Lignosulfonate: A Convenient Fluorescence Resonance Energy Transfer Platform for the Construction of a Ratiometric Fluorescence pH-Sensing Probe

Recent developments in lignin-based fluorescent materials

Biomass-based fluorescent materials are an alternative to plastic-based materials for their multifunctional applications. Lignin, an inexpensive and easily available raw material, demonstrates outstanding environment-responsive properties such as pH, metal ions, dyes sensing, bioimaging and so on. To date, only a little work has been reported on the synthesis of lignin-based fluorescent materials. In this review report, synthetic approaches and light-responsive applications of lignin-based fluorescent carbon dots and other materials are summarized. The results reveal that lignin-based fluorescent carbon dots are prepared by hydrothermal method, exhibit small size <10 nm, reveal significant quantum yield, biocompatibility, non-toxicity, photostability and display substantial tunable emission and can be efficiently employed for sensing, bioimaging and energy storage applications. Finally, the forthcoming challenges, investigations, and options open for the chemical and/or physical modification of lignin into fluorescent materials for future applications are well-addressed. To our knowledge, this is the first comprehensive review report on lignin-based fluorescent materials and their light-responsive applications. In addition, this review will attract remarkable consideration and thrust for the researchers and biochemical technologists working with the preparation of lignin-based fluorescent materials for broad applications.

Recent advances of sensing strategies for the detection of β-glucuronidase activity

β-Glucuronidase (β-GLU), a kind of hydrolase, is widely distributed in mammalian tissues, body fluids, and microbiota. Abnormal changes of β-GLU activity are often correlated with the occurrence of diseases and deterioration of water quality. Therefore, detection of β-GLU activity is of great significance in biomedicine and environmental health such as cancer diagnosis and water monitoring. However, the conventional β-GLU activity assay suffers from the limitations of low sensitivity, poor accuracy, and complex procedure. With the development of analytical chemistry, many advances have been made in the detection of β-GLU activity in recent years. The sensors for β-GLU activity detection which have the advantages of rapid and reliable detection have been attracting increased attentions. In this paper, the principles, performances, and limitations of these β-GLU sensors, including colorimetric sensing, fluorescent sensing, electrochemical sensing for the determination of β-GLU activity, have been summarized and discussed. Moreover, the challenges and research trends of β-GLU activity assay are proposed.

Tunable Light Emission from Lignin: Various Photoluminescence Properties Controlled by the Lignocellulosic Species, Extraction Method, Solvent, and Polymer

This report describes the tunable light emission from lignin, which was achieved by carefully selecting the lignocellulosic species, extraction method, solvent, and polymer. Lignins comprising various taxonomic species with distinct primary structures exhibited diverse photoluminescence (PL) intensities and spectral patterns. Investigations probing how the solvent affects the PL properties revealed that the PL quenching phenomenon originated from the decreasing distance between aromatic moieties (luminophores). Therefore, polymers can play key roles as media to modulate the distance between luminophores, and the PL intensity can be enhanced by employing a relatively stiff polymer. In terms of the emission color, the PL spectral pattern can be tuned by changing the lignin primary structures or by deprotonating the phenolic hydroxyl groups. By modulating these influencing factors, various light emissions were obtained from lignins in solutions and transparent solid materials.

Lignosulfonate/diblock copolymer polyion complexes with aggregation-enhanced and pH-switchable fluorescence for information storage and encryption

Employing natural polymers as building blocks is favorable to construct sustainable functional materials and realize biomass utilization. Here we developed a series of supramolecular polyion complexes (PICs) composed of lignosulfonate and double-hydrophilic diblock copolymer poly(ethylene oxide-b-N, N-dimethylaminoethyl methacrylate) (PEO₁₁₄-b-PDMAEMA₂₄), which performed a blue emission with quenching-enhancing tendency and copolymer distribution inversion-involved assembling transformation at pH 5.6 and monotonic greenish-blue fluorescence promotion at pH 9.5 by increasing PEO₁₁₄-b-PDMAEMA₂₄ contents. Electrostatic interactions and multiple hydrogen bonds were revealed controlled the assembling behavior and affected the emission via altering the restriction of molecular motion, through-space conjunction, and non-luminous complexation. The multiple interacting sites and special topology of diblock copolymer contributed to the efficient fluorescence regulation. Information writing-erasing and encryption-decryption systems were established by utilizing emission intensity regulation and pH-responsive emission chromism. This work paved a new way to enhance lignin fluorescence and broadened potential applications of lignin composites in realms of sensing, imaging, monitoring, and anticounterfeiting.

A ratiometric fluorescent sensor based on g-CNQDs@Zn-MOF for the sensitive detection of riboflavin via FRET

A novel ratiometric fluorescent sensor based on Förster resonance energy transfer (FRET) platform was designed for riboflavin (RF) detection. The graphitic carbon nitrides quantum dots - Zn-MOF composite (g-CNQDs@Zn-MOF) was used as the fluorescent probe. In the FRET system, g-CNQDs@Zn-MOF and RF acted as donor and acceptor, respectively. The probe exhibited high sensitivity and good selectivity to RF, and had been successfully used for the detection of RF in milk and vitamin B₂ tablets. The detection limit of the sensor was 15 nM. The strategy expanded the application of MOF in sensing filed and provided a new method for the detection of RF.