Abstract:
Rhodamine dyes are widely used as fluorescent probes owing to their high absorption coefficient, broad fluorescence in the visible region of electromagnetic spectrum, high fluorescence quantum yield and photostability. A great interest in the development of new synthetic procedures for preparation of rhodamine derivatives has arisen in recent years because the probe must be covalently linked to another (bio)molecule or surface for most applications. To date, the emission wavelength of rhodamine dyes is always less than 600 nm, which restricts the practical application of rhodamines in living systems due to the serious background fluorescence interference. In this critical review the strategies for modification of rhodamine dyes and a discussion on the variety of applications of these new derivatives as fluorescent probes are given. Upon replacing the oxygen bridge atom by silicon, the resulting Si-rhodamines have been developed as novel near-infrared (NIR) fluorescent cores with remaining the key advantages of conventional rhodamine chromophore, and also generating the bathochromic shift in their emission wavelengths to NIR region. Based on the essential properties of Si-rhodamine, this paper mainly focuses on the principle of the red shift in the emission wavelength, the regulation of fluorescence wavelength and fluorescence quantum yield, and the design mechanism and application of Si-rhodamine fluorescent probes.