
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