Reaction Volume Research Articles

Absolute quantification of nucleic acid on digital microfluidics platform based on superhydrophobic–superhydrophilic micropatterning

Digital microfluidics (DMF) shows great potential in the manipulation of individual droplets. However, the limited number of electrode control wirings for droplet control intrinsically restrains the massive generation of pL/nL individual droplets, fundamentally hindering the realization of high throughput applications on DMF such as digital nucleic acid amplification and analysis. This work demonstrates on-chip high throughput digital loop-mediated isothermal amplification (dLAMP) on a DMF platform based on a functional substrate with super-wettability contrast. Exploiting the passive dispensing technique as empowered by electrowetting on dielectric (EWOD) effect, a total of 1818 individual droplets with high uniformity are generated on the super-hydrophilic microarray within 1 min. Separation within the oil phase without tubes and valves can avoid evaporation, ensuring a precise total reaction volume. Absolute quantification of λDNA with a dynamic range of 1–1000 copies/μL is achieved by counting the amount of positive microdroplets after on-chip incubation, demonstrating the strong potential for rapid, low-cost, reliable, and quantitative nucleic acid analysis with high accuracy.

Generation of Multiple Concentration Gradients Using a Two-Dimensional Pyramid Array.

Concentration heterogeneity of diffusible reactants is a prevalent phenomenon in biochemical processes, requiring the generation of concentration gradients for the relevant experiments. In this study, we present a high-density pyramid array microfluidic network for the effective and precise generation of multiple concentration gradients. The complex gradient distribution in the 2D array can be adaptively adjusted by modulating the reactant velocities and concentrations at the inlets. In addition, the unique design of each reaction chamber and mixing block in the array ensures uniform concentrations within each chamber during dynamic changes, enabling large-scale reactions with low reactant volumes. Through detailed numerical simulation of mass transport within the complex microchannel networks, the proposed method allows researchers to determine the desired number of reaction chambers within a given concentration range based on experimental requirements and to quickly obtain the operating conditions with the help of machine learning-based prediction. The effectiveness in generating a multiple concentration gradient environment was further demonstrated by concentration-dependent calcium carbonate crystallization experiments. This device provides a highly efficient mixing and adaptable concentration platform that is well suited for high-throughput and multiplexed reactions.

A wide ranging experimental and kinetic modeling study of TMEDA pyrolysis and oxidation

Traditional liquid propellants like unsymmetrical dimethylhydrazine include several issues, such as toxicity, short storage time and preservation difficulty at low temperatures. For this reason, exploring green and stable propellant fuels is imperative in the development of propellants. Tetramethyl ethylenediamine (TMEDA) is considered to be a promising green propellant fuel with high specific impulse, non-toxicity, and long-term storage stability. Thus, investigating the combustion characteristics of TMEDA and constructing a detailed chemical kinetic mechanism are of fundamental importance in describing its combustion in computational fluid simulation. For this work, ignition delay times of TMEDA were measured in a shock tube at equivalent ratios of 0.5, 1.0 and 2.0, at pressures of 2, 10, and 20 bar, and in the temperature range of 870–1500 K with fixed fuel concentration at 2 %. After the reflected shock at 990–1500 K, the pyrolysis products of 2000 and 5000 ppm TMEDA in Argon were also measured at 5 and 10 bar conditions in a single pulse shock tube. In addition, laminar flame speeds of TMEDA were measured at initial pressures of 1 bar, initial temperatures of 333 and 353 K, and equivalence ratios ranging from 0.8 to 1.5 in a constant volume reactor. The experimental results were simulated using a detailed TMEDA kinetic mechanism. Reaction path analysis and sensitivity analysis were provided to clarify the chemical kinetics of TMEDA oxidation and pyrolysis. The current work provides new experimental data and fundamental analyses for understanding the oxidation and pyrolysis characteristics of TMEDA, and sheds light on optimal directions for future models.

Numerical modelling and process simulation of a post-combustion CO2 capture pilot plant based on a membrane contactor unit

Hollow fiber membrane contactors (HFMC) have gained prominence in post-combustion CO2 capture applications due to their potential for high mass transfer rates, compactness, modularity and versatility. In this work, two pilot plant design have been proposed, an innovative solution which foresees the membrane contactor as CO2 absorption reactor, and a conventional one based on a packed column absorber. A one-dimensional model based on the resistance-in-series method has been developed for the membrane module and validated against experimental data from literature. The other process units have been simulated in Aspen Plus V11. According to the model results the membrane contactor unit is able to guarantee same levels of CO2 removal rates with improved energy performances compared to the conventional packed column absorber. In particular, if the same reactor volume is considered for the two absorber configurations, a reduction in the specific reboiler duty (SRD) of 8.5% is estimated. On the other hand, if the same liquid-to-gas (L/G) ratio is applied, the HFMC is able to guarantee a required reactor volume almost halved (45% reduction). These substantial improvements of the CO2 capture process could lead to lower investment cost and better economic indicators of the CO2 capture plant.

Evaluation of different microbead volumes in a single antigen bead assay for HLA antibody detection

Abstract OBJECTIVE S: The multiplexed single antigen bead (SAB) assay is now commonly used for detection of antibodies to human leukocyte antigens (HLA) in the management of solid organ transplantation. Serum is incubated with microbeads individually coated with unique HLA antigens and the presence of antibody is detected using a secondary antibody. Due to its cost, laboratories may use a lower-than-recommended volume of reagent microbeads, although the impact of microbead volume on assay performance has not been reported. The present study seeks to determine the concordance of an SAB assay when different microbead volumes were used. Although this is also a required laboratory practice when modifications are made to an FDA-cleared assay, requirements for the validation of a multiplexed assay are currently not well-standardized. Hence, this study may also serve as an example framework for validating a clinical multiplexed assay. METHODS SAB (LabScreen, One Lambda) was performed on 14 patient specimens [Mei San T1] selected to provide a range of class I and II HLA antibody levels. Each specimen was tested using three microbead volumes of 5 μL (manufacturer-recommended), 3 μL and 2.5 μL. All reactions were tested in a single session to minimize sources of variability. A mean fluorescence intensity (MFI) of ≥ 2000 was used to define positive beads, which is also the institutional threshold for defining incompatible antigens in solid organ transplantation. Concordance between different bead volumes was calculated using Cohen’s Kappa. Bland-Altman plots were used to visualize bias. All analyses were performed at individual bead level. RESULTS Kappa values were: 0.91 (class I) and 0.95 (class II) for 3 μL vs. 5 μL; 0.90 (class I) and 0.93 (class II) for 2.5 μL vs. 5 µL; 0.97 (class I) and 0.93 (class II) for 2.5 μL vs. 3 μL. Positive bias in MFI values was observed with lower bead volumes and was most pronounced in the 2.5 μL vs. 5 μL comparison; in contrast, MFI values between 2.5 µL and 3 µL were more similar. CONCLUSION Lower-than-recommended microbead volume may be used in the SAB assay without significant impact on classification of incompatible antigens. Although positive bias in MFI values was observed with lower microbead volumes, the impact on positive vs. negative beads assignment was minimal. Since the tested microbead volumes represented 12.5-20% of the total reaction volume, such a change could have caused a matrix effect and impacted antibody-bead binding, leading to differences in MFI values. Hence, individual laboratories modifying the SAB assay should validate such modifications before implementation to ensure the accuracy of HLA antibody assignment.

Highly Multiplexed, Efficient, and Automated Single-Cell MicroRNA Sequencing with Digital Microfluidics.

Single-cell microRNA (miRNA) sequencing has allowed for comprehensively studying the abundance and complex networks of miRNAs, which provides insights beyond single-cell heterogeneity into the dynamic regulation of cellular events. Current benchtop-based technologies for single-cell miRNA sequencing are low throughput, limited reaction efficiency, tedious manual operations, and high reagent costs. Here, a highly multiplexed, efficient, integrated, and automated sample preparation platform is introduced for single-cell miRNA sequencing based on digital microfluidics (DMF), named Hiper-seq. The platform integrates major steps and automates the iterative operations of miRNA sequencing library construction by digital control of addressable droplets on the DMF chip. Based on the design of hydrophilic micro-structures and the capability of handling droplets of DMF, multiple single cells can be selectively isolated and subject to sample processing in a highly parallel way, thus increasing the throughput and efficiency for single-cell miRNA measurement. The nanoliter reaction volume of this platform enables a much higher miRNA detection ability and lower reagent cost compared to benchtop methods. It is further applied Hiper-seq to explore miRNAs involved in the ossification of mouse skeletal stem cells after bone fracture and discovered unreported miRNAs that regulate bone repairing.

Predicting the size of silver nanoparticles synthesised in flow reactors: Coupling population balance models with fluid dynamic simulations

Achieving size control during nanomaterial synthesis is critical for their deployment in numerous applications due to their strong size-properties relationships. However, it remains a challenge in the field due to multi-step mechanisms in nanoparticle synthesis. In this paper, we present an experimentally-validated model able to predict the particle size and distribution of silver nanoparticles synthesised in flow reactors by coupling time-resolved fluid dynamic simulations with population balance. The model reveals fundamental correlations between reactor design and the corresponding size of the nanoparticles. It shows that increasing mixing rate, increases the overall rate of nanoparticle formation, where nanoparticle synthesis takes place homogeneously in the whole of the reaction volume. In contrast, when there is a distinguishable interface between reactant streams (i.e. low mixing rate), nucleation and growth take place in a small fraction of the reaction volume in the interface between the inlet streams. The combination of fast mixing and high average nucleation rate can lead to a burst of nuclei formation translated in small size and narrow size distribution. This work presents a new approach for the use of computational-guided design of reactors for the synthesis of nanomaterials to move the field away from current trial-and-error strategies.

Compact wirelessly-powered photocatalyst-coated spheres: Concept development and application for oxidative wastewater treatment and membrane fouling control

Wirelessly powered photocatalyst-coated spheres (WPS) were successfully developed and wirelessly powered from outside the reactor using resonant inductive coupling. Diverse applications of WPS were demonstrated for the visible light-assisted photocatalytic degradation of methylene blue (textile dye), diclofenac, and triclosan (pharmaceutical compounds) and fouling control of ceramic membranes. These catalyst-coated WPS successfully generated O2− as the main reactive oxygen species (ROS). As demonstrated, these WPS are low-cost, easy to fabricate, have excellent visible light sources, and can be used as the photocatalyst carrier. The acrylic shell of WPS is transparent to light with wavelengths from 300 to 800 nm. Increasing the number of WPS can increase the light intensity proportionally, and 8 WPS can be powered by one power coil outside the reactor. A higher quantity of WPS per reaction volume can be used to improve the reactivity, bringing the use of WPS reactors closer to industrial applications. This is the first report on the use of WPS in the ceramic membrane reactor for fouling control, a 50 % delay compared to control, and highlights the versatility of this system. This work would open up new exploration avenues for membrane fouling control using WPS-based heterogeneous photocatalysis.

Rheology of hydrated plagioclase at lower crustal conditions: Cataclasis, creep and transformational plasticity

Plagioclase feldspar is one of the main rock-forming minerals of the lower continental crust. Assessing its rheology is therefore of particular importance for understanding the mechanical processes acting in convergence zones, where pressure and strain rate increases are often associated with metamorphic reactions and fluid fluxes. In this prospect, we performed axial shortening experiments on “as-is” (∼0.05 wt% H2O) and water-added (∼0.29 wt% H2O) natural plagioclase samples in a Griggs-type apparatus equipped with an acoustic emission monitoring system. Samples were deformed at ∼ 10−6 and ∼ 10−5 s−1, 700–800 °C, and 1.0 GPa in the plagioclase stability field. Experiments have also been performed at 1.5 GPa in order to study the rheological impact of the breakdown reaction Ca-rich plagioclase + water → zoisite + kyanite + quartz + Na-rich plagioclase. Mechanical data indicate that at the conditions studied, the rheology of plagioclase is strongly affected by water content. Microstructural observations confirm that under dry conditions, plagioclase aggregates deform by cataclastic flow. Under wet conditions, dislocation creep appears to be the dominant deformation mechanism, and plagioclase rheology is best described by the following equation, where strain rate, in s−1, is expressed as:ε·=Aσ3.0exp(−(168kJ/mol)/R/T), where σ is the stress in MPa, R is the gas constant, T is the temperature in K, and the pre-exponential term A=10−3.9MPa−3.0s−1. At 1.5 GPa, the reaction is faster under wet conditions but the rheology observed remains identical to that of wet plagioclase in its stability field. In the low water content experiments, plagioclase breakdown induces transient weakening due to fast zoisite nucleation and significant reaction volume change.

One-step synthesis of Ag-loaded Co3O4 as an efficient catalyst for the reduction of p-nitrophenol

The composite comprised of noble metal and non-precious metal oxide as a catalyst offers both low cost and high performance. To obtain this structure, a two-step approach is usually performed, which is time and energy consuming. In this paper, a one-step hydrothermal method was proposed to prepare the Ag/Co3O4 composites with variable silver loadings, using cobalt acetate, silver nitrate, and l-arginine as the reductant. The catalytic activities of these Ag/Co3O4 composites were investigated taking p-nitrophenol (PNP) reduction using NaBH4 as the reducing agent. The results demonstrated that the Ag/Co3O4 composite exhibited superb catalytic reduction capacity towards PNP benefiting from the even dispersion of elemental Ag particles on the surface of Co3O4 microspheres. A reduction ratio of 89.33 % and a reaction rate of 0.1558 min−1 for PNP were obtained within 15 min under the optimal reaction conditions: Ag0.008/Co3O4 amount of 0.01 g·L−1, NaBH4 dosage of 7 mmol·L−1, PNP concentration of 0.108 mmol·L−1, a total reaction volume of 1000 mL and a temperature of 25 °C. Besides, the composite showed stable catalytic performance after five continuous uses, maintaining a PNP reduction rate above 82 %. This work presents an effective way for the facile preparation of noble metal-loaded composite catalysts.

Boosting the efficiency of supported undecamolybdophosphate catalyst by tailoring acid-redox properties for direct oxidative cross-esterification of aldehydes

Aiming to develop a novel heterogeneous catalyst for single-step oxidative cross-esterification of aldehydes to ester with enhanced activity and selectivity under benign conditions, here we report the synthesis of defect-regulated undecamolybdophosphate supported on ZSM-5. The enhancement in acidity was achieved by exchanging the available Na+ with protons using an ion-exchange protocol. The structural and morphological features of synthesized catalysts (20 % PMo11/ZSM-5-H) were confirmed by in-depth characterization such as acidity measurement, FT-IR, TGA, surface area measurement SEM, TEM, and PXRD. The synthesized catalysts were used for direct oxidative esterification reaction with environmentally benign oxidants (O2 and H2O2). The effect of various reaction parameters such as %loading of PMo11, amount of catalyst, reaction time, and reaction temperature and volume of methanol on activity and selectivity was studied. The comparative studies of supported analogous phosphomolybdates with the present catalyst showed that the enhancement in acidity and modulation in redox properties of 20 % PMo11/ZSM-5-H was found propitious. The novelty lies in obtaining excellent selectivity of the ester (>95 %) with an exceptionally high turnover number (>15323) with an environmentally benign oxidant O2. The scope and limitations of the present catalytic system were also explored by employing different aldehydes and alcohols under optimized conditions. The stability and recycling studies showed that the synthesized catalyst is truly heterogeneous and can be recycled at a minimum of six cycles. From the comparative data of the reported catalysts as well as control experiments, it was concluded that the synergistic effects of enhanced acidities and tailored redox sites played vital roles in the superior performance of the present catalytic system. Based on the results, a plausible reaction mechanism was also proposed.

Production and Purification of Soy Leghemoglobin from Pichia pastoris Cultivated in Different Expression Media

Plant-based meat alternatives, exemplified by Impossible Foods’ Impossible Burger, offer a sustainable, ethical substitute for traditional meat, closely mimicking the taste and appearance of meat by utilizing soy leghemoglobin (LegH), a 16 kDa holoprotein found in soy plants structurally similar to heme in animal meat. Cultivation medium plays an important role in bioprocess development; however, medium development or optimization can be labor intensive, and thus the use of previously reported media can be enticing. In this study, we explored the expression of recombinant LegH in Pichia pastoris in various reported cultivation media (BSM, BMGY, FM22, D’Anjou, BSM/2, and RDM) and using different feeding approaches (µ-stat and mixed feed with sorbitol). Our findings indicate that optimization techniques tailored to the specific process did not increase LegH yields, highlighting the need to investigate strain-specific strategies. We also utilized the collected process data to create and train a novel artificial neural network-based soft sensor for estimating cell biomass, relying solely on standard bioreactor measurements (such as stirrer speed, dissolved oxygen, O2 enrichment, base feed, glycerol feed, methanol feed, and reactor volume). This soft sensor proved to be robust and exhibited a strong correlation (3.72% WCW) with experimental data.

Computational evaluation of light propagation in cylindrical bioreactors for optogenetic mammalian cell cultures.

Light-inducible regulation of cellular pathways and gene circuits in mammalian cells is a new frontier in mammalian genetic engineering. Optogenetic mammalian cell cultures, which are light-sensitive engineered cells, utilize light to regulate gene expression and protein activity. As a low-cost, tunable, and reversible input, light is highly adept at spatiotemporal and orthogonal regulation of cellular behavior. However, light is absorbed and scattered as it travels through media and cells, and the applicability of optogenetics in larger mammalian bioreactors has not been determined. In this work, we computationally explore the size limit to which optogenetics can be applied in cylindrical bioreactors at relevant height-to-diameter ratios. We model the propagation of light using the radiative transfer equation and consider changes in reactor volume, absorption coefficient, scattering coefficient, and scattering anisotropy. We observe sufficient light penetration for activation in simulated bioreactors with sizes of up to 80,000 L at maximal cell densities. We performed supporting experiments and found that significant attenuation occurs at the boundaries of the system, but the relative change in intensity distribution within the reactor was consistent with simulation results. We conclude that optogenetics can be applied to bioreactors at an industrial scale and may be a valuable tool for specific biomanufacturing applications.

Photocatalytic Simulation of Phenol Waste Degradation Using Titanium Dioxide (TiO2) P25-Based Photocatalysts

Phenol waste treatment is vital in industries such as polymer production, coal gasification, refinery, and coke production. Photocatalytic technology using semiconductor materials offers an effective and ecofriendly approach to degrade phenol. TiO2 P25 is a widely used photocatalyst, known for its cost-effectiveness, favorable optical and electronic properties, high photoactivity, and photostability. The PHOTOREAC application, a recently developed MATLAB-based software, simulates the degradation of phenol using visible light. A study that combines existing literature and research revealed that pH significantly influences photocatalytic activity, with an optimum pH of 7 for TiO2 P25-mediated phenol degradation. The recommended photocatalyst concentration ranged from 0 to 10 g/L for reactor volumes between 25 and 60 mL, and from 0 to 5 g/L for 100-mL reactors. Phenol wastewater volume and light intensity also impact degradation efficiency. Adequate oxygen supply, achieved through bubbling and mixing, is essential for the formation of radical compounds. The Ballari kinetic model proved to be the most suitable for phenol degradation with TiO2 P25. Thus, by combining PHOTOREAC simulations with experimental data, the treatment process could be optimized to achieve higher degradation efficiency and estimate the treatment time for specific waste degradation levels. This study contributes to the advancement of phenol waste treatment and the development of improved photocatalytic wastewater treatment technologies.

Double-shelled NiS/SnS@N-doped carbon nanoboxes engineered from NiSn(OH)6 cube templates for advanced sodium-ion battery anodes

Overcoming the sluggish reaction kinetics and volume effects of metal sulfides as anodic materials for sodium-ion batteries remains a challenging task. In this study, a multistep template-engaged strategy is employed for the first time to fabricate hierarchical double-shells NiS/SnS@nitrogen doped carbon (NiS/SnS@NC) nanoboxes, utilizing NiSn(OH)6 cubes as starting templates. The synergistic combination of sophisticated sulfide components and the double-shell structure effectively mitigates volume variation, reduces nanoparticle cohesion, and enhances electrode reaction kinetics. Notably, NiS/SnS@NC exhibits outstanding stability under high current density while maintaining a high capacity. Comprehensive kinetics analysis reveals that the enhanced sodium storage of NiS/SnS@NC can be attributed to its low interface reaction resistance, significant capacitive contribution, and rapid mass-transfer kinetics. The stepwise (de)sodiation processes of the NiS/SnS@NC anode are elucidated through various in/ex-situ characterization techniques, confirming the alternating reaction activity alternations between two components, which acts as a self-buffering and self-conductivity mechanism to enhance sodium storage. Finally, a practical application is demonstrated, where a well-designed NiS/SnS@NC||Na3V2(PO4)2F3/C full cell shows promising performance, achieving a high capacity of 265 mAh/g after 1000 cycles at 2.0 A/g. This work′s synthesis strategy and research findings contribute to advancing the exploration and application of NiSn(OH)6 and its derivatives in the field of energy storage and beyond.

Prolonged hydrogen production by engineered green algae photovoltaic power stations

Interest in securing energy production channels from renewable sources is higher than ever due to the daily observation of the impacts of climate change. A key renewable energy harvesting strategy achieving carbon neutral cycles is artificial photosynthesis. Solar-to-fuel routes thus far relied on elaborately crafted semiconductors, undermining the cost-efficiency of the system. Furthermore, fuels produced required separation prior to utilization. As an artificial photosynthesis design, here we demonstrate the conversion of swimming green algae into photovoltaic power stations. The engineered algae exhibit bioelectrogenesis, en route to energy storage in hydrogen. Notably, fuel formation requires no additives or external bias other than CO2 and sunlight. The cellular power stations autoregulate the oxygen level during artificial photosynthesis, granting immediate utility of the photosynthetic hydrogen without separation. The fuel production scales linearly with the reactor volume, which is a necessary trait for contributing to the large-scale renewable energy portfolio.

Technical and Economic Review of Biogas Utilization from Traditional Market Organic Waste

This research is a continuation of previous research, namely the Study of the Potential of Gorontalo City Central Market Organic Waste as Raw Material for Biogas Reactors which was completed in 2023 and has produced characteristics of organic waste generation at the Central Market of Gorontalo City. As a continuation of previous research, this research will try to design a Biogas Reactor by utilizing organic waste at the Central Market of Gorontalo City as a traditional market which produces waste every day and is a problem for the city government. The materials used in writing this article are based on the results of research carried out by the author in 2023 from other selected articles related to the use of organic waste as an energy source through the fermentation process in a biogas reactor (digester). From the technical aspect, the research has succeeded in designing a fixed dome type biogas reactor, reactor volume 15.3 m3 with reinforced concrete construction complete with a cost budget and detailed drawings for its construction. Meanwhile, from an economic aspect, an economic analysis has been carried out and it can be concluded that investment with initial capital of Rp. 78,793,000, economically feasible as indicated by the parameters NPV > 0, IRR (22.22%) > MARR (10.07%), B/C Ratio 2.0 times, and Payment Period 12 years 0 months.

A two-stage Fe(VI) oxidation process enhances the removal of bisphenol A for potential application

Ferrate (Fe(VI)) has been extensively studied as a green oxidant to treat wastewater. But Fe(VI) oxidation still faces several challenges for application, such as the sensitivity of Fe(VI) to pH and the restrictions on the Fe(VI) utilization efficiency for pollutant elimination at low concentration levels. This study proposed a two-stage Fe(VI) oxidation process to enhance the bisphenol A (BPA) removal for potential applicability, consisting of the adsorption by CNTs of stage I and the degradation by Fe(VI) of stage II. The Fe(VI) utilization efficiency in the two-stage process (0.848) was higher than that in one-stage processes (0.727) and Fe(VI) alone system (0.504) at pH 9. In stage I, the adsorption process had good compliance with the Langmuir isotherm model and pseudo-second-order kinetic model. In stage II, the effective utilization of low-concentration Fe(VI) was 2.45 times more than Fe(VI) alone, and the reduction of reaction volume was beneficial to further enhance utilization. The probe experiments (sulfoxide) and the degradation experiments of other electron-donating/withdrawing pollutants (e.g., atrazine, benzoic acid) demonstrated that Fe(IV) and Fe(V) were major oxidizing species in the two-stage process. The regeneration experiments showed that CNTs still had acceptable adsorption and catalytic capabilities after five cycles. Finally, the intermediate products in the two-stage process were detected and four possible degradation pathways of BPA were proposed. These findings were meaningful for the practical application of Fe(VI) oxidation to overcome the conditional limitation and improve the utilization.

Simultaneous detection of acetamiprid and carbendazim based on Raman-silent spectral window tags-mediated surface-enhanced Raman scattering aptasensor coupled with magnetic separation

Surface-enhanced Raman scattering (SERS) has been widely used for detecting pesticide residues. Nevertheless, the spectral interference of sample matrix still exists, and the simultaneous detection of multiple pesticides is challenging. In this work, specific simultaneous detection of acetamiprid (ACE) and carbendazim (CBZ) in complex sample matrix was achieved by using two Raman tag molecules (prussian blue, PB; 4-(mercaptomethyl) benzonitrile, MBN) whose peaks were in the Raman-silent spectral window. Two Raman nanoprobes were synthesized by adding MBN and PB into the Au and Ag core-shell gap and coupled with two complementary DNA (cDNA), respectively. Meanwhile, two aptamer-incubated Fe3O4/Au nanoparticles were used as capture molecules. Results showed that the Raman intensity at 2077 cm−1 and 2228 cm−1 had an inverse tendency with ACE and CBZ concentrations, respectively. Under the optimal conditions of aptamer, cDNA concentration, and reaction volume ratio, the SERS aptasensor showed a wide linear range of 0.01 ∼ 1 mg/kg with limit of detection of 9.43 μg/kg to ACE and 9.17 μg/kg to CBZ. The result of recovery experiment showed that there was no significant difference between SERS method and HPLC method (p > 0.05). It turned out that the SERS aptasensor had a good resistance to spectral interference of matrix and easy separation, which can specifically detect ACE and CBZ in complex matrix simultaneously. SERS combined with nano-sensor elements will be conducive to the on-site detection of various hazardous substances in food safety.

Flexible fiber optoelectrodes integrating Perovskite-Nafion-ITO layers for efficient photoelectrocatalytic water purification

Photoelectrocatalytic processes (PECs) combine photocatalysis and electrochemical principles to enhance charge carrier generation and stability within nanomaterials (NMs). Nano-enabled PECs can be used for water purification or hydrogen production. While most PEC studies focus on nanomaterial discovery to improve charge carriers generation and separation, PEC reactor design is important to maximize energy efficiency of light delivery to activate photocatalysts. Current designs face challenges due to low energy efficiencies because most reactor designs orientate light sources perpendicular to flat photocatalyst-coated electrode surfaces, and light must pass through glass materials plus water. We developed a low-cost, physically flexible catalytic polymeric optical fiber (POF) architecture, called optoelectrode fibers, embedded with electrically-conductive indium tin oxide (ITO) nanomaterials (NMs) plus TAB3Bi2Br7I2 perovskite (ABI) visible-photocatalysts in Nafion-PVDF polymers surface layer. The PEC-POF architecture achieves > 6000% larger surface area than flat glass electrodes, > 90% organic pollutant removal in water, and > 300% better incident photon-to-current than the same ABI-NM deposited on a conventional ITO-coated flat glass-plate under low energy irradiation. POFs are useful because are agonistic to the type of NM, facilitating deposition of NMs tunable to specific wavelengths using LED or polychromatic light sources. Bundling large numbers of POF optoelectrodes together achieves reactors with orders of magnitude higher packing geometries (m2 of catalyst surface per m3 of reactor volume) than flat-electrode PEC reactors, enabling the optoelectrode fiber to address environmental problems.