Mulberry‐Leaves‐Derived Red‐Emissive Carbon Dots for Feeding Silkworms to Produce Brightly Fluorescent Silk

Abstract

luminescent, and low-cost substances seems to be the optimal strategy to produce fluorescent silk. [9][10][11] Carbon dots (CDs) are the most competitive candidates for the above target, because they have shown outstanding biocompatibility and superior fluorescence in previous research such as bioimaging, [12,13] drug delivery, [14,15] and photothermal therapy. [16,17] In fact, many CDs are made from biomass, which guarantees the biosafety, low price, and green chemistry in CDs production. [18] In comparison with fluorescent organic dyes, rare earth nanoparticles, and semiconductor quantum dots, CDs would be the optimal choice for feeding silkworms. In 2019, blue-emissive CDs were first employed to feed silkworms, which produced blue-emissive silk with enhanced mechanical properties. [19] In the same year, blue-emissive CDs, CdSe/ZnS quantum dots, and rhodamine were fed to silkworms which produced the corresponding blue, green and red fluorescent silk, respectively. [20] By far, CDs-derived fluorescent silk with longer emission wavelengths has not been reported yet. The reasons lie in the state of the art for CDs. On one hand, there are only a few reports about red-emissive CDs with both high quantum yield (QY) and narrow emission peaks, and even fewer red-emissive CDs that could be made in a large scale at low cost. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] On the other, hydrophilic CDs are quickly discharged from the silkworm body and are not suitable for dyeing silkworms, while hydrophobic CDs are apt to accumulate excessively in the body and cause serious harm to silkworms, [10] because most of the hydrophobic CDs are made from aromatic compounds at present. [31,36] Therefore, it is really a challenge to synthesize hydrophobic red-emissive CDs from cheap biomass, which must adhere to the body and the silk of silkworms safely for a long time.After screening many routes and carbon sources, we find a green and sustainable approach to prepare deep-red-emissive CDs (R-CDs) from mulberry leaves. The as-prepared CDs have a main emission peak at 676 nm with a shoulder at 725 nm, possessing an full width at half maximum (FWHM) of 20 nm and QY of 73%. They are the brightest deep-red-emissive CDs so far to our knowledge. Since their strong red fluorescence can be observed by naked eyes under a wide range of excitation wavelengths from UV to red, even in the sunlight, the R-CDs-fed silkworms can be monitored under the visible light irradiation safely. During several months' observation, these R-CDs-fed Fluorescent silk has promising applications in dazzling textiles, biological engineering, and medical products, but the natural Bombyx mori silk has almost no fluorescence. Here carbon dots (CDs) made from mulberry leaves are reported, which have a strong near-infrared fluorescence with absolute quantum yield of 73% and a full width at half maximum of 20 nm. After feeding with such CDs, silkworms exhibit bright red fluorescence, grow healthily, cocoon normally, and turn to moths finally. The cocoons are ...

Application Progress of Green Carbon Dots in Analysis and Detection

“…In 2010, Zhao et al synthesized nitrogen-doped g-CDs with chitosan and D (+) glucosamine hydrochloride by hydrothermal method, [33] which laid a certain foundation for the preparing more g-CDs and opened the door to synthesize of g-CDs with natural products as carbon sources. More and more scholars are now synthesizing g-CDs with excellent properties, such as, Liu et al [34] used mulberry leaves to synthesize the deepest red emission, hydrophobic g-CDs (R-CDs). Based on the advantages of R-CDs' near-infrared fluorescence, good hydrophobicity, and biocompatibility, they were safely fed to silkworms, which could grow normally and healthily after eating R-CDs and showed red fluorescence, cocoon breaking moths for mating could produce normal fluorescent eggs, however, the control group of silkworms did not show red fluorescence.…”

Bioinspired silk fibroin materials: From silk building blocks extraction and reconstruction to advanced biomedical applications

“…These kind of bioinspired modification methods are probably quite effective for improving the biomedical performance for cell culture and tissue repair. Another example would be intrinsically luminescent silk materials produced through genetic engineering or altering the food of silkworms [ [169] , [170] , [171] , [172] , [173] , [174] , [175] , [176] ], which are useful for special biomedical usage. In addition, improved cytocompatibility, conductivity and mechanical properties, such as elastomeric properties and stretchability, may also be achieved through chemical or physical modification progress.…”

Synthesis, optical properties and applications of red/near-infrared carbon dots

“…glucose, lignin, fruits, vegetables, and leaves). [139][140][141][142][143][144][145][146] Ye reported the red C-dots using coal as the precursor, with a QY of 0.4% to 1.1%. 140 Ran used a thermalassisted electrochemical method to produce C-dots using coal slice as the precursor.…”

“…101 As earth-abundant and low-cost resources, biomass has been widely used for the synthesis of C-dots with tunable colours. 142,143 Liu et al reported the preparation of C-dots made from mulberry leaves. 143 The as-prepared CDs have a main emission peak at 676 nm with a shoulder at 725 nm, possessing a full width at half maximum of 20 nm and a QY of 73%.…”