In a paper published in the journal ACS Applied Nano Materials, a simple, eco-friendly, and sustainable technique was presented for separating, converting, and utilizing lignocellulose components.
Study: Lignin-Derived Carbon Dot/Cellulose Nanofiber Films for Real-Time Food Freshness Monitoring. Image Credit: New Africa/Shutterstock.com
In this paper, the researchers highlighted the sustainable and eco-friendly use of lignocellulose and revealed the potential of composite films based on carbon dots for on-site food monitoring.
Why is Food Monitoring Important?
Excess formation or consumption of biogenic amines (BAs) found in some food items can prove detrimental to human health.
Biogenic amines are primarily produced by enzymatic decarboxylation of amino acids and reductive amination of aldehydes and ketones. Biogenic amines are important indicators for determining the quality and freshness of food.
Carbon Dots for Fluorescence Sensing
Carbon dots are a newly developed form of fluorescent carbonaceous substance that shows controllable photoluminescence and strong biocompatibility.
The interaction between carbon dots and analytes can be controlled by varying the surface features and the sizes of carbon dots. Carbon dots are therefore highly promising candidates for fluorescence detection systems.
Biomass conversion has emerged as a viable option for converting biomass into carbonaceous nanomaterials for various useful purposes, including detection and cell imaging.
Role of Cellulose in the Synthesis of Carbon Dots
Lignocellulose, a combination of lignin, cellulose, and hemicellulose, is an inexpensive, biocompatible, and renewable biomass source of carbon.
In lignocellulose, lignin is a type of aromatic polymer having a large concentration of carbon and numerous oxygen-containing functional groups and may be employed as a source for carbon-based materials.
Using waste lignin as a precursor for the synthesis of carbon dots, therefore, offers a viable and inexpensive manufacturing technique for carbon dots.
Some carbon dots possess a distinct pH response property, considerably expanding their applicability in smart sensing and detection.
To compensate for the decreased fluorescence stability of carbon dots resulting from agglomeration-induced fluorescence quenching, carbon dots may be enclosed within the matrix to restrict their mobility and ensure uniform dispersion.
Encapsulating carbon dots inside a matrix stabilizes carbon dot fluorescence and allows for real-time and portable detection.
The Advantages of Using Cellulose Nanofiber
Cellulose-based sheets are far more appealing than synthetic polymeric sheets because they are organic, renewable, biocompatible, and biodegradable.
Cellulose nanofibers, derived from organic cellulose materials, exhibit excellent strength, modifiability, and controllable morphology, making them a suitable platform for stimulus-responsive functional materials.
Cellulose nanofibers may offer additional active sites and binding channels because of their flexible nanofiber structure and high aspect ratio. Moreover, cellulose nanofibers with carboxyl groups are more conducive to subsequent chemical modification to alter their functions and characteristics for broader uses.
Research Methodology
The team utilized an eco-friendly deep eutectic solvent (DES) framework as a pretreatment platform to isolate lignocellulose biomass residual poplar sawdust.
First, lignin-derived carbon dots were produced, and they demonstrated good fluorescence capabilities as well as good pH responsiveness.
Red-emitting carbon dots were employed as a marker in developing a ratiometric fluorescent probe for detecting biogenic amines.
The isolated cellulose was oxidized and homogenized to produce cellulose nanofibers, which were then used as the matrix to fabricate a smart pH-responsive carbon dot and cellulose nanofiber film.
By producing a confinement effect, the internal hydrogen bonding among carbon dots and cellulose nanofibers could successfully stabilize the fluorescence of carbon dots.
Coupling this fluorescence detection system with a smartphone could offer a potential technique for using biomass-based substances in sensing applications.
Important Takeaways
In this study, the team successfully isolated lignocellulose constituents via a DES method and achieved their hierarchical utilization.
The lignin was used to synthesize fluorescent carbon dots to develop a ratiometric fluorescent probe for visually detecting biogenic amines.
This resulted in an effective approach for synthesizing lignin-doped carbon dots from inexpensive biomass and developing a fluorescent platform based on carbon dots for food monitoring.
The fabrication of cellulose nanofibers opened the possibility of fabricating flexible films for sensing systems.
Based on this, a composite film of carbon dots and cellulose nanofibers was created as a portable and cost-effective label for visually monitoring the freshness of food items like shrimp and pork.
The findings of this research encouraged the development of sustainable analysis techniques using organic materials. The paper presented a method for building a quick, visual, and real-time food monitoring and assessment platform.
Reference
Si, L., Shi, Z., Hou, J., Miao, C., Hou, Q., Xu, Z., & Ai, S. (2022). Lignin-Derived Carbon Dot/Cellulose Nanofiber Films for Real-Time Food Freshness Monitoring. ACS Applied Nano Materials. Available at: https://pubs.acs.org/doi/10.1021/acsanm.2c03675
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