Lignin-AuNPs liquid marble for remotely-controllable detection of Pb2

Micro/nanoengineered agricultural by-products for biomedical and environmental applications

Agriculturally derived by-products generated during the growth cycles of living organisms as secondary products have attracted increasing interest due to their wide range of biomedical and environmental applications. These by-products are considered promising candidates because of their unique characteristics including chemical stability, profound biocompatibility and offering a green approach by producing the least impact on the environment. Recently, micro/nanoengineering based techniques play a significant role in upgrading their utility, by controlling their structural integrity and promoting their functions at a micro and nano scale. Specifically, they can be used for biomedical applications such as tissue regeneration, drug delivery, disease diagnosis, as well as environmental applications such as filtration, bioenergy production, and the detection of environmental pollutants. This review highlights the diverse role of micro/nano-engineering techniques when applied on agricultural by-products with intriguing properties and upscaling their wide range of applications across the biomedical and environmental fields. Finally, we outline the future prospects and remarkable potential that these agricultural by-products hold in establishing a new era in the realms of biomedical science and environmental research.

Highly sensitive detection of Pb2+ in the environment with DNAzyme and rolling circle amplification reaction

Lead (Pb2+) is a toxic heavy metal that can severely pollute the environment and cause harm to public health. Therefore, the prompt and accurate monitoring of lead levels in the environment is vital. In this study, a novel DNAzyme-based cascade signal amplification biosensor that could detect Pb2+ with high sensitivity was designed through the combination of the strand displacement reaction (SDR) and rolling circle amplification (RCA). When Pb2+ is absent, RCA is triggered under the synergistic action of T4 DNA ligase and phi29 DNA polymerase with an artificially fluorophore-labeled S-chains being released to replace the upstream products generated by repeated RCA, thereby restoring the quenched fluorescence and emitting a strong fluorescent signal. After adding Pb2+, 8-17 DNAzyme binds specifically to Pb2+ and catalyzes the cleavage of the rA site on a single-stranded DNA with artificially modified rA site to restrict the RCA. The designed sensor provides a linear detection range for Pb2+ from 25 pM to 1 µM, with a low limit of detection 8.3 pM. Significantly, this sensor still demonstrates satisfactory performance when used for detecting Pb2+ in environment samples (e.g., river water). We consider that our study can provide reference values and ideas for the development of heavy metal ion detection methods.

Fully Biobased Photothermal Films and Coatings for Indoor Ultraviolet Radiation and Heat Management

Sustainable materials are needed to mitigate against the increase in energy consumption resulting from population growth and urbanization. Here, we report fully biobased nanocomposite films and coatings that display efficient photothermal activity and selective absorption of ultraviolet (UV) radiation. The nanocomposites with 20 wt % of lignin nanoparticles (LNPs) embedded in a chitosan matrix displayed an efficient UV blocking of 97% at 400 nm along with solar energy-harvesting properties. The reflectance spectra of the nanocomposite films revealed the importance of well-dispersed nanoparticles in the matrix to achieve efficient UV-blocking properties. Finally, yet importantly, we demonstrate the nanocomposites with 20 wt % LNPs as photothermal glass coatings for passive cooling of indoor temperature by simply tailoring the coating thickness. Under simulated solar irradiation of 100 mW/cm², the 20 μm coating achieved a 58% decrease in the temperature increment in comparison to the system with uncoated glass. These renewable nanocomposite films and coatings are highly promising sustainable solutions to facilitate indoor thermal management and improve human health and well-being.

Electrospun polyacrylonitrile/hydroxyapatite composite nanofibrous membranes for the removal of lead ions from aqueous solutions

A novel Polyacrylonitrile/Hydroxyapatite (PAN/HAP) composite nanofibrous membranes were successfully prepared via the electrospinning approach. The scanning electron microscope, Fourier transforms infrared, X-ray diffraction were selected to serve as characterization techniques...

Lignin Biopolymer for the Synthesis of Iron Nanoparticles and the Composite Applied for the Removal of Methylene Blue

In the current study, lignin, an abundant natural polymer, was dissolved in ethylene glycol and acidic H2O to form nanoscale lignin. Then, zero-valent iron (ZVI) nanoparticles were synthesized in nanoscale lignin, producing a nZVI/n-lignin composite, via the borohydride reduction method. The use of nZVI/n-lignin for environmental remediation was tested by the removal of methylene blue in aqueous solutions at room temperature. The nZVI/n-lignin composite achieved a higher methylene blue removal ratio than that achieved by traditional nZVIs. Moreover, its excellent dispersibility in water and stability against oxidation in the air were observed. The functions of the nanoscale lignin in the composite material are (1) prevention of further growth and aggregation of the nZVI nanoparticles, (2) protection of nZVI from serious oxidation by H2O/O2, and (3) allowing better dispersibility of nZVI in aqueous solutions. These three functions are important for the field applications of nZVI/n-lignin, namely, to travel long distances before making contact with environmental pollutants. The present method for producing nZVI/n-lignin is straightforward, and the combination of nZVI and lignin is an efficient and environmentally friendly material for environmental applications.

Lignin-mediated green synthesis of functionalized gold nanoparticles via pulsed laser technique for selective colorimetric detection of lead ions in aqueous media

A versatile green synthesis technique of pulsed laser irradiation and the sonochemical process was used for the production of functionalized gold nanoparticles (Au NPs) in the presence of lignin matrixes. In this study, the futuristic advantages of the lignin biopolymer were explored for the preparation of zero-valent Au NPs in the absence of any other reducing agents. The resulting lignin functionalized Au NPs (L-Au_f NPs) were characterized via high-resolution transmission electron microscopy, X-ray diffraction, UV-vis spectroscopy, and Fourier-transform infrared spectroscopy. The optimum lignin concentration can generate uniformly dispersed crystalline L-Au_f NPs. The optimized L-Au_f (1-5) NPs permit the selective colorimetric detection of heavy metal ions; thus, the L-Au_f (1-5) NPs demonstrated a highly selective colorimetric sensing tendency toward Pb²⁺ ions within a short time interval among the various metal ions (Pb²⁺, Fe³⁺, Cu²⁺, Cr⁶⁺, Co²⁺, Ag²⁺, Ca²⁺, Cd²⁺, Ba²⁺, and Hg²⁺). The prominent color change of L-Au_f NPs from red wine to purple indicates the detection of Pb²⁺ ions. This robust characteristic nature of L-Au_f (1-5) NPs can also detect very low concentrations of 1.8 μM in the linear range of 0.1-1 mM. Hence, the outcome of this study coincides with existing studies and indicates that L-Au_f (1-5) NPs can also be used as effective sensors for the rapid and selective detection of Pb²⁺ ions via the colorimetric analysis using the real environmental samples.

Effect of UV Radiation on Optical Properties and Hardness of Transparent Wood

Optically transparent wood is a type of composite material, combining wood as a renewable resource with the optical and mechanical properties of synthetic polymers. During this study, the effect of monochromatic UV-C (λ—250 nm) radiation on transparent wood was evaluated. Samples of basswood were treated using a lignin modification method, to preserve most of the lignin, and subsequently impregnated with refractive-index-matched types of acrylic polymers (methyl methacrylate, 2-hydroxyethyl methacrylate). Optical (transmittance, colour) and mechanical (shore D hardness) properties were measured to describe the degradation process over 35 days. The transmittance of the samples was significantly decreased during the first seven days (12% EMA, 15% MMA). The average lightness of both materials decreased by 10% (EMA) and 17% (MMA), and the colour shifted towards a red and yellow area of CIE L*a*b* space coordinates. The influence of UV-C radiation on the hardness of the samples was statistically insignificant (W+MMA 84.98 ± 2.05; W+EMA 84.89 ± 2.46), therefore the hardness mainly depends on the hardness of used acrylic polymer. The obtained results can be used to assess the effect of disinfection of transparent wood surfaces with UV-C radiation (e.g., due to inactivation of SARS-CoV-2 virus) on the change of its aesthetic and mechanical properties.

Fabrication of magnetic polydopamine@naphthyl microporous organic network nanosphere for efficient extraction of hydroxylated polycyclic aromatic hydrocarbons and p-nitrophenol from wastewater samples

Herein, we report the fabrication of a novel, well-defined core-double-shell-structured magnetic Fe₃O₄@polydopamine@naphthyl microporous organic network (MON), Fe₃O₄@PDA@NMON, for the efficient magnetic extraction of hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and p-nitrophenol (p-Npn) from wastewater samples. The hierarchical nanospheres were designed and constructed with the Fe₃O₄ nanoparticle core, the inner shell of a polydopamine (PDA) layer, and the outer shell of a porous naphthyl MON (NMON) coating, allowing efficient and synergistic extraction of OH-PAHs and p-Npn via hydrophobic, hydrogen bonding, and π-π interactions. The Fe₃O₄@PDA@NMON nanospheres were well characterized and employed as an efficient sorbent for magnetic solid-phase extraction (MSPE) coupled with high performance liquid chromatography (HPLC) for analyzing of OH-PAHs and p-Npn. Under optimal conditions, the Fe₃O₄@PDA@NMON-based-MSPE-HPLC-UV method afforded wide linear range (0.18-500 μg L^-1), low limits of detection (0.070 μg L^-1 for p-Npn, 0.090 μg L^-1 for 2-OH-Nap, 0.090 μg L^-1 for 9-OH-Fluo and 0.055 μg L^-1 for 9-OH-Phe, respectively), large enrichment factors (92.6-98.4), good precisions (intra-day and inter-day relative standard deviations (RSDs); <6.4%, n=6) and less consumption of the adsorbent. Furthermore, trace OH-PAHs and p-Npn with concentrations of 0.29-0.80 μg L^-1 were successfully detected in various wastewater samples. Fe₃O₄@PDA@NMON also functioned as a good adsorbent to enrich a wide scope of trace contaminants containing hydrogen bonding sites and aromatic structures, highlighting the potential of functional MONs in sample pretreatment.

Liquid marble-based digital microfluidics - fundamentals and applications

Liquid marbles are droplets with volume typically on the order of microliters coated with hydrophobic powder. Their versatility, ease of use and low cost make liquid marbles an attractive platform for digital microfluidics. This paper provides the state of the art of discoveries in the physics of liquid marbles and their practical applications. The paper first discusses the fundamental properties of liquid marbles, followed by the summary of different techniques for the synthesis of liquid marbles. Next, manipulation techniques for handling liquid marbles are discussed. Applications of liquid marbles are categorised according to their use as chemical and biological reactors. The paper concludes with perspectives on the future development of liquid marble-based digital microfluidics.

In Situ Lignin Modification toward Photonic Wood

Lignin serves as a binder that forms strong matrices of the cell walls of wood. However, it has many photolabile chromophore groups that create a monotonic brownish color and make wood susceptible to photodegradation. Herein, a new strategy is reported for modifying lignin using an in situ, rapid, and scalable process that involves the photocatalytic oxidation of native lignin in wood by H₂ O₂ and UV light. The reaction selectively eliminates lignin's chromophores while leaving the aromatic skeleton intact, thus modulating the optical properties of wood. The resulting "photonic wood" retains ≈80% of its original lignin content, which continues to serve as a strong binder and water-proofing agent. As a result, photonic wood features a much higher mechanical strength in a wet environment (20-times higher tensile strength and 12-times greater compression resistance), significant scalability (≈2 m long sample), and largely reduced processing times (1-6.5 h vs 4-14 h) compared with delignification methods. Additionally, this in situ lignin-modified wood structure is easily patterned through a photocatalytic oxidation process. This photocatalytic production of photonic wood paves the way for the large-scale manufacturing of sustainable biosourced functional materials for a range of applications, including energy-efficient buildings, optical management, and fluidic, ionic, electronic, and optical devices.

Eco-friendly synthesis of lignin mediated silver nanoparticles as a selective sensor and their catalytic removal of aromatic toxic nitro compounds

The development of an eco-friendly and reliable process for the production of nanomaterials is essential to overcome the toxicity and exorbitant cost of conventional methods. As such, a facile and green synthesis method is introduced for the preparation of lignin mediated silver nanoparticles (L-Ag NPs). This is produced by reducing Ag precursors using lignin biopolymers which are formulated by pulsed laser irradiation and an ultrasonication process. Lignin operates as both a reducing and stabilizing agent. The various analytical techniques of ultraviolet-visible spectroscopy, transmission electron microscope and X-ray diffractometer studies were employed to verify the formation of non-aggregated spherical L-Ag NPs with an average size as small as 7-8 nm. The selective sensing capability of the synthesized L-Ag NPs was examined for the detection of hydrogen peroxide and mercury ions in an aqueous environment. Furthermore, the superior catalytic performance of L-Ag NPs was demonstrated by the rapid conversion of toxic 4-nitrophenol and nitrobenzene as targeted pollutants to the corresponding amino compounds. A plausible catalytic reduction mechanism for the removal of toxic nitro-organic pollutants over L-Ag NPs is proposed. This research coincides with existing studies and affirms that L-Ag NPs are an effective sensor that be applied as a catalytic material within environmental remediation and also alternative biomedical applications.

Green Synthesis and Characterization of Gold Nanoparticles Using Lignin Nanoparticles

With the development of nanotechnology, gold nanoparticles (Au NPs) have attracted enormous attention due to their special properties. The green synthesis of Au NPs from lignin would inspire the utilization of lignin and its related functional materials. In this study, a rapid preparation process of Au NPs was investigated by utilizing lignin nanoparticles (LNPs) under room temperature without chemical addition. The LNPs acted as a reducing agent, stabilizing agent, and template for the preparation of LNPs@AuNPs. The obtained LNPs@AuNPs were characterized by UV-Vis spectrum, Transmission Electron Microscope (TEM), and X-ray photoelectron spectroscopy (XPS). The possible mechanism was illustrated by Fourier Transform Infrared Spectroscopy (FT-IR), ³¹P, XPS, and UV analyses. The abundant hydroxyl groups (24.96 mmol/g) favored the preparation of Au NPs. Au NPs diameters of 10–30 nm were well dispersed in the LNPs. The optimal reaction conditions were a ratio of 10 mg of LNPs to 0.05 mmol HAuCl₄, room temperature, and a reaction time of 30 min. The LNPs@AuNPs exhibited excellent stability in the suspension for more than seven days. The reduction process could be related to the disruption of side chains of lignin, hydroxyl group oxidation, and hydroquinones and quinones from the comproportionation reaction. The LNPs@AuNPs would open a door for the design of Au NP/lignin-derived novel functional materials.

"Waste to Wealth": Lignin as a Renewable Building Block for Energy Harvesting/Storage and Environmental Remediation

Lignin is the second most earth-abundant biopolymer having aromatic unit structures, but it has received less attention than other natural biomaterials. Recent advances in the development of lignin-based materials, such as mesoporous carbon, flexible thin films, and fiber matrix, have found their way into applications to photovoltaic devices, energy-storage systems, mechanical energy harvesters, and catalytic components. In this Review, we summarize and suggest another dimension of lignin valorization as a building block for the synthesis of functional materials in the fields of energy and environmental applications. We cover lignin-based materials in the photovoltaic and artificial photosynthesis for solar energy conversion applications. The most recent technological evolution in lignin-based triboelectric nanogenerators is summarized from its fundamental properties to practical implementations. Lignin-derived catalysts for solar-to-heat conversion and oxygen reduction are discussed. For energy-storage applications, we describe the utilization of lignin-based materials in lithium-ion rechargeable batteries and supercapacitors (e.g., electrodes, binders, and separators). We also summarize the use of lignin-based materials as heavy-metal adsorbents for environmental remediation. This Review paves the way to future potentials and opportunities of lignin as a renewable material for energy and environmental applications.

Fabrication of gold-silver core-shell nanoparticles for performing as ultrabright SERS-nanotags inside human ovarian cancer cells

This paper presents the fabrication and characterization of new gold-silver core-shell nanoparticles labeled with para-mercaptobenzoic acid (4MBA) molecules and demonstrates their use as surface-enhanced Raman spectroscopy (SERS)-nanotags with ultra-bright traceability inside cells and ability to convey spectrally-coded information about the intracellular pH by means of SERS. Unlike previous reported studies, our fabrication procedure includes in the first step the synthesis of chitosan-coated gold nanoparticles as a seed material with subsequent growing of a silver shell. The bimetallic core-shell structure is revealed by transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, energy-dispersive x-ray elemental mapping and the presence of two interacting localized surface plasmon resonance modes in UV-vis extinction spectrum. The high SERS activity and sensitivity of as fabricated 4MBA-chit-Au-AgNPs nano-constructs to different pH in solution is investigated under 532 and 633 nm laser lines excitation. Next, in view of future studies in cancer diagnosis, the in vitro antiproliferative effects of SERS-nanotags against human ovarian adenocarcinoma cells (NIH:OVCAR-3) are evaluated. The capacity to operate as bright SERS nanotags with precise localization at a single cell level as well as intracellular pH indicators is clearly demonstrated by performing cell imaging under scanning confocal Raman microscopy.

Engineering Lignin Stabilized Bimetallic Nanocomplexes: Structure, Mechanistic Elucidation, Antioxidant, and Antimicrobial Potential

Lignin, being a natural antioxidant and antimicrobial underutilized biopolymer derived mainly from agro-waste, is a material of great interest. In this study, lignin was chosen as a matrix to synthesize silver-gold bimetallic and monometallic nanocomplexes to explore the synergistic antioxidant and antimicrobial properties of the lignin stabilized nanoagents. The synthesis of the nanocomplexes was carried out using a one pot method, utilizing lignin as the sole source for reducing, capping, and stabilizing the nanoagents. Further, characterization studies were performed to determine the exact structure of the nanocomplexes. The developed nanocomplexes were found to possess substantial phenolic and flavonoid contents, which contributed to their high antioxidant activity. Further, the antioxidant and antimicrobial activity of the lignin-bimetallic and monometallic nanocomplexes was evaluated and compared with pristine lignin. Moreover, the mechanism behind the antimicrobial activity of the nanocomplexes was elucidated through various methods, namely, reactive oxygen generation, nucleic acid leakage, and DNA cleavage studies. The obtained results were greatly supported by scanning electron microscopy, transmission electron microscopy, and live-dead cell imaging techniques. This study is a contribution in converting waste to value added functional nanomaterials for potential antioxidant and antimicrobial applications.

Effect of synthesis, purification and growth determination methods on the antibacterial and antifungal activity of gold nanoparticles

In recent years, both nanotechnology and the use of nanomaterials have been growing in fields as diverse as biomedicine, food or electronics. Particularly metal nanoparticles, such as gold nanoparticles (AuNPs), are being widely studied with different applications, for example as an antimicrobial agent, in hyperthermic therapy or drug transport. Gold nanoparticles can be synthesized by different methods, such as stand out reduction with citrate or greener methods that use greener reducing agents (e.g. stainless steel). In the present work, both the effect of the synthesis method yielding AuNPs with similar size and purification of AuNPs affect the antibacterial and antifungal activities of the AuNPs obtained by citrate reduction and with stainless steel. The growth curves of the gram-negative (E. coli) and gram-positive bacteria (S. aureus) and the yeast C. albicans were constructed and the cell viability was evaluated by (2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT). According to our results, the purification of the AuNPs after their synthesis and the growth determination method affect the antibacterial and antifungal activities while the synthesis method shows no significant differences.

Fabrication of Pd NPs-supported porous carbon by integrating the reducing reactivity and carbon-rich network of lignin

The renewable resource as a major feedstock to prepare porous carbon has showed many advantages compared to fossil-based materials. This study proposes a new strategy to synthesize palladium nanoparticles (Pd NPs)-supported porous carbon, utilizing both the chemical reactivity and the carbon-rich 3D network of lignin. The Pd NPs-supported porous carbons were prepared in one-pot synthesis, with Pd(NH3)2Cl2 as precursor, lignin as reducing and stabilizing agents of Pd NPs, nano SiO2 as hard-template, followed by carbonization and removal of the template. The results reveal a positive effect of Pd precursor dosage on the development and excellent texture of the Pd NPs-supported porous carbon. Accordingly, the synthesized porous carbon was proved to have large micropore volume and good micro-mesopore porous structure, revealing it a promising hydrogen adsorbent.

Biopolymer as Stabilizer and Adhesive To in Situ Precipitate CuS Nanocrystals on Cellulose Nanofibers for Preparing Multifunctional Composite Papers

In order to solve the uneven distribution of copper sulfide nanocrystals (CuS-NCs) on cellulose nanofibers (CNFs), this work reports a feasible method to in situ precipitate CuS-NCs on CNF by utilizing biopolymers (lignin, xylan, or starch) as stabilizer and adhesive for fabricating the multifunctional composite papers. In the presence of biopolymers, CuS-NCs deposited in situ on CNF could be capped and stabilized by the biopolymers molecular chains for uniform distribution. Subsequently, biopolymers could anchor CuS-NCs on CNF by the hydrogen bonding. Compared to the composite paper with lignin or xylan as stabilizer and adhesive, CuS-NCs/starch/CNF paper showed the highest content and most uniform and continuous distribution of CuS-NCs, which not only enhanced the conductivity of composite paper to 10.12 S/cm but also increased the reaction rate constant on photocatalytic degradation of rhodamine B to 0.317 min-1. The reaction rate constant is higher than most of the other reported CuS photocatalysts to date. It indicates that our method has a potential to be a novel strategy to precipitate nanocrystals uniformly on cellulose fibers for fabricating the multifunctional composite paper.