Long wavelength emission multicolor fluorescent carbon quantum dots for the detection of pH, amino acids, and metal ions

•G-CQDs and YN-CQDs with long-wavelength multicolor emission were prepared by homologous hydrothermal method.•The QY of G-CQDs was up to 76.98 %, and the QY of YN-CQDs was 20.73 %.•G-CQDs can visually detect pH and dynamically quench specific detection of Asp, YN-CQDs can specifically detect Fe3+.•Both G-CQDs and YN-CQDs can be used for actual sample detection, showing high efficiency and reliability.