Solvatochromic Surface-Passivated Carbon Dots for Fluorometric Moisture Sensing in Organic Solvents

Abstract

Herein, we reported the synthesis of solvatochromic, red fluorescence-emitting carbon dots (rCDs) from para-phenylenediamine (p-PD) by a one-step microwave-assisted solvothermal method. The effect of surface passivation with hydroxyl-enriched HBPs of varying generation numbers (G2 and G4) on the optical, physicochemical, and solvatochromic properties of the rCDs was evaluated. The quantum yield (QY) of rCDs was altered from 31.4% to 79.8% in EtOH when their surface was passivated with HBP-G4 (rCD-bis64); however, surface passivation of rCDs with HPBs did not alter the solvatochromic property of rCDs, where only a slight decay was observed in rCD-bis64. The solvatochromism of rCDs with a red-shifted fluorescence emission from green to red as a response to increased solvent polarity was used as a simple and economical quantitative analysis tool for naked-eye, fluorometric, and smartphone-applicable on-site detection of moisture in organic solvents by converting the digital images to RGB. The polarity-dependent fluorescence color switchability of rCDs and rCDs-bis64 was then applied for the visual analysis of surface characteristics of paper strips. The visual response of both CDs to the changing paper type was transformed to a color map of the paper surface that was further used for visual and quantitative analyses of surface properties of the filter papers.

Multicolor Emitting Carbon Dot-Reinforced PVA Composites as Edible Food Packaging Films and Coatings with Antimicrobial and UV-Blocking Properties

“…Red carbon dots (RCDs) were synthesized using the same method as previously reported. 63 First of all, 0.028 g of paraphenylenediamine was sonicated in 25 mL of ethanol/water (1:1, v/v) until a homogeneous solution was obtained. The obtained mixture was taken into Teflon containers and tightly closed.…”

Dual-emission carbon dots for sensitive fluorescence detection of metal ions and ethanol in water

“…2b, C 1s can be separated into three peaks at 284.88, 285.88 and 287.98 eV, corresponding to C–C/CC, C–N/C–O and CN, respectively. 53 N 1s (Fig. 2c) can be fitted into three peaks at 397.28, 399.02 and 400.06 eV, corresponding to pyridine N, pyrrole N and graphite N groups, respectively.…”

“…4b). The limit of detection (LOD) of Fe 3+ could be calculated by using the following formula (1): 53 LOD = 3 S / b where S represents the standard deviation of the fluorescence intensity of CDs when Fe 3+ is not added, and b represents the slope of the linear equation. According to calculation, LOD = 0.024 μM.…”

“…2b, C C]N, respectively. 53 N 1s (Fig. 2c) can be tted into three peaks at 397.28, 399.02 and 400.06 eV, corresponding to pyridine N, pyrrole N and graphite N groups, respectively.…”

High-quality full-color carbon quantum dots synthesized under an unprecedentedly mild condition

“…Similary, the other CQDs were prepared by replacing DETA with oPDA, mPDA, or pPDA. It should be noted, the masses of oPDA, mPDA, and pPDA were all controlled at 0.015 g. By referring to previous work, the as-synthesized solutions can be purified via silica column chromatography ( Ding et al., 2016 ; Alaş and Genç, 2021 ; Jia et al., 2019 ). It was found the mixture components were more beneficial on the applications of sensing metal ions.…”