Paper surfaces functionalized by nanoparticles

Near-infrared downshifting luminescence of Ca2LaTaO6:Nd3+/Yb3+/K+ phosphors and their applications: solar cells and anti-counterfeiting

A series of Nd3+/Yb3+ co-doped Ca2LaTaO6 (CLTO) phosphors are synthesized by a high temperature solid phase method. Structural characterization confirms the successful incorporation of Nd3+ and Yb3+ ions into the CLTO host lattice. The photoluminescence excitation (PLE) spectra and photoluminescence (PL) spectra of CLTO:Nd3+ and CLTO:Nd3+/Yb3+ are investigated in detail. Under the excitation of ultraviolet (UV) and visible (VIS) light, the CLTO:Nd3+/Yb3+ phosphor emits broadband near infrared (NIR) luminescence. In particular, the luminescence intensity of the Yb3+ ion is increased through an energy transfer (ET) process from Nd3+ to Yb3+. The luminescence mechanism of the CLTO:Nd3+/Yb3+ sample is analyzed based on the decay lifetime and PL spectra. In addition, the NIR emission intensity of Yb3+ ions is also enhanced by doping K+ ions. The broadband luminescence (850-1050 nm) of the CLTO:Nd3+/Yb3+/K+ phosphor has good application in solar cells and anti-counterfeiting.

Single-Domain Antibody-Gold Nanoparticle Bioconjugates as Immunosensors for the Detection of Hantaviruses

INTRODUCTION

Hantavirus, a zoonotic pathogen, causes severe syndromes like hemorrhagic fever with renal syndrome (HFRS), sometimes fatal in humans. Considering the importance of detecting the hantavirus antigen, the construction of an immunosensor is essential. The structural and functional characteristics of camelid nanobodies (VHHs) encourage their application in the areas of nanobiotechnology, therapeutics, diagnostics, and basic research. Therefore, this study aimed to standardize stable bioconjugates using gold nanoparticles (AuNPs) and VHHs, in order to develop immunobiosensors for the diagnosis of hantavirus infection.

METHODS

Immobilized metal affinity chromatography (IMAC) was performed to obtain purified recombinant anti-hantavirus nucleocapsid nanobodies (anti-prNΔ85 VHH), while AuNPs were synthesized for bioconjugation. UV-visible spectrophotometry and transmission electron microscopy (TEM) analysis were employed to characterize AuNPs.

RESULTS

The bioconjugation stability parameters (VHH-AuNPs), analyzed by spectrophotometry, showed that the ideal pH value and VHH concentration were obtained at 7.4 and 50 μg/mL, respectively, after addition of 1 M NaCl, which induces AuNP aggregation. TEM performed before and after bioconjugation showed uniform, homogeneous, well-dispersed, and spherical AuNPs with an average diameter of ~ 14 ± 0.57 nm. Furthermore, high-resolution images revealed a thin white halo on the surface of the AuNPs, indicating the coating of the AuNPs with protein. A biosensor simulation test (dot blot-like [DB-like]) was performed in stationary phase to verify the binding and detection limits of the recombinant nucleocapsid protein from the Araucária hantavirus strain (prN∆85).

DISCUSSION

Using AuNPs/VHH bioconjugates, a specific interaction was detected between 5 and 10 min of reaction in a dose-dependent manner. It was observed that this test was sensitive enough to detect prNΔ85 at concentrations up to 25 ng/μL. Considering that nanostructured biological systems such as antibodies conjugated with AuNPs are useful tools for the development of chemical and biological sensors, the stability of the bioconjugate indicates proficiency in detecting antigens. The experimental results obtained will be used in a future immunospot assay or lateral flow immunochromatography analysis for hantavirus detection.

Phasor-FLIM analysis of cellulose paper ageing mechanism with carbotrace 680 dye

Ageing of paper is a complex process of great relevance for application purposes because of its widespread use as support for information storage in books and documents, and as common low-cost and green packaging material, to name a few. A key factor in paper ageing is the oxidation of cellulose, a macromolecule of natural origin that constitutes the main chemical component of paper. Such a complex process results in changes in the cellulose polymeric chains in chemical and structural properties. The scope of this work is to explore the effects of oxidation of cellulose as one of the principal mechanisms of ageing of paper using a fluorescence-based approach. To this aim, fluorescence-lifetime imaging microscopy (FLIM) measurements on pure cellulose samples stained using Carbotrace 680 dye were performed, and data were analyzed by phasor approach. The comparison with results from conventional techniques allowed to map paper microstructure as a function of the sample oxidation degree correlating the fluorescence-lifetime changes to cellulose oxidation. A two-step oxidation kinetics that produced specific modification in paper organization was highlighted indicating that FLIM measurements using Carbotrace 680 dye may provide a simple tool to obtain information on the oxidation process also adding spatial information at sub-micrometric scale.

Optimization of a silver-nanoprism conjugated with 3,3',5,5'-tetramethylbenzidine towards easy-to-make colorimetric analysis of acetaldehyde: a new platform towards rapid analysis of carcinogenic agents and environmental technology

Acetaldehyde acts as an important mediator in the metabolism of plants and animals; however, its abnormal level can cause problems in biological processes. Although acetaldehyde is found naturally in many organisms, exposure to high concentrations can have effects on the eyes, respiratory system, etc. Due to the importance of detecting acetaldehyde in environmental samples and biofluids, determination of its concentration is highly demanded. There are some reports showing exposure to high concentrations of acetaldehyde for a long time can increase the risk of cancer by reacting with DNA. In this work, we presented a novel colorimetric method for rapid and sensitive detection of acetaldehyde with high reproducibility using different AgNPs with various morphologies. The redox reaction between AgNPs, 3,3',5,5'-tetramethylbenzidine (TMB) solution, and analytes endows a color change in 15 minutes that is detectable by the naked eye. UV spectrophotometry was further used for quantitative analysis. An iron mold with a hexagonal pattern and liquid paraffin were also used to prepare the paper-based microfluidic substrate, as a low cost, accessible, and rapid detection tool. Different types of AgNPs showed different lower limits of quantification (LLOQ). The AgNPs-Cit and AgNPrs could identify acetaldehyde with linear range of 10-7 to 10 M and an LLOQ of 10-7 M. The AgNWs showed the best color change activity with a linear range 10-5 to 10 M and the lowest diagnostic limit is 10-5 M. Finally, analysis of human biofluids as real samples were successfully performed using this system.

Colorimetric and naked-eye detection of arsenic(iii) using a paper-based microfluidic device decorated with silver nanoparticles

Arsenic (As) as a metal ion has long-term toxicity and its presence in water poses a serious threat to the environment and human health. So, rapid and accurate recognition of traces of As is of particular importance in environmental and natural resources. In this study, a fast and sensitive colorimetric method was developed using silver nano prisms (Ag NPrs), cysteine-capped Ag NPrs, and methionine-capped Ag NPrs for accurate detection of arsenic-based on transforming the morphology of silver nanoparticles (AgNPs). The generated Ag atoms from the redox reaction of silver nitrate and As(iii) were deposited on the surface of Ag NPrs and their morphology changed to a circle. The morphological changes resulted in a change in the color of the nanoparticles from blue to purple, which was detectable by the naked eye. The rate of change was proportional to the concentration of arsenic. The changes were also confirmed using UV-Vis absorption spectra and showed a linear relationship between the change in adsorption peak and the concentration of arsenic in the range of 0.0005 to 1 ppm with a lower limit of quantification (LLOQ) of 0.0005 ppm. The proposed probes were successfully used to determine the amount of As(iii) in human urine samples. In addition, modified microfluidic substrates were fabricated with Ag NPrs, Cys-capped Ag NPrs, and methionine-capped Ag NPrs nanoparticles that are capable of arsenic detection in the long-time and can be used in the development of on-site As(iii) detection kits. In addition, silver nanowires (AgNWs) were used as a probe to detect arsenic, but good results were not obtained in human urine specimens and paper microfluidic platforms. In this study, for the first time, AgNPs were developed for optical colorimetric detection of arsenic using paper-based microfluidics. Ag NPrs performed best in both optical and colorimetric techniques. Therefore, they can be a promising option for the development of sensitive, inexpensive, and portable tools in the environmental and biomedical diagnosis of As(iii).

Nanomaterials-based drug delivery approaches for wound healing

Abstract:

Wound healing is a complex and dynamic process that requires intricate synchronization between multiple cell types within appropriate extracellular microenvironment. Wound healing process involves four overlapping phases in a precisely regulated manner, consisting of hemostasis, inflammation, proliferation, and maturation. For an effective wound healing all four phases must follow in a sequential pattern within a time frame. Several factors might interfere with one or more of these phases in healing process, thus causing improper or impaired wound healing resulting in non-healing chronic wounds. The complications associated with chronic non-healing wounds, along with the limitations of existing wound therapies, have led to the development and emergence of novel and innovative therapeutic interventions. Nanotechnology presents unique and alternative approaches to accelerate the healing of chronic wounds by the interaction of nanomaterials during different phases of wound healing. This review focuses on recent innovative nanotechnology-based strategies for wound healing and tissue regeneration based on nanomaterials, including nanoparticles, nanocomposites and scaffolds. The efficacy of the intrinsic therapeutic potential of nanomaterials (including silver, gold, zinc oxide, copper, cerium oxide, etc.) and the ability of nanomaterials as carriers (liposomes, hydrogels, polymeric nanomaterials, nanofibers) as therapeutic agents associated with wound-healing applications have also been addressed. The significance of these nanomaterial-based therapeutic interventions for wound healing needs to be highlighted to engage researchers and clinicians towards this new and exciting area of bio-nanoscience. We believe that these recent developments will offer researchers an updated source on the use of nanomaterials as an advanced approach to improve wound healing.

Nanomaterial-Based Therapy for Wound Healing

Poor wound healing affects millions of people globally, resulting in increased mortality rates and associated expenses. The three major complications associated with wounds are: (i) the lack of an appropriate environment to enable the cell migration, proliferation, and angiogenesis; (ii) the microbial infection; (iii) unstable and protracted inflammation. Unfortunately, existing therapeutic methods have not solved these primary problems completely, and, thus, they have an inadequate medical accomplishment. Over the years, the integration of the remarkable properties of nanomaterials into wound healing has produced significant results. Nanomaterials can stimulate numerous cellular and molecular processes that aid in the wound microenvironment via antimicrobial, anti-inflammatory, and angiogenic effects, possibly changing the milieu from nonhealing to healing. The present article highlights the mechanism and pathophysiology of wound healing. Further, it discusses the current findings concerning the prospects and challenges of nanomaterial usage in the management of chronic wounds.

Hybrid attention network with appraiser-guided loss for counterfeit luxury handbag detection

Recently, convolutional neural networks have shown good performance in many counterfeit detection tasks. However, accurate counterfeit detection is still challenging due to the following three issues: (1) fine-grained classification, (2) class imbalance, and (3) high imitation samples. To address these issues, we propose a hybrid attention network (HANet) for counterfeit luxury handbag detection. In HANet, a hybrid attention module is first designed. Compared with existing methods that directly use classic CNNs for counterfeit detection, the HA module jointly uses a channel attention unit and a spatial attention unit to learn important information on both the channel and spatial dimensions. The HA modules can be easily integrated into the ResNet architecture to enhance the discriminative representation ability of CNNs, so as to help the network find subtle differences between the real and counterfeit products. In addition, an appraiser-guided loss is proposed to train HANet. Considering the factor of class imbalance and high imitation samples, the proposed loss gives the counterfeit class a higher weighting, and meanwhile gives the high imitation samples a much higher weighting. The proposed loss introduces the knowledge of appraisers, which allows HANet to not only treat real and counterfeit samples relatively fairly, but also pay more attention to the learning of difficult samples. To evaluate the performance of our method, we have constructed a well-benchmarked luxury handbag dataset. On this dataset, the performance of HANet, ResNet50, and the state-of-the-art attention methods is compared. The results demonstrate that HANet achieve superior performance against all its competitors.

Paper-based field-effect transistor sensors

The present scenario in the world largely demands affordable, fast, recyclable, and flexible electronic devices for bio sensing. Varieties of paper-based devices such as microfluidics paper electrodes, paper diodes, and paper-based transistors etc. have been developed and validated. Most of the fabrication techniques published so far have focused on economic, environment-friendly straightforward methods to develop paper-based field-effect transistors (PFET) sensors, additionally, explored their applications. The synthetic-free, mechanically flexible, biocompatible, and signal amplification capability render PFET based sensors for wearable device makers. Modified organic/inorganic PFETs identify target analytes based on the electrical signal and endow them as perfect transducers. In the field of PFET bio sensing technology, numerous challenges are needed to be discussed to proceed forward in biomedical and other analytical applications. Realizing biologically or chemically modified PFET having an exceptional signal to noise ratio, specificity, with rapid detection ability is challenging. This review recapitulates the fabrication techniques, performances of various PFET sensors, and summarizes the report by concluding remarks including the limitations of the existing PFET based sensors and the future holds in regards to the sustainable nature of PFET.

Flexible SERS platform based on Ti3C2Tx-modified filter paper: preparation and SERS application

A novel, simple, and inexpensive flexible surface-enhanced Raman-scattering (SERS) platform based on common laboratory filter paper modified with Ti₃C₂T_x flakes was reported. Ti₃C₂T_x synthesized from a Ti₃AlC₂ phase with a mixture of HCl and LiF and Ti₃C₂T_x nanosheets were characterized by the TEM, XRD, UV-Vis spectrum, and Raman spectrum. Paper-based substrate has been proven to sample on rough and irregular surfaces. Thus, Ti₃C₂T_x was further manufactured as paper substrate by the immersion method to transfer nanosheets to filter paper. SERS activity of prepared substrate was demonstrated using R6G by the same filter paper modified with and without Ti₃C₂T_x, and various concentrations of R6G were tested to prove the sensitivity of the substrates. Further detection of CV and MG certified the universality of paper substrate based on Ti₃C₂T_x nanosheets for detection of organic pollutants. The uniformity and stability were proved by CV and R6G molecules. This SERS platform combines the advantages of 2D material and flexible paper scaffolds, resulting in a highly sensitive, cost-efficient, and easy-to-manufacture large-scale flexible substrate and is expected to be used in practice.

Paper Functionalized with Nanostructured TiO2/AgBr: Photocatalytic Degradation of 2-Propanol under Solar Light Irradiation and Antibacterial Activity

A facile method to produce paper–TiO₂ decorated with AgBr nanoparticles by a mild hydrothermal process at 140 °C was reported. The synthesis method was based on the immersion of the paper in a ready-made suspension of TiO₂/AgBr, comprising TiO₂ sol solution prepared in acidic conditions and AgBr solution (10⁻⁴ M). A paper–TiO₂ sample was prepared and used as reference. The formation of crystalline phases of titanium oxide (TiO₂) and silver bromide (AgBr) was demonstrated by XRD, Raman and EDX analyses. The surface morphology of the TiO₂–AgBr was investigated by Field Effect Scanning Electronic Microscopy (FE–SEM). The photocatalytic performances of the prepared material were evaluated in the degradation of 2-propanol in the gas phase, under simulated sunlight illumination. Its antibacterial properties against Escherichia coli (E. coli) were also assessed. The efficiency of photodegradation and the anti-bacterial properties of paper–TiO₂–AgBr were attributed to an improvement in the absorption of visible light, the increased production of reactive oxygen species (ROS) and the low recombination of photogenerated charge carriers due to the synergistic effect between TiO₂ and AgBr/Ag nanoparticles.

Dielectric nanosheet modified plasmonic-paper as highly sensitive and stable SERS substrate and its application for pesticides detection

The interaction of plasmonic nanoparticles with a dielectric platform gives rise to unique optical behaviors and this can be maneuvered to improve the plasmonic/SERS performances of a substrate. Herein, dielectric modified plasmonic-paper SERS substrate is developed by assembling Ag@SiO₂ nanocubes on Fe-TiO₂ nanosheets (NS) modified paper. The Fe-TiO₂ NS being visible light responsive significantly alters the optical property of the paper and serves as a dielectric underlay for the Ag nanocubes. Hence, the incident light reflected back from the dielectric nanosheets couples with the scattered light from the Ag nanocubes leading to spatially enhanced electromagnetic field improving the SERS enhancement. The prepared dielectric modified plasmonic-paper has an average enhancement factor (EF) of 1.49 × 10⁷ using R6G as a probe molecule. This value is superior to unmodified plasmonic-paper highlighting the coupling effect of the dielectric nanosheets. The substrate shows robust detection performance for thiabendazole and achieves a limit of detection (LOD) of 19 μg/L, which is 4-fold more sensitive than unmodified plasmonic paper. Direct swabbing test of thiabendazole sprayed apple fruit shows a discernible Raman signal down to 15 ppb indicating the utility of the substrate for point-of-need applications in food safety.

Lock Stock and Barrel of Wound Healing

Any kind of injury may lead to wound formation. As per World Health Organization Report, "more than 5 million people die each year due to injuries. This accounts for 9% of the world's population death, nearly 1.7 times the number of fatalities that result from HIV/AIDS, tuberculosis and malaria combined. In addition, ten million people suffer from non-fatal injuries which require treatment". This scenario leads to increased health and economic burden worldwide. Rapid wound healing is exigent subject-field in the health care system. It is imperative to be updated on wound care strategies as impaired wound healing may lead to chronic, non-healing wounds and thus further contributes to the national burden. This article is a comprehensive review of wound care strategies. The first and second part of this review article focuses on the understanding of wound, its types and human body's healing mechanism. Wound healing is natural, highly coordinated process that starts on its own, immediately after the injury. However, individual health condition influences the healing process. Discussion of factors affecting wound healing has also been included. Next part includes the detailed review of diverse wound healing strategies that have already been developed for different types of wound. A detailed description of various polymers that may be used has been discussed. Amongst drug delivery systems, oligomers, dendrimers, films, gels, different nano-formulations, like nanocomposites, nanofibers, nanoemulsions and nanoparticles are discussed. Emphasis on bandages has been made in this article.

Deposition of CdTe quantum dots on microfluidic paper chips for rapid fluorescence detection of pesticide 2,4-D

Rapid detection of pesticides in fruits is an ongoing challenge. The objective of the present study was to develop novel fluorescent microfluidic paper chips for specific recognition and sensitive detection of the pesticide 2,4-D through the electron-transfer-induced fluorescence quenching mechanism. CdTe quantum dots (QDs) were deposited onto cellulose paper (base material) to yield imprinted paper chips (paper@QDs@MIPs). This method allows the transferability of the molecularly imprinted fluorescence sensor from the liquid phase to the solid phase (paper base) for rapid and portable analysis. The resultant imprinted paper chips were effectively characterized, and they exhibited ideal ordered spatial network structure, chemical stability, and fluorescence property. The paper@QDs@MIPs showed that 2,4-D binding significantly reduced the fluorescence intensity within less than 18 min, and it achieved satisfactory linearity in the range of 0.83-100 μM and high detectability of 90 nM. The recognition specificity for 2,4-D relative to its analogues was shown, and the imprinting factor was 2.13. In addition, the recoveries of the spiked bean sprouts at three concentration levels ranged within 94.2-107.0%, with a relative standard deviation of less than 5.9%. Collectively, the device provided an effective platform for rapid recognition, convenience, and detection of trace food pollutants in complex matrices, thereby ensuring food safety and further promoting surface imprinting studies.

Surface-Enhanced Raman Spectroscopy (SERS) of Mancozeb and Thiamethoxam Assisted by Gold and Silver Nanostructures Produced by Laser Techniques on Paper

Advanced gold (Au) and silver (Ag) nanostructures were produced by laser techniques on printer paper substrate. Surface-enhanced Raman spectroscopy (SERS) analyses of the fungicide mancozeb (Dithane DG) and insecticide thiamethoxam (Aktara 25 BG) in quantities smaller than usually applied in agricultural medicine were performed for the first time assisted by the structures fabricated. The investigations and results show an easy alternative and cheap way to detect small amounts or residue of harmful environmental pollutants, which has a direct bearing on food quality and thus on human health.

Deactivation of E. coli in water using Fe3+-saturated montmorillonite impregnated filter paper

In areas with high exposure to pathogen contaminated water and lack the economic means for water treatment, low cost and convenient point-of-use drinking water disinfection materials/devices are essential. Using a simple craft paper making method, Fe³⁺-saturated montmorillonite impregnated filter paper was constructed to filter live Escherichia coli (E. coli)-spiked water. The Scanning Electron Microscopic images of the E. coli cells in contact with the Fe³⁺-saturated montmorillonite impregnated filter paper showed: 1) Fe³⁺-saturated montmorillonite particles were uniformly coated on the cellulose paper fiber, creating large mineral surface for cell contact; and 2) E. coli cell membrane was dehydrated and damaged, resulting cell deactivation upon contacting with the Fe³⁺-saturated montmorillonite particles impregnated in the paper. The E. coli cells passing through the Fe³⁺-saturated montmorillonite impregnated filter paper were not viable as further confirmed by the microfluidic dielectrophoresis analysis. They remained non-viable at room temperature even after 5 days, as shown by the results from both the Colony Counting test and the Colilert test. More than 99.5% deactivation efficiency was achieved when the ratio of the volume of the E. coli contaminated water to the mass of Fe³⁺-saturated montmorillonite was maintained at <1:1.5 (mL/mg). The Fe³⁺-saturated montmorillonite impregnated filter paper maintained ~74% E. coli deactivation efficiency even after the 8th consecutive use. About 0.52 mg Fe³⁺, which is bioavailable, could be leached into the water for every 2 L E coli-contaminated water that is treated with the filter paper. The treated water could therefore provide iron supplement to a person at a level within the range of the FDA recommended human daily intake of iron. The results from this study has clearly demonstrated promising potential of using the Fe³⁺-saturated montmorillonite impregnated filter paper for low cost (~$0.07/L treated water for this study) and convenient point-of-use drinking water disinfection.

Illuminating the Anticancerous Efficacy of a New Fungal Chassis for Silver Nanoparticle Synthesis

Biogenic silver nanoparticles (Ag NPs) have supple platforms designed for biomedical and therapeutic intervention. Utilization of Ag NPs are preferred in the field of biomedicines and material science research because of their antioxidant, antimicrobial, and anticancerous activity along with their eco-friendly, biocompatible, and cost-effective nature. Here we present a novel fungus Piriformospora indica as an excellent source for obtaining facile and reliable Ag NPs with a high degree of consistent morphology. We demonstrated their cytotoxic property, coupled with their intrinsic characteristic that make these biogenic nanoparticles suitable for the anticancerous activity. In vitro cytotoxicity of biologically synthesized Ag NPs (BSNPs) and chemically synthesized Ag NPs (SNPs) was screened on various cancer cell lines, such as Human breast adenocarcinoma (MCF-7), Human cervical carcinoma (HeLa), Human liver hepatocellular carcinoma (HepG2) cell lines and embryonic kidney cell line (HEK-293) as normal cell lines. The antiproliferative outcome revealed that the BSNPs exhibited significant cytotoxic activity against MCF-7 followed by HeLa and HepG2 cell lines as compared to SNPs. The blend of cytotoxic properties, together with green and cost-effective characteristics make up these biogenic nanoparticles for their potential applications in cancer nanomedicine and fabrication coating of ambulatory and non-ambulatory medical devices.

Environmentally friendly covalent coupling of proteins onto oxidized cellulosic materials

Cellulose is a biodegradable and renewable material that is one of the most abundant biopolymers with many different applications from low value newsprint products to high value biomedical sensor devices.

Enhancement of local surface plasmon resonance (LSPR) effect by biocompatible metal clustering based on ZnO nanorods in Raman measurements

The development of size-selective and non-destructive detection techniques for nanosized biomarkers has many reasons, including the study of living cells and diagnostic applications. We present an approach for Raman signal enhancement on biocompatible sensing chips based on surface enhancement Raman spectroscopy (SERS). A sensing chip was fabricated by forming a ZnO-based nanorod structure so that the Raman enhancement occurred at a gap of several tens to several hundred nanometers. The effect of coffee-ring formation was eliminated by introducing the porous ZnO nanorods for the bio-liquid sample. A peculiarity of this approach is that the gold sputtered on the ZnO nanorods initially grows at their heads forming clusters, as confirmed by secondary electron microscopy. This clustering was verified by finite element analysis to be the main factor for enhancement of local surface plasmon resonance (LSPR). This clustering property and the ability to adjust the size of the nanorods enabled the signal acquisition points to be refined using confocal based Raman spectroscopy, which could be applied directly to the sensor chip based on the optimization process in this experiment. It was demonstrated by using common cancer cell lines that cell growth was high on these gold-clad ZnO nanorod-based surface-enhanced Raman substrates. The porosity of the sensing chip, the improved structure for signal enhancement, and the cell assay make these gold-coated ZnO nanorods substrates promising biosensing chips with excellent potential for detecting nanometric biomarkers secreted by cells.

Luminescent-Magnetic Cellulose Fibers, Modified with Lanthanide-Doped Core/Shell Nanostructures

Novel luminescent-magnetic cellulose microfibers were prepared by a dry-wet spinning method with the use of N-methylmorpholine-N-oxide. The synthesized luminescent-magnetic core/shell type nanostructures, based on the lanthanide-doped fluorides and magnetite nanoparticles (NPs)-Fe₃O₄/SiO₂/NH₂/PAA/LnF₃, were used as nanomodifiers of the fibers. Thanks to the successful incorporation of the bifunctional nanomodifiers into the cellulose structure, the functionalized fibers exhibited superior properties, that is, bright multicolor emission under UV light and strong magnetic response. By the use of the as-prepared fibers, the luminescent-magnetic thread was fabricated and used to sew and make a unique pattern in the glove material, as a proof of concept for advanced, multimodal cloths'/materials' protection against counterfeiting. The presence and uniform distribution of the modifier NPs in the polymer matrix were confirmed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis (EDX). The concentration of the modifier NPs in the fibers was determined by inductively coupled plasma mass spectrometry, EDX, and magnetic measurements. The luminescence characteristics of the materials were examined by photoluminescence spectroscopy, and their magnetic field-responsive behavior was investigated by a superconducting quantum interference device.

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.

Highly Efficient Flame Retardant Hybrid Composites Based on Calcium Alginate/Nano-Calcium Borate

Hybrid composites with low flammability based on renewable calcium alginate and nano-calcium borate were fabricated using an in situ method through a simple, eco-friendly vacuum drying process. The composites were characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrum (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The combustion behavior and flammability of the composites were assessed by using the limiting oxygen index (LOI) and cone calorimetry (CONE) tests. The composites showed excellent thermal stability and achieved nonflammability with an LOI higher than 60. Pyrolysis was investigated using pyrolysis⁻gas chromatography⁻mass spectrometry (Py-GC-MS) and the results showed that fewer sorts of cracking products were produced from the hybrid composites compared with the calcium alginate. A possible thermal degradation mechanism of composites was proposed based on the experimental data. The combined results indicate that the calcium borate had a nano-effect, accumulating more freely in the hybrid composites and contributing significantly to both the solid phase and gas phase, resulting in an efficient improvement in the flame retardancy of the composites. Our study provides a novel material with promising potentiality for flame retardant applications.

Water Resistant Cellulose - Titanium Dioxide Composites for Photocatalysis

Novel water resistant photocatalytic composites of microfibrillated cellulose (MFC)-polyamide-amine-epichlorohydrin (PAE)-TiO2 nanoparticles (NPs) were prepared by a simple two-step mixing process. The composites produced are flexible, uniform, reproducible and reusable; they can readily be removed from the pollutant once used. Small amount of TiO2 NPs are required for the loaded composites to exhibit a remarkable photocatalytic activity which is quantified here as achieving at least 95% of methyl orange degradation under 150 min of UV light irradiation for the composite with best combination. The cellulose network combined with PAE strongly retains NPs and hinders their release in the environment. PAE dosage (10 and 50 mg/g MFC) controls the NP retention in the cellulose fibrous matrix. As TiO2 content increases, the photocatalytic activity of the composites levels off to a constant; this is reached at 2wt% TiO2 NPs for 10 mg/g PAE and 20wt% for 50 mg/g PAE. SEM and SAXS analysis confirms the uniform distribution of NPs and their formation of aggregates in the cellulose fibre network. These economical and water resistant photocatalytic paper composites made by a simple, robust and easily scalable process are ideal for applications such as waste water treatment where efficiency, reusability and recyclability are important.

Cellulose nanocrystal (CNC)–inorganic hybrid systems: synthesis, properties and applications

Cellulose nanocrystal (CNC), a class of sustainable nanomaterial derived from forest and agro-biomass can serve as nature's storage for carbon dioxide.

Review of recent research on flexible multifunctional nanopapers

Traditional paper and papermaking have struggled with a declining market during the last few decades. However, the incorporation of nanotechnology into papermaking has brought possibilities to develop low-cost, biocompatible and flexible products with sophisticated functionalities. The functionality of nanopapers emerges from the intrinsic properties of the nanofibrous network, the additional loading of specific nanomaterials (NMs), or the additional deposition and patterning of thin films of nanomaterials on the paper surface. A successful development of functional nanopapers requires understanding how the nanopaper matrix, nanofillers, nanocoating pigments, nanoprinting inks, processing additives and manufacturing processes all interact to provide the intended functionality. This review addresses the emerging area of functional nanopapers. This review discusses flexible and multifunctional nanopapers, NMs being used in nanopaper making, manufacturing techniques, and functional applications that provide new important possibilities to utilize papermaking technology. The interface where NM research meets traditional papermaking has important implications for food packaging, energy harvesting and energy storage, flexible electronics, low-cost devices for medical diagnostics, and numerous other areas.

Colorimetric method for the detection of melamine using in-situ formed silver nanoparticles via tannic acid

Melamine toxicity has recently attracted worldwide attention as it causes renal failure and the death of humans and animals. Therefore, developing a simple, fast and sensitive method for the routine detection of melamine is the need of the hour. Herein, we have developed a selective colorimetric method for the detection of melamine in milk samples based upon in-situ formation of silver nanoparticles (AgNPs) via tannic acid. The AgNPs thus formed were characterized by UV-Visible spectrophotometer, transmission electron microscope (TEM), zetasizer and dynamic light scattering (DLS). The AgNPs were used to detect melamine under in vitro condition and in raw milk spiked with melamine. Under optimal conditions, melamine could be selectively detected in vitro within the concentration range of 0.05-1.4μM with a limit of detection (LOD) of 0.01μM, which is lower than the strictest melamine safety requirement of 1ppm. In spiked raw milk, the recovery percentage range was 99.5-106.5% for liquid milk and 98.5-105.5% for powdered milk. The present method shows extreme selectivity with no significant interference with other substances like urea, glucose, glycine, ascorbic acid etc. This assay method does not utilize organic cosolvents, enzymatic reactions, light sensitive dye molecules and sophisticated instrumentation, thereby overcoming some of the limitations of the other conventional methods.

Cellulose-gold nanoparticle hybrid materials

Cellulose and gold nanoparticles have exciting characteristics and new combinations of both materials may lead to promising functional nanocomposites with unique properties. We have reviewed current research on cellulose-gold nanoparticle composite materials, and we present an overview of the preparation methods of cellulose-gold composite materials and discuss their applications. We start with the nanocomposite fabrication methods, covering in situ gold reduction, blending, and dip-coating methods to prepare gold-cellulose nanocomposite hybrids. We then move on to a discussion of the ensuing properties where the combination of gold nanoparticles with cellulose results in functional materials with specific catalytic, antimicrobial, sensing, antioxidant and Surface Enhanced Raman Scattering (SERS) performance. Studies have also been carried out on orientationally ordered composite materials and on the chiral nematic phase behaviour of these nanocomposites. To exert even more control over the structure formation and the resultant properties of these functional materials, fundamental studies on the physico-chemical interactions of cellulose and gold are necessary to understand better the driving forces and limitations towards structuring of gold-cellulose hybrid materials.

Serial number coding and decoding by laser interference direct patterning on the original product surface for anti-counterfeiting

Here, we investigate a method to distinguish the counterfeits by patterning multiple reflective type grating directly on the surface of the original product and analyze the serial number from its rotation angles of diffracted fringes. The micro-sized gratings were fabricated on the surface of the material at high speeds by illuminating the interference fringe generated by passing a high-energy pulse laser through the Fresnel biprism. In addition, analysis of the grating's diffraction fringes was performed using a continuous wave laser.

Turning the Page: Advancing Paper-Based Microfluidics for Broad Diagnostic Application

Infectious diseases are a major global health issue. Diagnosis is a critical first step in effectively managing their spread. Paper-based microfluidic diagnostics first emerged in 2007 as a low-cost alternative to conventional laboratory testing, with the goal of improving accessibility to medical diagnostics in developing countries. In this review, we examine the advances in paper-based microfluidic diagnostics for medical diagnosis in the context of global health from 2007 to 2016. The theory of fluid transport in paper is first presented. The next section examines the strategies that have been employed to control fluid and analyte transport in paper-based assays. Tasks such as mixing, timing, and sequential fluid delivery have been achieved in paper and have enabled analytical capabilities comparable to those of conventional laboratory methods. The following section examines paper-based sample processing and analysis. The most impactful advancement here has been the translation of nucleic acid analysis to a paper-based format. Smartphone-based analysis is another exciting development with potential for wide dissemination. The last core section of the review highlights emerging health applications, such as male fertility testing and wearable diagnostics. We conclude the review with the future outlook, remaining challenges, and emerging opportunities.

A biomolecular recognition approach for the functionalization of cellulose with gold nanoparticles

Materials with new and improved functionalities can be obtained by modifying cellulose with gold nanoparticles (AuNPs) via the in situ reduction of a gold precursor or the deposition or covalent immobilization of pre-synthesized AuNPs. Here, we present an alternative biomolecular recognition approach to functionalize cellulose with biotin-AuNPs that relies on a complex of 2 recognition elements: a ZZ-CBM3 fusion that combines a carbohydrate-binding module (CBM) with the ZZ fragment of the staphylococcal protein A and an anti-biotin antibody. Paper and cellulose microparticles with AuNPs immobilized via the ZZ-CBM3:anti-biotin IgG supramolecular complex displayed an intense red color, whereas essentially no color was detected when AuNPs were deposited over the unmodified materials. Scanning electron microscopy analysis revealed a homogeneous distribution of AuNPs when immobilized via ZZ-CBM3:anti-biotin IgG complexes and aggregation of AuNPs when deposited over paper, suggesting that color differences are due to interparticle plasmon coupling effects. The approach could be used to functionalize paper substrates and cellulose nanocrystals with AuNPs. More important, however, is the fact that the occurrence of a biomolecular recognition event between the CBM-immobilized antibody and its specific, AuNP-conjugated antigen is signaled by red color. This opens up the way for the development of simple and straightforward paper/cellulose-based tests where detection of a target analyte can be made by direct use of color signaling.

Understanding the Dispersive Action of Nanocellulose for Carbon Nanomaterials

This work aims at understanding the excellent ability of nanocelluloses to disperse carbon nanomaterials (CNs) in aqueous media to form long-term stable colloidal dispersions without the need for chemical functionalization of the CNs or the use of surfactant. These dispersions are useful for composites with high CN content when seeking water-based, efficient, and green pathways for their preparation. To establish a comprehensive understanding of such dispersion mechanism, colloidal characterization of the dispersions has been combined with surface adhesion measurements using colloidal probe atomic force microscopy (AFM) in aqueous media. AFM results based on model surfaces of graphene and nanocellulose further suggest that there is an association between the nanocellulose and the CN. This association is caused by fluctuations of the counterions on the surface of the nanocellulose inducing dipoles in the sp² carbon lattice surface of the CNs. Furthermore, the charges on the nanocellulose will induce an electrostatic stabilization of the nanocellulose-CN complexes that prevents aggregation. On the basis of this understanding, nanocelluloses with high surface charge density were used to disperse and stabilize carbon nanotubes (CNTs) and reduced graphene oxide particles in water, so that further increases in the dispersion limit of CNTs could be obtained. The dispersion limit reached the value of 75 wt % CNTs and resulted in high electrical conductivity (515 S/cm) and high modulus (14 GPa) of the CNT composite nanopapers.

Smartphone-based enzymatic biosensor for oral fluid L-lactate detection in one minute using confined multilayer paper reflectometry

The development of smartphone-based biosensors for point-of-care testing (POCT) applications allows realizing "all in one" instruments, with large potential distribution among the general population. With this respect, paper color-based detection performed by reflectance measurement is the most popular, simple, inexpensive and straightforward method. Despite the large number of scientific publications related to these biosensors, they still suffer from a poor detectability and reproducibility related to inhomogeneity of color development, which leads to low assay reproducibility. To overcome these problems, we propose a smartphone paper-based biosensor, in which all the reagents necessary to complete the analysis are co-entrapped on paper in a "wafer"-like bilayer film of polyelectrolytes (Poly (allyl amine hydrochloride/poly(sodium 4-styrene sulfonate)). Using a 3D printing low-cost technology we fabricated the smartphone-based device that consists in a cover accessory attached to the smartphone and incorporating a light diffuser over the flash to improve the image quality, a mini dark box and a disposable analytical cartridge containing all the reagents necessary for the complete analysis. The biosensor was developed exploiting coupled enzyme reactions for quantifying L-lactate in oral fluid, which is considered a biomarker of poor tissue perfusion, a key element in the management of severe sepsis, septic shock and in sports performance evaluation. The developed method is sensitive, rapid, and it allows detecting L-lactate in oral fluid in the relevant physiological range, with a limit of detection of 0.1mmolL^-1. The extreme simplicity of assay execution (no reagents need to be added) and flexibility of fabrication of the device, together with the high assay versatility (any oxidase can be coupled with HRP-based color change reaction) make our approach suitable for the realization of smartphone-based biosensors able to non-invasively detect a large variety of analytes of clinical interest.

Smooth deuterated cellulose films for the visualisation of adsorbed bio-macromolecules

Novel thin and smooth deuterated cellulose films were synthesised to visualize adsorbed bio-macromolecules using contrast variation neutron reflectivity (NR) measurements. Incorporation of varying degrees of deuteration into cellulose was achieved by growing Gluconacetobacter xylinus in deuterated glycerol as carbon source dissolved in growth media containing D2O. The derivative of deuterated cellulose was prepared by trimethylsilylation(TMS) in ionic liquid(1-butyl-3-methylimidazolium chloride). The TMS derivative was dissolved in toluene for thin film preparation by spin-coating. The resulting film was regenerated into deuterated cellulose by exposure to acidic vapour. A common enzyme, horseradish peroxidase (HRP), was adsorbed from solution onto the deuterated cellulose films and visualized by NR. The scattering length density contrast of the deuterated cellulose enabled accurate visualization and quantification of the adsorbed HRP, which would have been impossible to achieve with non-deuterated cellulose. The procedure described enables preparing deuterated cellulose films that allows differentiation of cellulose and non-deuterated bio-macromolecules using NR.

Controlled growth of Cu2O nanoparticles bound to cotton fibres

A green, safe and fast procedure is presented for in situ generation of nanoparticles (NPs) of cuprous oxide (Cu2O) onto cotton fibres at room temperature using water as a solvent. The method is based on a mild surface oxidation of cellulose fibres to generate in a controlled way carboxylic groups acting as a binding site for the adsorption of Cu(2+) via electrostatic coordination. Then, the adsorbed Cu(2+) ions were readly converted into Cu2O by dipping the treated cotton fibres into a aqueous solution of a reducing agent. Field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), as well as UV-vis absorption and emission spectroscopic methods were used to analyse the size, morphology, chemical composition and the crystalline structure of the generated nanoparticles on the fabrics. The morphology of the ensuing Cu2O nanoparticles was shown to be dependent on the reduycing agent used. Antibacterial properties of the modified fibres were also investigated.

Preparation of photochromic paper, using fibre-attached spiropyran polymer networks

Spiropyran-based photochromic paper was prepared by covalent immobilisation of functional polymer networks. The sensitivity of the UV-induced colour change was dynamically adjusted by a damping method. Thereby, a colourimetric UV sensor was designed.

Facile Fabrication of a Silver Nanoparticle Immersed, Surface-Enhanced Raman Scattering Imposed Paper Platform through Successive Ionic Layer Absorption and Reaction for On-Site Bioassays

We introduce a novel, facile, rapid, low-cost, highly reproducible, and power-free synthesizable fabrication method of paper-based silver nanoparticle (AgNP) immersed surface-enhanced Raman scattering (SERS) platform, known as the successive ionic layer absorption and reaction (SILAR) method. The rough and porous properties of the paper led to direct synthesis of AgNPs on the surface as well as in the paper due to capillary effects, resulting in improved plasmon coupling with interparticles and interlayers. The proposed SERS platform showed an enhancement factor of 1.1 × 10(9), high reproducibility (relative standard deviation of 4.2%), and 10(-12) M rhodamine B highly sensitive detection limit by optimizing the SILAR conditions including the concentration of the reactive solution (20/20 mM/mM AgNO3/NaBH4) and the number of SILAR cycles (six). The applicability of the SERS platform was evaluated using two samples including human cervical fluid for clinical diagnosis of human papillomavirus (HPV) infection, associated with cervical cancer, and a malachite green (MG) solution for fungicide and parasiticide in aquaculture, associated with human carcinogenesis. The AgNP-immersed SERS-functionalized platform using the SILAR technique allowed for high chemical structure sensitivity without additional tagging or chemical modification, making it a good alternative for early clinical diagnosis of HPV infection and detection of MG-activated human carcinogenesis.

Tailor-made functional surfaces based on cellulose-derived materials

As one of the most abundant natural materials in nature, cellulose has revealed enormous potential for the construction of functional materials thanks to its sustainability, non-toxicity, biocompatibility, and biodegradability. Among many fascinating applications, functional surfaces based on cellulose-derived materials have attracted increasing interest recently, as platforms for diagnostics, sensoring, robust catalysis, water treatment, ultrafiltration, and anti-microbial surfaces. This mini-review attempts to cover the general methodology for the fabrication of functional cellulose surface and a few popular applications including bioactive and non-adhesive (i.e., anti-fouling and anti-microbial) surfaces.

Raman Characterization of Nanoparticle Transport in Microfluidic Paper-Based Analytical Devices (μPADs)

There is great interest in the use of microfluidic paper-based analytical devices (μPADs) for low-cost diagnostics. In this contribution, we illustrate the utility of Raman spectral imaging for both μPAD characterization and for quantification of the transport of applied reagents and analytes within these devices. We evaluated the transport of nanoscale particles within μPADs using a suite of differentially functionalized gold (AuNP) and silver (AgNP) nanoparticles with diameters of 8-64 nm. Nanoparticle transport within the cellulose matrix was characterized by collection of both Raman and surface-enhanced Raman spectroscopy (SERS) spectral maps that enabled differentiation of cellulose fibers and characterization of analyte deposition patterns. The transport of citrate (cit), BSA, PEG, PVP, and DNA functionalized AuNP and AgNP in wax-printed μPADs was primarily affected by nanoparticle surface chemistry rather than particle size or core composition. Sample pH (3-10) influenced the transport of 15 nm BSA-cit-AuNP, but not 15 nm cit-AuNP, because of the effects of solution pH on the charge and conformation of BSA. Derjaguin, Landau, Verwey, and Overbeek theory (DLVO) and extended DLVO (xDLVO) theory are used to explain the collected experimental results.