Fig 1

Construction of lithium ion crosslinked network and the RTP enhancement. a) The synthesis route of Li-CPDs and the schematic diagram of internal ionic bond crosslinked network. b) Photographs of PAA-CPDs and 1.5Li-CPDs powders under sunlight, 365 nm UV irradiation and after quenching, respectively."

Fig 2

The effect of crosslinking density regulation on luminescence properties. a) Photoluminescence spectra of PAA-CPDs and 0.5–3.0Li-CPDs powders under UV excitation (365 nm) and b) their total photoluminescence quantum efficiency. c) Phosphorescence spectra of PAA-CPDs and 0.5–3.0Li-CPDs powders with a delay time of 1 ms after excitation at 365 nm and d) their phosphorescence intensity emitted at 500 nm. e) The phosphorescence decay curve of PAA-CPDs and 0.5–3.0Li-CPDs powders after excitation at 365 nm and f) their phosphorescence lifetime."

Fig 3

Structural characterization of ionic bond crosslinked CPDs. a) TEM image of 1.5Li-CPDs. The scale is 30 nm. The inset is corresponding HRTEM. The scale is 5 nm. b) High-resolution Li 1s X-ray photoelectron spectroscopy. c) The stretching vibration diagram of C=O bond of carboxyl group and the corresponding wavenumber range, the symmetric stretching vibration and asymmetric stretching vibration diagram of carboxyl group and the corresponding wavenumber range. d) FTIR spectra of PAA-CPDs and 0.5–3.0Li-CPDs."

Fig 4

The universality of constructing ionic bond crosslinked network to enhance the RTP properties of CPDs. a) Photos of Na-CPDs, K-CPDs, Mg-CPDs and Ca-CPDs powders under sunlight, UV light (365 nm) and after quenching, respectively. b) Photoluminescence spectra and of PAA-CPDs, Na-CPDs, K-CPDs, Mg-CPDs and Ca-CPDs powders excited at 365 nm and d) their total photoluminescence quantum efficiency. c) Phosphorescence spectra of PAA-CPDs, Na-CPDs, K-CPDs, Mg-CPDs and Ca-CPDs powders at a delay time of 1 ms excited at 365 nm and e) their phosphorescence intensity."

Fig 5

Construction of ionic bond crosslinked network based on transition metal zinc ions to regulate RTP wavelength. a) Photographs of 0.5Zn-CPDs and 1.0Zn-CPDs powders under sunlight, 365 nm UV light and after quenching. b) Photoluminescence spectra of 0.5Zn-CPDs and 1.0Zn-CPDs powders under 365 nm excitation and c) the corresponding CIE coordinates. d) Phosphorescence spectra of 0.5Zn-CPDs and 1.0Zn-CPDs powders excited at 365 nm with a delay time of 1 ms. e) Phosphorescence decay curves of 0.5Zn-CPDs and 1.0Zn-CPDs powders with emission at 550 and 580 nm, respectively. f) PL spectra and g) phosphorescence spectra of 1.0Zn-CPDs powders at different excitation wavelengths (330, 360, 390, 420 nm)."