Fluorescent Nano-Biomass Dots: Ultrasonic-Assisted Extraction and Their Application as Nanoprobe for Fe3+ detection

Abstract

Biomass as sustainable and renewable resource has been one of the important energy sources for human life. Herein, luminescent nano-biomass dots (NBDs) have been extracted from soybean through ultrasonic method, which endows biomass with fluorescence property. The as-prepared NBDs are amorphous in structure with an average diameter of 2.4 nm and show bright blue fluorescence with a quantum yield of 16.7%. Benefiting from the edible raw materials and heating-free synthesis process, the cytotoxicity test shows that the cell viability still keeps 100% even if the concentration of the NBDs reaches 800 μg/ml, indicating the good biocompatibility of the NBDs. In addition, the fluorescence of the NBDs is very sensitive to Fe³⁺, which can be used for Fe³⁺ detection in terms of their health superiority. The limit of detection (LOD) of the proposed sensor was determined as 2.9 μM, which is lower than the maximum allowable level of Fe³⁺ (5.37 μM) in drinking water.

Keywords: Fe3+ detection; Fluorescence; Nano-biomass dots; Nanoprobe; Ultrasonic methods.

Scheme 1

Schematic illustration of the preparation process of the NBDs from soybeans

Fig. 1

TEM images of the NBDs (a) and (b). c The particle size distribution of the NBDs. HAADF image (d) and corresponding elemental distribution mapping of carbon (e), nitrogen (f), and oxygen (g)

Fig. 2

a XRD pattern of the NBDs. b FTIR spectra of the soybean and NBDs. c XPS survey spectrum of the NBDs. High-resolution XPS spectra of C 1s (d), N 1s (e), and O 1s (f)

Fig. 3

a Fluorescence spectra of the NBDs with excitation wavelength changes from 320 to 520 nm. b UV-Vis absorption spectra of the NBDs. c Fluorescence spectra of the NBDs at different temperature, the inset is the plot of the fluorescence intensity of the NBDs as a function of temperature. d Fluorescence intensity and images of the NBD powders under the illumination of a 365-nm lamp for different duration and those of the NBD powders at different measuring temperature

Fig. 4

Viability of HeLa cells after 72 h of incubation with different concentrations of NBDs and CDs

Fig. 5

a PL spectra of the NBDs in the presence of different concentrations of Fe³⁺. b Calibration curve of the sensor as a function of Fe³⁺ concentration. c Fluorescence intensities of the NBDs in the presence of different ions. d Photographic images of the NBDs solution with different metal ions under indoor and UV illumination

Fig. 6

a Fluorescence decay traces of the NCDs in the absence and presence of Fe³⁺ under excitation at 370 nm and emission at 445 nm. b Schematic illustration for the possible fluorescence quenching mechanism of the NBDs in the presence of Fe³⁺ ions