Carbon dots with both red-emission and red-excitation (R-CDs) have attracted much attention due to their excellent optical property and promising application in various fields. However, most carbon dots (CDs) with red-emission are only excited with short wavelength irradiation, which heavily hinders their further applications. Herein, novel R-CDs are obtained through a hydrothermal synthesis by using p-phenylenediamine and ammonium thiocyanate as precursors. The as-synthesized R-CDs exhibit a strong red emission at 618 nm at a long excitation (598 nm). Moreover, the R-CDs are explored as a selective and sensitive “turn-off” sensor for Sn²⁺ detection by the non-radiative recombination of the excitons through effective electron, charge or energy transfer between Sn²⁺ and surface functional groups such as hydroxyl, carbonyl, amine, thiophene, and SO, with a detection range from 0 to 90 μM and a detection limit of as low as 17.25 nM.

具有红光和红光激发的碳点（R-CDs）由于其优异的光学性能和在各个领域的应用前景而备受关注。然而，大多数具有红光发射的碳点（CD）仅在短波长照射下才被激发，这严重阻碍了它们的进一步应用。在此，通过使用对苯二胺和硫氰酸铵作为前体，通过水热合成获得新型 R-CD。合成的 R-CD 在长激发 (598 nm) 下在 618 nm 处表现出强烈的红色发射。此外，通过激子的非辐射复合，通过 Sn ²⁺之间的有效电子、电荷或能量转移，R-CD 被探索为选择性和灵敏的“关闭”传感器，用于 Sn ²⁺检测。和表面官能团，如羟基、羰基、胺、噻吩和SO，检测范围从0到90 μM，检测限低至17.25 nM。