Optical Detection of Acetone Using " Turn-Off" Fluorescent Rice Straw Based Cellulose Carbon Dots Imprinted onto Paper Dipstick for Diabetes Monitoring

Abstract

Persistent bad breath has been reported as a sign of serious diabetes health conditions. If an individual's breath has a strong odor of acetone, it may indicate high levels of ketones in the blood owing to diabetic ketoacidosis. Thus, acetone gas in the breath of patients with diabetes can be detected using the current easy-to-use fluorescent test dipstick. In another vein, rice straw waste is the most well-known solid pollutant worldwide. Thus, finding a simple technique to change rice straw into a valuable material is highly important. A straightforward and environmentally friendly approach for reprocessing rice straw as a starting material for the creation of fluorescent nitrogen-doped carbon dots (NCDs) has been established. The preparation process of NCDs was carried out via one-pot hydrothermal carbonization using NH₄OH as a passivation substance. A testing strip was developed on the basis of cellulose CD nanoparticles (NPs) immobilized onto cellulose paper assay. The NCDs demonstrated a quantum yield of 23.76%. A fluorescence wavelength was detected at 443 nm upon applying an excitation wavelength of 354 nm. NCDs demonstrated remarkable selectivity for acetone gas as their fluorescence was definitely exposed to quenching by acetone as a consequence of the inner filter effect. A linear correlation was observed across the concentration range of 0.5-150 mM. To detect and measure acetone gas, the present cellulose paper strip has a "switch off" fluorescent signal. A readout limit was accomplished for an aqueous solution of acetone as low as 0.5 mM under ambient conditions. The chromogenic fluorescence of the cellulose assay responsiveness depends on the fluorescence quenching characteristic of the cellulose carbon dots in acetone. A thin fluorescent cellulose carbon dot layer was deposited onto the surface of cellulose strips by a simple impregnation process. CDs were made using NP morphology and analyzed using infrared spectroscopy and transmission electron microscopy. The carbon dot distribution on the paper strip was evaluated by scanning electron microscope and energy-dispersive X-ray analysis. The absorption and fluorescence spectral analyses were investigated. The paper sheets' mechanical qualities were also examined.

Scheme 1. Preparation Method of NCDs

Figure 1

Effects of NH₄OH/CDA ratio on the quantum yield of NCDs.

Figure 2

Transmission electron microscopic graphs of NCDs.

Figure 3

X-ray diffraction spectral analysis of CDA (a), and NCDs (b).

Figure 4

FTIR spectra of CDA, and NCDs.

Figure 5

NCD-imprinted paper strips showing a white color under sunlight, and blue emission under UV irradiation.

Figure 6

Scanning electron microscopic images of S₁ (a–c) and S₈ (d–f).

Figure 7

Effects of NCDs total content on the mechanical features.

Figure 8

Fluorescence spectra of NCD-imprinted paper strip (S₆) after exposure to acetone at different contents (0.5–150 mM); F/F₀ as a function of acetone concentration is a linear correlation in the range of 0.5–150 mM: 0.5 (a), 25 (b), 50 (c), 70 (d), 90 (e), 110 (f), 130 (g), 150 (h) mM.

Figure 9

Selectivity of NCD-imprinted paper strip to acetone; emission spectra of NCD-imprinted paper strip in the existence of antibiotics, amino acids, and metallic cations at a fixed concentration of 100 μM.

Figure 10

Excitation spectrum of NCD-imprinted paper strip S₆ (top) and NCDs in aqueous solution under visible and UV lights (bottom).

Figure 11

Decay time of NCD-imprinted paper strip before (a) and after (b) exposure of acetone.

Figure 12

Reversibility of fluorescence at 443 nm (S₆).