New fluorescent pH sensor based on label-free silicon nanodots

Silicon nanodots (SiNDs) are currently appealing to extensive studies due to their low toxicity and unique optical and electrical properties. In this work, we obtained label-free SiNDs via a facile hydrothermal method. The approach offers advantages in terms of cheap reactants, easy operation and a short time. The quantum yield (QY) of the SiNDs is up to 32.8%, and the as-prepared nanoparticles exhibit strong fluorescence (FL), higher photostability and obviously longer FL lifetime. More importantly, these label-free SiNDs can be used as a highly sensitive pH sensor, which FL respond rapidly to pH fluctuations and reveal a good linear relationship. Also, a superior pH-reversibility was demonstrated. Different salt ions show a little influence on the pH-responsive behavior. The pH of real water samples were tested on the basis of the proposed SiNDs sensor and the results are satisfactory. Further, traditional SiNDs with Si H or Si C surfaces make them less water-soluble or sensitive to the pH. Whereas, our SiNDs feature amino-terminated surface and these amino groups are conducive to the pH sensitivity. In a word, this new, cheap, low-toxic, and effective fluorescent pH sensor based on label-free SiNDs would be a promising candidate in biological field.