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 SiH or SiC 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. © 2014 Elsevier B.V. All rights reserved.
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