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Snake bites are a neglected tropical disease, causing mortality and severe damage to various vital organs like the nervous system, kidneys and heart. There is increasing interest in designing new antivenom treatments that are more specific to particular groups (either taxonomic or regional) of species, given the increasing evidence that current polyvalent Indian antivenom is ineffective in many situations. Under these circumstances, being able to detect the species, or a group of species, responsible for the envenomation becomes important. Unfortunately, no such diagnostic tool is available in the Indian market. Such a tool will need to be rapid, sensitive and affordable. To address this need, we have combined the power of nanotechnology and paper microfluidics and herein report a device that has the ability to detect and differentiate viper venom from elapid and scorpion venom. In principle, this assay is based on the release of the dye from the stimuli-responsive glutaraldehyde cross-linked methylene blue-loaded gelatin (GMG) nanoparticles in the presence of snake venom metalloproteases and serine proteases. The developed equipment-free assay can detect and discriminate viper venom from that of elapids and scorpions. The low-end detection limit of the sensor is ∼3.0 ng for the saw-scaled viper Echis carinatus, while the same for Russell's viper Daboia russelii is ∼6.0 ng. The performance of the sensor remains unaltered for different batches of GMG nanoparticles. Altogether, this finding establishes the role of nanotechnology and paper microfluidics in the rapid and accurate detection of viper venom. [ABSTRACT FROM AUTHOR]

Paper-based microfluidics was initially developed for use in ultra-low-cost diagnostics powered passively by liquid wicking. However, there is significant untapped potential in using paper to internally guide porous microfluidic flows using externally applied pressure gradients. Here, we present a new technique for fabricating and utilizing low-cost polymer-laminated paper-based microfluidic devices using external pressure. Known as microfluidic pressure in paper (μPiP), devices fabricated by this technique are capable of sustaining a pressure gradient for use in precise liquid handling and manipulation applications similar to conventional microfluidic open-channel designs, but instead where fluid is driven directly through the porous paper structure. μPiP devices can be both rapidly prototyped or scalably manufactured and deployed at commercial scale with minimal time, equipment, and training requirements. We present an analysis of continuous pressure-driven flow in porous paper-based microfluidic channels and demonstrate broad applicability of this method in performing a variety of different liquid handling applications, including measuring red blood cell deformability and performing continuous free-flow DNA electrophoresis. This new platform offers a budget-friendly method for performing microfluidic operations for both academic prototyping and large-scale commercial device production. [ABSTRACT FROM AUTHOR]

Recently, hydrogen peroxide (H2O2) has been used as a disinfectant in sanitizers for cleaning hands, and solid surfaces of hospitals, offices and homes to prevent the spread of the COVID-19 virus. The effluents from domestic, hospital and municipal waste should be monitored for their H2O2 content to avoid the entry of this toxic pollutant into the ecosystem. Therefore, we developed a low-cost graphene (Gr)-printed paper electrode for determination of H2O2 using cyclic voltammetry (CV). An office inkjet-printer and Gr nano-ink stabilized with ethyl cellulose (EC) were used for the fabrication of printed paper electrodes (PPEs) to determine H2O2 quantitatively. A stable Gr–EC nano-ink (2%) with viscosity and surface tension values of 12 mPa S−1 and 35 mN M−1, respectively, was formulated to obtain conductive electrodes. A wide linear range (2 μM–25 mM) with a better limit of detection (0.28 μM) for the determination of H2O2 was obtained when the Gr–EC/PPE was used as a working electrode. Further, the Gr–EC/PPE was successfully employed for analysis of H2O2 in wastewater. The electrochemical determination of H2O2 using the Gr–EC/PPE as an electrode in CV is rapid, economical, flexible and eco-friendly when compared with previously reported methods. [ABSTRACT FROM AUTHOR]

Paper microfluidics is a rapidly growing subfield of microfluidics in which paper-like porous materials are used to create analytical devices that are well-suited for use in field applications. 3D printing technology has the potential to positively affect paper microfluidic device development by enabling tools and methods for the creation of devices with well-defined and tunable fluidic networks of porous matrices for high performance signal generation. This critical review focuses on the progress that has been made in using 3D printing technologies to advance the development of paper microfluidic devices. We describe printing work in three general categories: (i) solid support structures for paper microfluidic device components; (ii) channel barrier definition in existing porous materials; and (iii) porous channels for capillary flow, and discuss their value in advancing paper microfluidic device development. Finally, we discuss major areas of focus for highest impact on the next generation of paper microfluidics devices. [ABSTRACT FROM AUTHOR]

A series of Ti-doped W18O49 samples were prepared using a convenient solvothermal route. Due to the synergistic effect of doped Ti and oxygen vacancies, the samples showed excellent visible-light photochromic properties. Their performances as light-printable rewritable paper and smart windows showed great application value and promotion value. [ABSTRACT FROM AUTHOR]

Identification of specific antibodies in patient plasma is an essential part of many diagnostic procedures and is critical for safe blood transfusion. Current techniques require laboratory infrastructure and long turnaround times which limits access to those nearby tertiary healthcare providers. Addressing this challenge, a novel and rapid paper-based antibody test is reported. We validate antibody detection with reverse blood typing using IgM antibodies and then generalise the validity by adapting to detect SARS CoV-2 (COVID-19) antibodies in patient serum samples. Reagent red blood cells (RBC) are first combined with the patient plasma containing the screened antibody and a droplet of the mixture is then deposited onto paper. The light intensity profile is analyzed to identify test results, which can be detected by eye and/or with image processing to allow full automation. The efficacy of this test to perform reverse blood typing is demonstrated and the performance and sensitivity of this test using different paper types and RBC reagents was investigated using clinical samples. As an example of the flexibility of this approach, we labeled the RBC reagent with an antibody–peptide conjugate to detect SARS CoV-2 (COVID-19) antibodies in patient serum samples. This concept could be generalized to any agglutination-based antibody diagnostics with blood plasma. [ABSTRACT FROM AUTHOR]

The integration of paper-based devices with fluorescent nanomaterials as recognition elements has offered novel opportunities for biosensing with enhanced sensitivity and selectivity, as well as stable signals. This work innovatively designed a fluorescent paper-based device for enantioselective sensing of D -alanine (D -Ala), where carbon dots (CDs) grafted cellulose paper (PCD) was used as the fluorophore and the in situ generated gold nanoparticles (AuNPs) were used as quenchers. D -α-Amino acid oxidase (DAAO) stereo-selectively catalyzed D -Ala to produce hydrogen peroxide (H2O2), which mediated the in situ formation of PCD/AuNPs composites and quenched the fluorescence of PCD based on fluorescence resonance energy transfer (FRET). Under optimal conditions, the designed PCD/AuNPs demonstrated a reliable quenching response to D -Ala in the range of 1–100 μM and the limit of detection was 0.55 μM. Moreover, the platform was applied to detect D -Ala in serum, simulated gastric fluid samples, and was further employed to determine D -Ala in BGC-823 gastric cancer cells with satisfactory results. Ultimately, the PCD/AuNPs platform provided a novel strategy for the development of reliable and sensitive assays based on paper-based devices. It has great potential to be utilized in enantioselective sensing and clinical early diagnosis. [ABSTRACT FROM AUTHOR]

The practicality of portable fluorescent detectors has attracted widespread attention. Herein, a series of luminogens was obtained via integrating pyrrole/fluorinated-pyrrole with triphenylamine in high yield. The emission performance was modified via varying the F and CN substituents on the pyrrole ring. The compounds TPACHO and TPAFCHO, with aldehyde-group-substituted pyrrole, exhibit significant mechanochromic luminescence (MCL) behavior and typical AIEE properties. The compounds TPA2CN and TPA2FCN can efficiently detect liquid and gaseous hydrazine hydrate, and they can achieve paper-based detection through visually clear emission color switching from yellow/orange to blue. The minimum detectable concentration of hydrazine was 10 mM. Moreover, TPA2CN exhibits good inhibitory activity toward human nasopharyngeal tumor cells (CNE1) and it has application prospects in tumor cell detection and biological cell monitoring. Thus, such functionalized paper can be applied as highly selective discriminating test strips for hydrazine hydrate. [ABSTRACT FROM AUTHOR]

Detection and characterization of DNA damage plays a critical role in genotoxicity testing, drug screening, and environmental health. We developed a fully integrated origami paper-based analytical device (oPAD) for measuring DNA damage. This simple device allows on-paper cell lysis, DNA extraction, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) reaction and signal readout with simple operation steps, enabling rapid (within 30 min) and high throughput assessment of multiple DNA damages induced by exogenous chemical agents. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) have been widely explored for point-of-care testing due to their simplicity, low cost, and portability. μPADs with multiple-step reactions usually require precise flow control, especially flow-delay. This paper reports the numerical, mathematical, and experimental studies of flow delay through wax valves surrounded by PDMS walls on paper microfluidics. The predried surfactant in the sample zone diffuses into the liquid sample which can therefore flow through the wax valves. The delay time is automatically regulated by the diffusion of the surfactant after sample loading. The numerical study suggested that both the elevated contact angle and the reduced porosity and pore size in the wax printed region could effectively prevent water but allow liquids with lower contact angles (e.g., surfactant solutions) to flow through. The PDMS walls fabricated using a low-cost liquid dispenser effectively prevented the leakage of surfactant solutions. By controlling the quantity, diffusion distance, and type of the surfactant predried on the chip, the system successfully achieved a delay time ranging from 1.6 to 20 minutes. A mathematical model involving the above parameters was developed based on Fick's second law to predict the delay time. Finally, the flow-delay systems were applied in sequential mixing and distance-based detection of either glucose or alcohol. Linear ranges of 1–100 mg dL−1 and 1–40 mg dL−1 were achieved for glucose and alcohol, respectively. The lower limit detection (LOD) of glucose and alcohol was 1 mg dL−1. The LOD of glucose was only 1/11 of that detected using μPADs without flow control, indicating the advantage of controlling fluid flow. The systematic findings in this study provide critical guidelines for the development and applications of wax valves in automatic flow delay for point-of-care testing. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) are foundational devices for point-of-care testing, yet suffer from limitations in regards to their sensitivity and capability in handling complex assays. Here, we demonstrate an airflow-based, evaporative method that is capable of manipulating fluid flows within paper membranes to offer new functionalities for multistep delivery of reagents and improve the sensitivity of μPADs by 100–1000 times. This method applies an air-jet to a pre-wetted membrane, generating an evaporative gradient such that any solutes become enriched underneath the air-jet spot. By controlling the lateral position of this spot, the solutes in the paper strip are enriched and follow the air jet trajectory, driving the reactions and enhancing visualization for colorimetric readout in multistep assays. The technique has been successfully applied to drive the sequential delivery in multistep immunoassays as well as improve sensitivity for colorimetric detection assays for nucleic acids and proteins via loop-mediated isothermal amplification (LAMP) and ELISA. For colorimetric LAMP detection of the COVID-19 genome, enrichment of the solution on paper could enhance the contrast of the dye in order to more clearly distinguish between the positive and negative results to achieve a sensitivity of 3 copies of SARS-Cov-2 RNAs. For ELISA, enrichment of the oxidized TMB substrate yielded a sensitivity increase of two-to-three orders of magnitude when compared to non-enriched samples – having a limit of detection of around 200 fM for IgG. Therefore, this enrichment method represents a simple process that can be easily integrated into existing detection assays for controlling fluid flows and improving detection of biomarkers on paper. [ABSTRACT FROM AUTHOR]

In this work, zinc-doped carbon dots (Zn-CDs) were anchored on a three-dimensional wheel type paper-based microfluidic chip, and were decorated with 6-mercaptonicotinic acid (MNA) and L -cysteine (L -Cys) for highly sensitive and rapid fluorescence detection of Cu2+. Zn-CDs were first anchored on paper through the amide bonds between the carboxyl groups of the Zn-CDs and the amino groups of the paper. Afterwards, Zn-CDs were decorated with MNA and L -Cys, effectively preventing the Zn-CDs from aggregation. The nitrogen atom on the pyridine ring and the carboxylic acid groups in MNA and L -Cys coordinated with Cu2+ to form a nonfluorescent ground-state complex, causing the fluorescence quenching of the Zn-CDs. The three-dimensional rotary design could simplify the operation process and achieve simultaneous analysis of multiple samples with different concentrations. Under optimal conditions, the fluorescent sensor exhibits linear response for the determination of Cu2+ in the range from 0.1 to 60 μg L−1 with the detection limit (LOD) of 0.018 μg L−1. The proposed strategy provides a novel way for the highly sensitive detection of Cu2+ in a complex water environment. [ABSTRACT FROM AUTHOR]

The evaluation of the leaching of metals is important in the study of metal-catalyzed reactions. However, analytical methods for the determination of trace metals in organic reaction solution require high purity reagents and time-consuming digestion processes. We present a rapid and sensitive method for the determination of platinum group elements (PGEs) in an organic reaction solution using LA-ICP-MS. Novel sample preparation for the dried solution spot and linear scanning ablation method was developed for the total sampling technique. For a 0.1 μl solution sample, the detection limits of PGEs were 0.034 to 1 ng ml−1 and the detection efficiency of sampling of the detector was 1.5 × 10−5 to 3.3 × 10−4. The proposed method does not require pre-treatment such as digestion, dilution and addition of internal standards to the sample and can be completed within about 5 minutes including sample preparation. To demonstrate the adaptability to organic reaction solution, the quantitative analysis of Pt leaching in continuous-flow hydrogenation reactions with Pt/C as a fixed bed catalyst was performed by the proposed method and compared with the conventional microwave-assisted acid digestion/ICP-MS and isopropanol dilution/ICP-MS methods. The determined concentration showed good agreement with the concentration determined by the conventional methods. The relative deviations of the measured value by LA-ICP-MS were −4.1% from the value obtained by MW/ICP-MS and −3.6% from the value obtained by IPA-dilution/ICP-MS, confirming the accuracy of the proposed method. This method will be a powerful tool for the evaluation of metal leaching and for the analysis of trace metals in organic reaction solutions. [ABSTRACT FROM AUTHOR]

Microcystin has been causing serious environmental pollution; however, the recognition of such compounds is still challenging because of low abundance and coexisting interfering species. In this contribution, we develop a novel microfluidic paper-based colorimetric sensor by exploiting molecular imprinting technology and Fenton reaction for on-site microcystin-RR determination in complex water samples using a smartphone. [ABSTRACT FROM AUTHOR]

A tri-modal paper device based on flower-like CuSe was developed for monitoring Alzheimer's disease (AD)-related miRNA by integrating colorimetric, photothermal and surface-enhanced Raman scattering approaches. Significantly, false-negative signals at the early stage of AD were completely eliminated by using our presented tri-modal strategy. [ABSTRACT FROM AUTHOR]

Exposure to natural rubber latex (NRL) can result in sensitivity to NRL protein with resulting allergic reactions. Low-cost, portable, simple, sensitive analytical tools for NRL protein measurements are needed for rapid and accurate assessments of allergenic risks at the point-of-care (POC) instead of using traditional methods that require large and expensive instruments, long-time analysis, and complex sample preparation steps. Here, an electrochemical paper-based analytical device (ePAD) is presented by combining sample preparation and electrochemical detection within a single device to offer a one-step NRL analysis. The lack of antibodies and/or enzymes against NRL makes POC analysis difficult. In this work, detection is based on electrochemical measurement of the remaining Cu after in situ protein complexation instead of more complex biological assays for the first time. Graphene screen-printed electrodes modified with 1,10-phenanthroline and Nafion were used in the ePAD to improve Cu signal 18-fold relative to unmodified carbon screen-printed electrodes. The optimum parameters including 1,10-phenanthroline concentration, reaction time between Cu and protein, and the starting Cu concentration were 5% w/v, 1 min, and 600 μg mL−1, respectively. In addition to short analysis time (4 min), the system selectivity indicated no other interfering species affecting protein detection. The proposed ePAD achieved an LOD of 3.0 mg dL−1 and a linear range of 10.0–200.0 mg dL−1. Finally, the proposed sensors were applied for NRL protein detection and the results were not significantly different from the traditional Lowry method at 95% confidence. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) have attracted great attention as potential candidates for point-of-care testing (POCT). Nevertheless, only a limited number of μPADs expected to satisfy the standard of Clinical Laboratory Improvement Amendments (CLIA) waived tests as issued by the US Food and Drug Administration (FDA) have been reported. This work introduces a "traffic light type μPAD", enabling highly intuitive semi-quantitative equipment-free naked-eye readout with no need for calibration, subjective interpretation or calculation. Assay results are displayed as traffic light colours reporting 5 analyte concentration levels (green/green & yellow/yellow/yellow & red/red). The device has been designed to never display all three colours simultaneously, eliminating any risk for misinterpretation. The mechanism relies on the modulation of sample flow through a network of paperfluidic channels modified with a hydrophobic to hydrophilic phase-switching substance responsive to H2O2. User operation is limited to sample application, followed by observing a clear and time-independent traffic light signal after approximately 10–30 min. Multiple factors influencing the H2O2 concentration-dependent appearance of a specific traffic light signal were studied. Making use of the possibilities for customising the concentration threshold levels for traffic light colour appearance, quantification of glucose at 5 levels in a clinically relevant concentration range was demonstrated in artificial urine as a model proof-of-concept. This platform is expected to offer the possibility for the future detection of other important metabolites. [ABSTRACT FROM AUTHOR]

The water-soluble bromophenoxy-substituted naphthalimide derivative 1 and its copolymer P1 with acrylamide were synthesized and the photophysical properties of their host–guest complexes with cucurbit[8]uril (CB[8]) were studied. Notably, the host–guest complex CB[8]·1 showed long-lived RTP on filter paper and demonstrated a humidity response, making it suitable for use as an encryption ink. Furthermore, the solid powder of the host–guest complex between P1 and CB[8] exhibited a 4 s afterglow emission. [ABSTRACT FROM AUTHOR]

tert-Butylhydroquinone (TBHQ) residues in foods pose a threat to human health. Therefore, it is necessary to develop a rapid method for TBHQ detection. In this study, a sensitive monoclonal antibody 5C3 (IgG2a subclass) against TBHQ was produced. It possessed a half maximal inhibitory concentration of 7.43 ng mL−1. A gold nanoparticle-based immunochromatographic assay (ICA) was established for the rapid and sensitive screening of TBHQ in soybean oil. Qualitative analysis results were obtained within 10 min and observed with the naked eye. The visual limit of detection (LOD) was 50 ng g−1 and the cut-off value was 1000 ng g−1. A hand-held strip reader was used for quantitative analysis, in which the calculated LOD was defined as 18.68 ng g−1. The average recoveries of TBHQ ranged from 89.55% ± 2.70% to 100.66% ± 3.02% for soybean oil, with a coefficient of variation of 2.89%–7.05%. Therefore, our developed ICA is a useful tool for the rapid and on-site detection of TBHQ in real food samples. [ABSTRACT FROM AUTHOR]

Tacrolimus is one of the most effective and prevalent drugs used to combat vascularized composite allotransplantation rejection. We have fabricated a rapid and easy-to-use six-layer paper based microfluidic device using the principles of competitive immunoassays and vertical flow microfluidics for colorimetric detection of tacrolimus in a small volume of blood. [ABSTRACT FROM AUTHOR]

As the use of non-steroidal anti-inflammatory drugs (NSAIDS) increases, their side effects have also attracted attention. Ibuprofen is one of the most widely-used NSAIDs. In this study, we screened the highly-sensitive and specific antibody 6E10, with an IC50 of 1.92 ng mL−1, and a linear range of 0.53–6.97 ng mL−1. In this study, we developed a rapid lateral flow immunochromatographic assay (ICA) strip method to detect ibuprofen in water or herbal tea. The cut-off limit of the strip is 10 ng mL−1 in water, and concentrations as low as 1 ng mL−1 can be detected in herbal tea samples, with the results obtained by the naked eye within 6 min. All the data were confirmed by high performance liquid chromatography-quadrupole time of flight-mass spectrometry (HPLC-QTOF-MS). This lateral-flow ICA strip is thus a rapid tool for on-site detection and screening of ibuprofen in water and herbal tea. [ABSTRACT FROM AUTHOR]

The combination of electron-deficient viologen ligands with electron-rich POMs is a typical acceptor–donor system that has recently received much attention. Under solvothermal and hydrothermal conditions, by introducing three symmetric viologen ligands into POM-based hybrid materials, we successfully constructed four POMs–viologen inorganic–organic hybrid compounds, namely (1,3-bcbpy)2·(δ-Mo8O26) (1) (1,3-bcbpy·2Cl = 1,1′-bis(3-carboxybenzyl)-4,4′-bipyridine dichloride), {CoII(1,4-bcbpy)2(H2O)2[H2(β-Mo8O26)]}·2H2O·2CH2O (2), (1,4-bcbpy)2·(δ-Mo8O26)·2H2O (3) (1,4-bcbpy·2Cl = 1,1′-bis(4-carboxybenzyl)-4,4′-bipyridine dichloride, CH2O = formaldehyde), and {CuII(1,1-pmbby)2(H2O)[H2(β-Mo8O26)2]}·5H2O·C2H7N (4) (1,1-pmbby·2Cl = 1,1′-[1,4-phenylbis(methylene)]bis-(4,4′-bipyridine)dichloride, C2H7N = dimethylamine). These four compounds exhibit different fascinating structures, especially compound 4 is a typical metal–organic framework. Compounds 1–4 exhibit good discoloration behaviors under various external stimuli. For example, compounds 1–4 showed a positive response to the irradiation from a 300 W Xe lamp. When a positive voltage was applied to the ECD based on compounds 1–4, 1/2/3/4-ECD underwent a significant color conversion. What's more, compound 4 also showed obvious discoloration results after heating. In a word, 1–4 are multifunctional discoloration materials under different external stimuli. In addition, the coated filter paper prepared based on compound 3 can be used as a new printing material medium and can be successfully applied in erasable inkless printing and dual anti-counterfeiting. [ABSTRACT FROM AUTHOR]

It is significant to develop low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) via electrochemical water splitting. Herein, we constructed P-doped NiCo2S4 nanowire arrays on carbon fiber paper (NiCo2S4−xPx/CFP) as a HER electrocatalyst in both acidic and alkaline media. Benefitting from P doping into NiCo2S4, the as-prepared NiCo2S4−xPx/CFP exhibits low HER overpotentials of 80 and 132 mV in acidic and alkaline media at a cathodic current density of 10 mA cm−2, respectively, which are far superior to counterparts of NiCo2S4 nanowire arrays on the carbon fiber paper (NiCo2S4/CFP). Meanwhile, the NiCo2S4−xPx/CFP presents excellent HER stability of 20 hours in acidic and alkaline media. From the results of density functional theory calculations, P doping can not only optimize the hydrogen adsorption energetics on each kind of atomic site of catalysts, but also strengthen the H2O molecule binding ability on the catalyst surface for the alkaline HER and favor kinetics of hydrogen adsorption and H2 formation on the catalyst surface for the acidic HER, eventually improving overall HER performances. The investigation of the HER mechanism modulated by P doping in our work offers novel inspiration to develop highly efficient ternary metal sulfides for the HER. [ABSTRACT FROM AUTHOR]

This work presents the development of a green paper-based analytical device (Green-PAD) array for pH detection. The array was obtained with natural dyes extracted from red cabbage (Brassica oleracea) and butterfly pea flower (Clitoria ternatea); a filter paper was used as a substrate. The RGB indexes of the PADs' colors were extracted from the pictures taken using a smartphone or using a specifically developed RGB detector (Arduino-based) to obtain RGB indexes not affected by the light and the photocamera sensitivity. Multi-technique chemometric models were developed for calculating the pH value, starting from the RGB triplet of each sensing PAD. A preliminary and explorative chemometric analysis with PCA (partial component analysis) and TWPCA (3-way PCA) was carried out. Partial least square regression, PLS, was then applied to correlate the color of the PAD's picture with the solutions' pH. Different solutions at various pHs, ranging from 1 to 13, were obtained by titrating orthophosphoric acid with standardized NaOH, and they were used to create PLS models. Some real samples were examined as a test set, and the results were validated with pH-meter measurements. The ability of the PLS to model the experimental data was satisfactory since a good agreement between the experimental and fitted pH values was obtained. The proposed PADs were prepared with natural dyes and filter papers, so they are completely biodegradable and eco-friendly. Their fabrication does not require toxic or expensive reagents and sophisticated equipment. Also, the developed RGB detector, built-up with low-cost components and recycled batteries, adds value making the measurement cheap, easy and feasible also by non-expert people. [ABSTRACT FROM AUTHOR]

"Waste" is "wealth": the transformation of biomass waste into high value-added substances holds significant environmental and economic importance. In our work, orange peel was effectively transformed into valuable fluorescent carbon quantum dots (CQDs) by solvothermal treatment. The resultant CQDs displayed favorable dispersion and a mean particle size of 3.14 ± 0.71 nm. Moreover, these CQDs exhibited a characteristic excitation-dependent fluorescence behavior, which can produce the maximum emission wavelength at 506 nm with excitation at 400 nm. Upon the introduction of permanganate (MnO4−), the fluorescence intensity of CQDs diminished gradually caused by the inner filter effect (IFE) as well as the static quenching effect (SQE). The results revealed that the CQDs can serve as a fluorescent probe, which possessed high performance in terms of sensitivity for quantitative analysis of MnO4−, boasting a low detection limit of 3.31 μM. Subsequently, the application of this fluorescent probe in actual water samples was further explored, resulting in a recovery rate between 98.18% and 101.69%, with relative standard deviations (RSDs) ranging from 1.85% to 2.68%, which was highly satisfactory. The portable paper-based sensor, fabricated by depositing CQDs onto filter paper, is capable of quantitatively and visually detecting MnO4− in combination with a smartphone, thus providing a rapid on-site detection tool for MnO4−. As far as we know, this study provides the inaugural account of a smartphone-based portable sensor for visual determination of MnO4− by using biomass waste based CQDs, suggesting its immense potential for real-time monitoring applications. [ABSTRACT FROM AUTHOR]

We report a cyclic organosulfide synthesized via a condensation reaction. It can be cycled for 1000 times in half cells. Impressively, it can work with lithiated carbon paper as the anode in ether electrolyte in a full cell. This work shows the promising property of the organosulfide cathode in lithium batteries. [ABSTRACT FROM AUTHOR]

Correction for 'Paper spray mass spectrometry utilizing Teslin® substrate for rapid detection of lipid metabolite changes during COVID-19 infection' by Imesha W. De Silva et al., Analyst, 2020, 145, 5725–5732, DOI: 10.1039/D0AN01074J. [ABSTRACT FROM AUTHOR]

Searching and developing earth-abundant electrocatalysts with predominant activity and favorable stability are significant to resolve increasing environmental pollution and serious energy crisis. In this paper, Mo-based nanowire arrays (NWAs) were synthesized on carbon fiber paper (CFP), and then Ru–MoP NWAs/CFP was successfully assembled through impregnation of Ru and phosphorization. The as-obtained Ru–MoP NWAs/CFP exhibited excellent performance over a broad pH range. As a result, overpotentials of 39.0, 49.9, and 67.1 mV were required to reach the current density of 10 mA cm−2 in 0.5 M H2SO4, 1 M KOH, and 1 M PBS, respectively. The outstanding performance of Ru–MoP NWAs/CFP is mainly related to the introduction of Ru and P atoms, which may enhance the conductivity of the catalyst and develop additional HER active sites. Our work may afford a novel designing approach to develop high performance HER electrocatalysts. [ABSTRACT FROM AUTHOR]

This paper introduces a digital microfluidic (DMF) platform for portable, automated, and integrated Zika viral RNA extraction and amplification. The platform features reconfigurable DMF cartridges offering a closed, humidified environment for sample processing at elevated temperatures, as well as programmable control instrumentation with a novel thermal cycling unit regulated using a proportional integral derivative (PID) feedback loop. The system operates on 12 V DC power, which can be supplied by rechargeable battery packs for remote testing. The DMF system was optimized for an RNA processing pipeline consisting of the following steps: 1) magnetic-bead based RNA extraction from lysed plasma samples, 2) RNA clean-up, and 3) integrated, isothermal amplification of Zika RNA. The DMF pipeline was coupled to a paper-based, colorimetric cell-free protein expression assay for amplified Zika RNA mediated by toehold switch-based sensors. Blinded laboratory evaluation of Zika RNA spiked in human plasma yielded a sensitivity and specificity of 100% and 75% respectively. The platform was then transported to Recife, Brazil for evaluation with infectious Zika viruses, which were detected at the 100 PFU mL−1 level from a 5 μL sample (equivalent to an RT-qPCR cycle threshold value of 32.0), demonstrating its potential as a sample processing platform for miniaturized diagnostic testing. [ABSTRACT FROM AUTHOR]

Polymers and surfactants are used in many technological and industrial applications such as the manufacture of functional materials and coatings, personal care and pharmaceutical products, food science, paints, anti-icing fluids, tertiary oil recovery and the paper industry. Polymer–surfactant mixtures are particularly important in shampoos and conditioners. However, as in almost every other industry over the past five or more decades, the performance of hair care formulations has been significantly improved by the use of petrochemical-derived ingredients. As a result, cosmetic formulations, and hair care formulations in particular, have been based primarily on polymers and surfactants that are neither renewable, nor derived from environmentally friendly processes, nor have a positive environmental impact. This contrasts with the extensive use of natural and renewable products, mainly plant extracts, in cosmetics in ancient times. Therefore, the substitution of currently used ingredients with others of natural origin has been a top priority for the cosmetic industry over the last two decades, and in order to achieve greater consumer acceptance, it is crucial to maintain and, where possible, improve the technical performance of such products. This paper describes the complexities and challenges of developing greener shampoo and conditioner ingredients and formulations to meet current and future needs, and outlines a methodological approach based on model hair surfaces and a selection of appropriate experimental and numerical techniques to achieve our goals. Some encouraging technical routes using biosurfactants, biopolymers and bio-based polymers are presented, along with the significant opportunity to obtain a wide range of green ingredients through molecular design and well-controlled biotechnological processes. Similar concerns apply to other cosmetic products such as waxes, fragrances, bleaching agents, etc. [ABSTRACT FROM AUTHOR]

A well-designed support material between catalyst and substrate can always significantly enhance the performance of an electrode on water oxidation. In this work, a functional Ni and N-doped carbon layer (NNC) was designed on carbon paper (CP) via pyrolysis by using a controlled electrodeposited polyporphyrin as a precursor. Consequently, the fabricated NiFe-LDH/NNC/CP achieved a catalytic current density of 100 mA cm−2 at a small overpotential of 231 mV with a low Tafel slope of 26.0 mV dec−1, as well as high durability for more than 360 h. The insights are that N-doping reinforces the hydrophilicity and the catalyst binding capacity, while Ni-doping intensifies the conductivity. [ABSTRACT FROM AUTHOR]

Physical properties of blood plasma, such as viscosity, serve as crucial indicators of disease. The inherent capillary effect of paper microchannels, coupled with minimal sample requirement, stimulated the advancement of paper-based viscometers. This study presents a precise, non-contact optoelectronic system using a microfluidic platform for the measurement of blood plasma viscosity. Microchannels were defined onto the filter paper using an available and inexpensive wax crayon, without the need for conventional wax printing equipment. The time required for the 5 μL sample to pass a specific distance was measured using two pairs of infrared sensors. Subsequently, this data was sent to the microcontroller, which automatically calculated the viscosity. Throughout the measurements, sample temperature was maintained at a constant 37 °C through an integrated heater with automated control. The microfluidic platform successfully processed real samples, yielding viscosity measurements in under three minutes. Evaluation with fetal bovine serum, spiked with varying protein concentrations in both native and denatured states, demonstrated a precision exceeding 96% compared to conventional Ostwald viscometer readings. For human subjects exhibiting pathologies affecting serum and plasma viscosity compared to physiological norms, strong correlations were observed between resultant values and clinical diagnoses. The proposed device aims to replace expensive and complex optical equipment, offering a safer alternative for measuring plasma viscosity. Unlike similar devices, it eliminates the risk of component deformation due to chemical contact or unsafe irradiation. [ABSTRACT FROM AUTHOR]

The effective integration of nanomaterials with underlying current collectors is a key factor affecting the performance of nonenzymatic glucose sensors, where an inappropriate integration structure often leads to poor electron transport and instability. In this work, a seamless integrated electrode was constructed by the in situ immobilizing of a nickel-based metal-organic framework (Ni-MOF) on a three-dimensional (3D) conductive nickel foam (NF) for highly sensitive and durable glucose sensing. Facilitated by a rapid microwave-assisted reaction, a robust interfacial interaction between the Ni-MOF and the substrate was established through in situ conversion from nickel oxide (NiO). The fabricated Ni-MOF/NF electrode exhibits an excellent limit of detection (LOD) of 2.65 μM and an impressive sensitivity (14.31 mA cm-2 mM-1) within the linear range (4-576 μM), which is significantly boosted compared with that of an electrode prepared by a typical drop-casting method (3.56 mA cm-2 mM-1 in 4-1836 μM). Characterization and electrochemical tests reveal that this integrated structure on the one hand contributes to fast electron transport and thus has enhanced sensitivity and on the other hand leads to exceptional durability with its structural integrity maintained under bending, shaking, and ultrasonication. Moreover, this seamless integration method was also employed to immobilize the Ni-MOF converted from the pre-chemically deposited NiO layer on another type of substrate, 3D carbon paper (CP), demonstrating the versatility of this facile strategy in creating diverse electrochemical electrodes for applications beyond glucose sensing. [ABSTRACT FROM AUTHOR]

A luminescent trimethylamine (TMA) sensor, PTMA-Ir, has been designed and synthesized through immobilizing a phosphorescent iridium(III) complex on a TMA-imprinted polymer. Detailed study shows that the quenching of phosphorescence of PTMA-Ir can serve as a reporter for the binding of TMA on the imprinting sites, thus providing a sensitive, selective, and rapid detection of TMA in both aqueous solutions and gaseous states. Loading PTMA-Ir on filter paper produced a deposition T-Ir, the phosphorescence of which is quenched within 5 s upon exposure to TMA vapor with detection limits of 9.0 ± 0.1 ppm under argon and 15.0 ± 0.1 ppm in an air atmosphere. This work provided an effective method for establishing an imprinting polymer-immobilized luminescent amine sensor. [ABSTRACT FROM AUTHOR]

A scalable, and cost-effective method was employed to prepare self-supported CuSn bimetallic catalyst on carbon paper. The obtained CuSn catalyst demonstrates high faradaic efficiency of CO around or above 90% at a broad potential range from −0.7 to −1.8 V vs. reversible hydrogen electrode, greatly surpassing Cu or Sn counterparts. [ABSTRACT FROM AUTHOR]

A single-step protocol was developed for the hydrolytic hydrogenation of microcrystalline cellulose into sorbitol over commercial carbon-supported Ru, in the presence of gaseous CO2 as an acid source and molecular hydrogen as a reductant. Under these conditions, cellulose was first hydrolysed to glucose by reversibly formed carbonic acid in water and then instantaneously hydrogenated on Ru/C. By tuning the reaction parameters, such as temperature, time and the relative pressure of CO2 and hydrogen gas, cellulose was fully converted at 220 °C in 18 h under 30 and 40 bar of H2 and CO2, respectively, with a sorbitol yield of 81%. Blank experiments revealed that without a catalyst and hydrogen, the reaction exhibited <5% conversion and glucose was the only detected product when the reaction was performed under CO2 pressure. XRD measurements on CO2-treated cellulose surprisingly revealed no noticeable changes in the crystallinity index (<10% with respect to microcrystalline cellulose), suggesting that hydrolytic hydrogenation took place on crystalline, not amorphous, cellulose. Furthermore, not only several cellulosic feedstocks, including filter paper, cotton wool, and cotton fiber, but also typical cellulose-based wastes such as a cardboard pizza box were also tested and under the optimized conditions sorbitol was obtained with yields ranging from 56% up to 72% in all cases. No less significant was the Ru/C catalyst stability, which could be recycled at least six times without any noticeable activity loss. [ABSTRACT FROM AUTHOR]

The electrocatalytic hydrogenation of aromatic rings in benzoic acid derivatives has arisen as a notionally engaging substitute for thermal catalysis under mild conditions. However, the utilization of organic solvents and low faradaic efficiency are incompatible with the principles of green chemistry and energy conservation. Herein, bimetallic PtRu supported on carbon paper developed by co-electrodeposition with optimized atomic ratios maintains an inspiring high conversion of 92.9%, high selectivity of 100% and a high faradaic efficiency of 62.2% for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid in an acidic aqueous electrolyte without external H2, which is the best result to date. The optimized electrocatalyst also exhibits outstanding stability and universality for the electrocatalytic hydrogenation of benzoic acid derivatives. In situ Raman results and theoretical calculations prove that the synergistic effect generated by Ru modifying the electronic structure of Pt simultaneously enhances the capture of benzoic acid molecules and interfacial active hydrogen species and lowers the reaction energy barrier. After adsorbing benzoic acid, more accumulation of electrons around the Ru atom reduces the electron density of phenyl, thereby activating the reaction. Meanwhile, the uniform alloy nanoclusters anchored to the carbon paper surface ensure highly efficient electronic transmission and high dispersion of active components, reducing excessive agglomeration. A proton-exchange membrane reactor is also used to certify the potential of the electrocatalytic hydrogenation of benzoic acid derivatives for large-scale application. [ABSTRACT FROM AUTHOR]

Wood bark is a structurally complex by-product of the pulp and paper industry, which focuses primarily on the valorization of structurally more regular wood xylem components. The aim of this study was the elucidation of the less valorised willow wood counterparts (whole bark, inner bark, sclerenchyma bundles, and parenchymatous tissues) by NMR spectroscopic techniques. This allowed a better understanding of the structural features of macromolecular components of bark (i.e. pectin, hemicellulose, and lignin), thus providing a base for a more rational design of the customized biochemical processes prior to chemical processing of bark. This crucial knowledge contributed to the creation of a protocol/decision tool to select tailored enzymes (discarding the slightest substrate binding) for the biological pre-treatment of bark to a state suitable for chemical pulping. Such a protocol/decision-making tool would significantly improve the efficiency of enzyme selection by 60–70% due to the specific catalytic activity of the enzymes involved. [ABSTRACT FROM AUTHOR]

The New Journal of Chemistry, published by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique, features a variety of papers on different topics in chemistry. The contents list includes papers on antimicrobial peptides, reduction of nitrophenols, supramolecular assembly, synthesis of heterometallic complexes, and the production of collagen-blended nanofiber matrices. Other topics covered in the journal include high entropy alloys, photophysical properties of helicenes, hydrated halogenides, combating multidrug-resistant bacteria, asymmetric synthesis, glucose oxidase intercalation, nanoplatforms for anti-tumor therapy, catalytic degradation of nerve agent simulants, and biological evaluation of novel compounds. The document also includes a correction for a previous paper on a zinc-porphyrin-peptide conjugate. [Extracted from the article]

This article introduces a collection of research papers on intercalation compounds, which are of interest to researchers in various fields. The collection covers topics such as intercalation mechanisms, synthesis methods, host-guest interactions, and structure/property relationships. It also includes papers on energy storage, catalysis, environmental remediation, and biomedical applications. The collection aims to provide valuable insights and encourage collaboration in the field of materials science. [Extracted from the article]

The New Journal of Chemistry, published by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique, is a scientific journal that aims to connect the world with the chemical sciences. The contents list for the September 21, 2024 issue includes a variety of articles and papers on topics such as the synthesis of nanomaterials, nonlinear optical crystals, and the detection of formaldehyde. The journal provides recognition and professional development opportunities for scientists. Some specific papers in this issue cover the preparation of superhydrophobic/superhydrophilic sodium alginate aerogels for oil absorption, improved efficiency of quantum dot-sensitized solar cells, and the electrocatalytic activity of nickel-doped manganese oxide nanorods. Other topics include the synthesis of nanocomposites for supercapacitor performance, the selective adsorption and photodegradation of residual norfloxacin in water, and the targeted delivery of ifosfamide for cancer treatment. [Extracted from the article]

The paper-based culture platform developed by Whitesides readily incorporates tissue-like structures into laboratories with established workflows that rely on monolayer cultures. Cell-laden hydrogels are deposited in these porous scaffolds with micropipettes; these scaffolds support the thin gel slabs, allowing them to be evaluated individually or stacked into thick constructs. The paper-based culture platform has inspired many basic and translational studies, each exploring how readily accessible materials can generate complex structures that mimic aspects of tissues in vivo. Many of these examples have relied on static culture conditions, which result in diffusion-limited environments and cells experiencing pericellular hypoxia. Perfusion-based systems can alleviate pericellular hypoxia and other cell stresses by continually exposing the cells to fresh medium. These perfusion systems are common in microfluidic and organ-on-chip devices supporting cells as monolayer cultures or as 3D constructs. Here, we introduce a continuous flow delivery system, which uses parts readily produced with 3D printing to provide a self-contained culture platform in which cells in paper or other scaffolds are exposed to fresh (flowing) medium. We demonstrate the utility of this device with examples of cells maintained in single cell-laden scaffolds, stacks of cell-laden scaffolds, and scaffolds that contain monolayers of endothelial cells. These demonstrations highlight some possible experimental questions that can be enabled with readily accessible culture materials and a perfusion-based device that can be readily fabricated. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have emerged as promising materials for ion conduction due to their highly tunable structures and excellent electrochemical stability. This review paper explores the mechanisms of ion conduction in COFs, focusing on how these materials facilitate ion transport across their ordered structures, which is crucial for applications such as solid electrolytes in batteries and fuel cells. We discuss the design strategies employed to enhance ion conductivity, including pore size optimization, functionalization with ionic groups, and the incorporation of solvent molecules and salts. Additionally, we examine the various applications of ion-conductive COFs, particularly in energy storage and conversion technologies, highlighting recent advancements and future directions in this field. This review paper aims to provide a comprehensive overview of the current state of research on ion-conductive COFs, offering insights into their potential to design highly ion-conductive COFs considering not only fundamental studies but also practical perspectives for advanced electrochemical devices. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Lab on a Chip," published by the Royal Society of Chemistry. It includes a range of papers on topics such as microfluidics, nanotechnology, and biomedical research. Some of the specific papers mentioned include a programmable and automated optical electrowetting-on-dielectric (oEWOD) driven platform for single cell assay operations, an on-chip phytofluidic device for studying nutrient flow in plant roots, and optimized microfluidic formulation for improved lipid nanoparticle mediated genome editing. The journal covers a variety of scientific disciplines and offers valuable research for those interested in these fields. [Extracted from the article]

Rapid diagnostics are critical infectious disease tools that are designed to detect a known biomarker using antibodies specific to that biomarker. However, a way to detect unknown disease variants has not yet been achieved in a paper test format. We describe here a route to make an adaptable paper immunoassay that can detect an unknown biomarker, demonstrating it on SARS-CoV-2 variants. The immunoassay repurposes cross reactive antibodies raised against the alpha variant. Gold nanoparticles of two different colors conjugated to two different antibodies create a colorimetric signal, and machine learning of the resulting colorimetric pattern is used to train the assay to discriminate between variants of alpha and Omicron BA.5. By using principal component analysis, the colorimetric test patterns can pick up and discriminate an unknown variant that it has not encountered before, Omicron BA.1. The test has an accuracy of 100% and a potential calculated discriminatory power of 900. We show that it can be used adaptively and that it can be used to pick up emerging variants without the need to raise new antibodies. [ABSTRACT FROM AUTHOR]

This document is a contents list for the New Journal of Chemistry, a publication by The Royal Society of Chemistry. It provides information about the journal's editorial, cover image, and articles featured in the current issue. The articles cover a wide range of topics in chemistry, including electrodeposition, supercapacitors, catalysis, and photocatalysis. Some specific papers discussed include the bactericidal effects of zeolitic imidazolate frameworks, the use of nanoparticle-decorated glyceryl monostearate as a targeted drug carrier, and the construction of S@C composites for Mg-S batteries. Other papers explore topics such as metal-organic framework-derived bimetallic oxides as anode materials for lithium-ion batteries, advancements in protection of steel surfaces using polystyrene supported nanoparticles, and the enhancement of vanadium dioxide for supercapacitor applications. The document also includes papers on coordination chemistry, synthetic approaches for coumestan derivatives, and the design of metal complexes for targeting breast cancer. [Extracted from the article]

This document is a contents list for the New Journal of Chemistry, a publication by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. It includes titles and authors of various articles covering topics such as hydrogenation products of fatty acids, macrocycles obtained from condensation reactions, and the characteristics of copper(II) Schiff base complexes as antimicrobial agents. Other papers mentioned in the document discuss catalytic hydrogenation, drug encapsulation, and the removal of pollutants from water. The document includes three papers and a correction, covering topics such as the synthesis of diaminoacetylene, the Z-scheme of 2D structured BCN and Ti MOF heterojunctions for photocatalytic hydrogen evolution, and the crafting of flexible film photocatalysts for formic acid production from CO2 and cyclization of thioamides. [Extracted from the article]

The document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It includes information about the articles and papers featured in the journal's latest issue. The topics covered range from the synthesis of catalysts to the study of coordination polymers and the design of anticancer therapy. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The given document is a list of papers published in the journal Dalton Transactions. The papers cover a range of topics including the synthesis and properties of various compounds, the development of new materials for applications such as light-emitting diodes and supercapacitors, and investigations into the behavior of different chemical compounds. The document provides a comprehensive overview of the research being conducted in the field of chemistry. [Extracted from the article]