Optimum Fabrication Conditions Research Articles

Molecularly tailored bifunctional nano-overlayers for efficient and stable inverted perovskite solar cells

Triple cation perovskite solar cells (PSCs) have made remarkable progress in power conversion efficiency (PCE), which is also related to the interface regulation layers between the active layer and electron transport layer (ETL). The ionic nature of the perovskite lattice has enabled approaches to passivate molecular defects through the interaction of functional groups. Herein, a passivator OXD-7 is introduced as a modified layer to passivate surface defects and accelerate electron transfer. It has been observed that OXD-7 can alleviate the micro-strain of the perovskite thin films through intermolecular bonding, which suppresses the iodide vacancy on the perovskite surface. Additionally, the OXD-7 reduces the surface energy of the perovskite films and inhibits the formation of δ-FAPbI3 on the surface of perovskite film. Consequently, the resulting devices demonstrate improved fill factor and device stability. Under optimal fabrication conditions, triple cation mixed perovskite solar cells with an inverted structure achieve a PCE of 23.83%.

Crystallinity-Driven Formation of Highly Arrayed ZnO Nanorods Via Low-Temperature Chemical Bath Deposition on Transparent Conductive Oxide Substrates

The wide-band gap semiconductor zinc oxide (ZnO) nanostructures have attracted much interest in extensive applications such as gas sensors, photoelectrodes in dye sensitized solar cells and catalysts, etc. Among the various synthesis methods of ZnO nanostructures, chemical bath deposition (CBD) method is a low cost and simple technique to synthesize nanostructures. However, there are still remaining issues on growth of well- arrayed ZnO nanostructures with high uniformity and high crystallinity. In this research, we conducted a comprehensive investigation into various parameters, including seed layers, seed-layer thickness, precursor concentration, and reaction time during CBD process. Three kinds of transparent conductive oxide (TCO) films, specifically AZO, GZO, and ITO films, each with a thickness of 300nm, were individually deposited on glass substrates using radio frequency magnetron sputtering and DC magnetron sputtering. These obtained TCO films served as seed layers for the fabrication of ZnO nanorods in CBD process. The solution was prepared with Zn(NO3)2•6H2O and hexathylenetetramine (HMTA) diluted into deionized water, which was heated to 95 °C during CBD process. As the results: 1) Effect of different seed layers: ZnO nanorods exhibited vertically aligned hexagonal structures with uniform morphology when grown on AZO and GZO thin films. The alignment was found to depend on the crystal growth direction of the underlying TCO seed layers. Higher crystallinity of the seed layer contributed to superior alignment, with the crystal mismatch ratio between ZnO nanorods and GZO/AZO films being significantly lower than that with ITO film. 2) The thickness effect investigation was using AZO films varied from 100nm to 300nm. It was found that the thickness influenced the morphology of ZnO nanorods, correlating with the grain sizes of the seed layer thin films. Increasing film thickness led to larger average grain sizes, contributing to the diameter increase of ZnO nanorods in the CBD process, resulting in the improvement of crystallinity of ZnO nanorods. 3) The precursor ratio between concentration ratio of Zn(NO3)2•6H2O and HMTA was set as 2:0.25, 2:0.5, 2:1 and 2:2 individually for ZnO nanorods growth on AZO film. Increasing HMTA concentration initially led to an increase in diameter and length of ZnO nanorods, followed by a decrease at higher ratio of 2:2. The highest crystallinity of ZnO nanorods was obtained at the optimized ratio at 2:1. 4) The growth reaction time was investigated on ZnO nanorods grown on AZO film with concentration ratio of Zn(NO3)2•6H2O and HMTA at 2:1 with varied reacting time from 1 to 5 hours in CBD process. It was found that the reaction time significantly influenced on the growth and crystallinity of well-aligned ZnO nanorods on the as-deposited AZO seed layer. The crystallinity of ZnO nanorods in (0001) growth orientation was improved when the reaction time was increased from 1 hour to 5 hours during the CBD growth. The highest crystallinity was obtained from the ZnO nanorods grown with 5 hours reaction time. When the growth reaction time was increased, more Zn2+ ions were generated and strongly bonded with oxygen. The formed ZnO could be stacked along the c-axis (0001) growth direction and resulted in the length increasing during the CBD process. All fabricated ZnO nanorods showed a high transmittance of over 70% in the visible region. The ZnO nanorods synthesized on AZO substrates with optimized fabrication conditions will be in high potential for optoelectronic applications.

Holographic surface relief diffraction gratings made of hydrogels for direct label-free biosensing of IgGs

This work describes the development of a label-free (LF) biosensing platform for the direct detection of targets based on diffractive structures fabricated with acrylamide-based hydrogels biofunctionalized with proteins and antibodies. Hydrogels containing Bovine Serum Albumin protein (BSA) with different crosslinking degrees were synthesized and characterized to find the optimal conditions for the suitable fabrication of surface relief gratings (SRGs). The bioavailability of BSA-functionalized hydrogels for the specific recognition of anti-BSA antibodies was verified by fluorescence detection. After the hydrogel-based SRG fabrication, diffraction efficiency measures at two different laser wavelengths were used for the direct LF detection of anti-BSA antibodies. The limit of detection in the sub mg L−1 range was read. Additionally, SRGs were prepared with hydrogels biofunctionalized with anti-rabbit antibodies for the direct detection of IgGs from rabbit serum, obtaining similar analytical performance without the necessity of labeling or applying amplification strategies.

One-volt oxide based complementary circuit

In low-power electronics, there is a substantial demand for high-performance p-type oxide thin-film transistors (TFTs) that are capable of efficient operation at low voltages. In this study, we employ anodization to form an aluminum oxide gate dielectric layer, enabling the fabrication of p-type tin oxide (SnO) TFTs that effectively operate at a low voltage of 1 V. Under optimal device fabrication conditions, the SnO TFT demonstrates an on/off current ratio exceeding 103 and a saturation mobility of 1.94 cm2 V−1 s−1 at 1 V operation. The optimal SnO TFT fabrication conditions are subsequently used to fabricate a complementary inverter, comprising a SnO TFT and an n-type indium gallium zinc oxide TFT, achieving a gain of up to 38 at a 1 V supply voltage. Notably, the inverter’s switching point voltage is finely tuned to the ideal value, precisely half of the supply voltage. This oxide-based complementary inverter showcases promising potential in low-power electronics.

Hollow fiber thin-film composite membrane regulated by macrocyclic polyamine molecules for high performance organic solvent nanofiltration

Organic solvent nanofiltration (OSN) technology has the potential to separate and purify organic solvents in high efficiency. The self-supporting structure and ease scaling-up merit of hollow fiber (HF) type membrane make it an attractive option for OSN application. Nevertheless, low solvent permeance is one of technical limitation in conventional HF OSN membranes due to their excessively dense separation layer and limited free volume. Herein, we propose a straightforward methodology to fabricate HF thin-film composite (TFC) OSN membranes having exceptional solvent permeance and solute rejection. This methodology is conducted through the incorporation of macrocyclic molecules, 1,4,7,10-tetraazacyclododecane (Cyclen), into the aqueous monomer solution of m-Phenylenediamine (MPD) during the interfacial polymerization to modulate the separation layer. In this way, the average pore size of the separation layer could be precisely enlarged and narrowed on a sub-nanometer scale. Consequently, the Cyclen-modulated HF TFC OSN membrane exhibits excellent separation performance, with a pure methanol permeance of 76.7 L m−2 h−1 MPa−1 and a pure ethanol permeance of 26.5 L m−2 h−1 MPa−1, which is nearly 60 % increase compared with the baseline TFC membrane, while the Rhodamine B (RDB) rejection only shows a neglectable decrease from 99.7 % to 99.6 % at optimal fabrication conditions. Furthermore, the optimal membrane exhibits remarkable solvent resistance, withstanding a 35 d immersion in N, N-dimethylformamide (DMF) at room temperature without a significant decline in RDB rejection. Additionally, the optimal membrane shows higher than 99 % rejection for Rifampicin (823 Da), which is considerable potential for applications in the separation and recovery of pharmaceuticals. In summary, incorporating macrocyclic polyamine Cyclen into the polyamide layer is a viable method for regulating the physical structure and strengthening the performance of HF OSN membrane.

Modelling and optimization of fabrication parameters for multi-walled carbon nanotubes-filled GFRP composites using RSM and Rao-1 algorithm

This study presents an optimized approach for fabricating multi-walled carbon nanotubes (MWCNTs) filled glass fibre reinforced polymers (GFRP) composites using hybrid optimization approach. The experimental runs performed as per Box-Behnken design of response surface methodology (RSM) by considering three fabrication parameters: MWCNT loading, sonication time (ST), and oven curing temperature (OCT), and the output response, ultimate tensile strength (UTS) is noted. Analysis of variance (ANOVA) is employed to ascertain the significance of the effects that each factor has on UTS and found fabrication variables, OCT, and combined effects of ST and OCT are most significant. Other variables, direct effects of MWCNT loading, interaction effects of all three combinations have influence on UTS. Mathematical modeling is postulated using RSM from which contour plots are drawn to illustrate both direct and interactive effects and reveal fabrication parameters have detrimental effects on UTS. The mathematical equation of UTS is then solved by Rao-1 optimization algorithm and obtained condition is: 1.0% of MWCNT loading, 97.5 min of sonication time, and 76 °C of oven curing temperature and corresponding UTS of 624 MPa. SEM analysis has also been performed to verify the distribution of MWCNTs in the GFRP and observed uniform dispersion of MWCNTs in the developed composite. A confirmatory test validates the predicted optimal fabrication condition derived from the RSM combined with Rao-1 algorithm, ensuring that the methodology has ability to enhance the UTS of MWCNTs-embedded GFRP composites.

An Investigation into the Effects of Processing Factors on the Properties and Scaling-Up Potential of Propranolol-Loaded Chitosan Nanogels.

Chitosan-triphosphate (TPP) nanogels are widely studied drug delivery carrier systems, typically prepared via a simple mixing process. However, the effects of the processing factors on nanogel production have not been extensively explored, despite the importance of understanding and standardising such factors to allow upscaling and commercial usage. This study aims to systematically evaluate the effects of various fabrication and processing factors on the properties of nanogels using a Design of Experiment approach. Hydrodynamic size, polydispersity index (PDI), zeta potential, and encapsulation efficiency were determined as the dependent factors. The temperature, stirring rate, chitosan grade, crosslinker choice, and the interaction term between temperature and chitosan grade were found to have a significant effect on the particle size, whereas the effect of temperature and the addition rate of crosslinker on the PDI was also noteworthy. Moreover, the addition rate of the crosslinker and the volume of the reaction vessel were found to impact the encapsulation efficiency. The zeta potential of the nanogels was found to be governed by the chitosan grade. The optimal fabrication conditions for the development of medium molecular weight chitosan and TPP nanogels included the following: the addition rate for TPP solution was set at 2 mL/min, while the solution was then stirred at a temperature of 50 °C and a stirring speed of 600 rpm. The volume of the glass vial used was 28 mL, while the stirrer size was 20 mm. The second aim of the study was to evaluate the potential for scaling up the nanogels. Size and PDI were found to increase from 128 nm to 151 nm and from 0.232 to 0.267, respectively, when the volume of the reaction mixture was increased from 4 to 20 mL and other processing factors were kept unchanged. These results indicate that caution is required when scaling up as the nanogel properties may be significantly altered with an increasing production scale.

Development of one-step roll-to-roll system with incorporated vacuum sputtering for large-scale production of plasmonic sensing chips

The trade-off relationship between cost and performance is a major challenge in the development of surface-enhanced Raman spectroscopy (SERS) sensors for practical applications. We propose a roll-to-roll system with incorporated vacuum sputtering to manufacture Ag-coated nanodimples (Ag/NDs) on A4-scale films in a single step. The Ag/ND SERS platforms were prepared via O2 ion beam sputtering and Ag sputtering deposition. The concave three-dimensional spaces in the Ag/NDs functioned as hotspots, and their optimal fabrication conditions were investigated with two variables: moving speed and Ag thickness. The entire process was automated, which resulted in highly consistent optical responses (i.e., relative standard deviation of ∼10%). The activation of plasmonic hotspots was demonstrated by electric-field profiles calculated via the finite-difference time-domain method. The wavelength dependency of the Ag/ND platforms was also examined by dark-field microscopy. The results indicate that the developed engineering technique for the large-scale production of Ag/ND plasmonic chips would likely be competitive in the commercial market.

Optimization of Deposition Parameters of SnO2 Particles on Tubular Alumina Substrate for H2 Gas Sensing

Resistive gas sensors, which are widely used for the detection of various toxic gases and vapors, can be fabricated in planar and tubular configurations by the deposition of a semiconducting sensing layer over an insulating substrate. However, their deposition parameters are not often optimized to obtain the highest sensing results. Here, we have investigated the effect of deposition variables on the H2 gas sensing performance of commercially available SnO2 particles on tubular alumina substrate. Utilizing a tubular alumina substrate equipped with gold electrodes, we varied the number of deposited layers, rotational speed of the substrate, and number of rotations of the substrate on the output of the deposited sensor in terms of response to H2 gas. Additionally, the effect of annealing temperatures (400, 500, 600, and 700 °C for 1 h) was investigated. According to our findings, the optimal conditions for sensor fabrication to achieve the best performance were the application of one layer of the sensing material on the sensor with ten rotations and a rotation speed of 7 rpm. In addition, annealing at a lower temperature (400 °C) resulted in better sensor performance. The optimized sensor displayed a high response of ~12 to 500 ppm at 300 °C. This study demonstrates the importance of optimization of deposition parameters on tubular substrates to achieve the best gas sensing performance, which should be considered when preparing gas sensors.

Design and optimization of chitosan-alginate nanoparticles for plant growth hormone indole-3-acetic acid

Excessive use of agrochemicals can lead to environmental degradation, and thus, a potential solution is to control their release using biodegradable polymeric nanoparticles. This study aimed to fabricate indole-3-acetic acid chitosan/alginate nanoparticles (IAA-CANPs) through o/w emulsification and ionotropic gelation, employing a Box-Behnken design (BBD) to evaluate the influence of various factors (alginate: chitosan mass ratio (ALG:CS), TweenTM 80, and IAA concentration) on particle size, zeta potential, and encapsulation efficiency (EE). Response surface methodology (RSM) was used to determine the optimum conditions for nanoparticle fabrication, which were ALG:CS mass ratio of 1:0.10, TweenTM 80 of 1.5% w/v, and IAA of 15 mg/mL. The IAA-CANPs produced under these optimal conditions exhibited an average particle size of 275 ± 19 nm, a polydispersity index (PDI) of 0.37 ± 0.9, a zeta potential of -23.8 ± 0.8 mV, and an EE of 68.5 ± 1.4%. The IAA-CANPs also demonstrated superior physico-chemical stability under UV irradiation exposure compared to free IAA. The IAA-CANPs had stability up to 3 months at 4°C. The release pattern in dissolution media at pH 5.5 and 7.5 indicated a sustained-release behavior, which fit well with the Peppas-Sahlin kinetic model, indicating anomalous diffusion, a non-Fickian diffusion mechanism. These findings suggest that CANPs could be a promising approach for encapsulating and controlling the release of IAA, exhibiting excellent physicochemical stability and potential for agricultural applications.

ZIF-8 membranes on ZIF-8-PVDF/PVDF dual-layer polymeric hollow fiber supports for gas separation

ZIF-8 membranes have attracted extensive research attention due to their ease of synthesis, stable properties, and wide applicability. Compared to expensive inorganic supports, organic polymer supports are more flexible and inexpensive. However, addressing the issue of weak adhesion between the surface of the organic support and the ZIF-8 membrane layer poses a significant challenge. In this study, we present a strategy for preparation of ZIF-8 membrane by the fabrication of an asymmetric dual-layer polymeric hollow fiber support using polyvinylidene fluoride (PVDF) as the material. The outer layer of the support is composed of PVDF embedded with ZIF-8 seeds, while the inner layer consists of pure PVDF. This approach addresses the weak adhesion between the support and the ZIF-8 membrane layer formed through a one-step solvothermal crystallization process. The effects of ZIF-8 seed size, content, and crystallization conditions on the membrane structure and performance are investigated. Under the synergistic molecular sieving effects of ZIF-8 continuous membrane layer and ZIF-8 crystals within the outer layer of the support, larger gas molecules are difficult to penetrate the membrane layer, making the resulting membrane highly selective for the gas separation. Under the optimal fabrication conditions, the H2 permeability of the ZIF-8 membrane is determined to be 1.52 ± 0.1 × 10−7 mol·Pa−1·s−1·m−2, with a H2/N2 ideal separation selectivity of 69.5 ± 4. This method demonstrates simplicity and high reproducibility for preparation of ZIF-8 membranes on dual-layer hollow fibers, and it is expected to be extended to the growth and fabrication of other MOF membranes.

Preparation of an imprinted monolith for field simultaneously selective separation and enrichment of nitrophenols and lead (II) ion in water samples

Imprinted materials have gained significant attention due to its highly specific recognition performance. However, there is no study that using molecule and ion as mixed templates to prepare hybrid imprinted material for simultaneously selective separation and enrichment of molecules and ion. Here, a new strategy employing organic molecule and heavy metal ion as mixed templates to prepare imprinted material was proposed. 2,4-Dinitrophenol (2,4-DNP) and Pb2+ were selected as model templates to in-situ synthesize adsorbent based on imprinted monolith (AIM) in pipette tip. The obtained AIMs were used as the extraction medium of home-made multiple channels in-tip microextraction device (MCMD) for field simultaneously selective entrapment of nitrophenols (NPs) and Pb2+. The selection of functional monomers was well verified with Density function theory. Under the optimal fabrication conditions, the AIM displayed high specific recognition capability towards 2,4-DNP and Pb2+ with imprinted factors 7.31 and 5.20, respectively, and corresponding adsorption capacities were as high as 27.8 mg/g and 20.3 mg/g, respectively. The practicality of proposed AIM/MCMD was evaluated by simultaneously on-site selective capture of NPs and Pb2+ in various environmental waters prior to quantification with HPLC (for NPs) and atomic absorption spectrometry (for Pb2+). Results well evidence that the proposed strategy is feasible in the preparation of imprinted polymer for simultaneously specific extraction of molecules and metal ion, and the developed AIM/MCMD is a useful field sample preparation method for reliable quantification of NPs and Pb2+ in aqueous samples.

Optimization of the elastic modulus for polymeric nanocomposite membranes

AbstractThe mechanical properties of polymeric membranes are critical factors for a successful and durable application in water treatment technologies. Fabricating membranes with optimal mechanical properties require delicate balancing between material, additives, processing conditions, porosity, and many other variables. Several variables to be optimized demands detailed experimental and computational investigations. The design of experiments (DOEs) technique using a validated framework with a computational model for the prediction of the elastic behavior can lower the number of conducted experiments for optimal membrane fabrication conditions. In this study, optimization of the elastic modulus of polymeric membranes is performed using DOE with computational modeling and validated with experiments. The optimum storage modulus of polymeric nano‐filled membranes is determined at an operating temperature of 35°C. DOE is employed with a three‐factor–three‐level problem. The Taguchi DOE is utilized to obtain the experiments scheme, followed by the prediction of the storage modulus and fabrication of the polymeric nano‐filled membrane with the optimum modulus. Predicted results demonstrate that the modulus of polyether sulfone (PES) reinforced with 0.3 wt.% halloysite nanotubes (HNTs) is the optimum combination. The fabricated PES/0.3 wt.% HNT membrane is in good agreement with the predicted modulus with a percentage error of 3%.

Toward a Green Chemistry Approach for the Functionalization of Melamine Foams with Silver Nanoparticles

AbstractThe growing popularity of silver nanoparticles in the field of nanotechnology has created the necessity of developing new sustainable synthesis methods. This study presents a new green in situ functionalization method of melamine foams with silver nanoparticles. The synthesis pathway and the influence of the processing parameters are optimized to phase out 100% of polluting and dangerous solvents while maximizing silver transfer. A deep study of the morphological and chemical changes of the synthesized silver nanoparticles successfully demonstrated that water can be used as the only solvent for obtaining active melamine foams with potential application in multiple fields. Results showed that rising reaction temperatures from environmental to mild conditions (40 °C and 60 °C) is crucial for obtaining high functionalization yields with this green method. Following the optimum fabrication conditions using only water, highly functionalized melamine foams showed a great amount of ultrafine silver nanoparticles distributed over the porous structure.

Elucidating the role of synthesis conditions on Zr-MOF properties and yield

Metal-organic frameworks (MOFs) are a new type of ultra-high surface area porous materials with applications in catalysis, energy storage, and gas adsorption. Compared to other MOFs, Zirconium-based MOFs (Zr-MOFs) demonstrate improved stability due to strong bonds between tetravalent zirconium and carboxylate ligands, making them applicable in real world conditions. This study aims to investigate optimal synthesis conditions for the solvothermal fabrication of Zr-MOFs by looking at two promising tetratopic ligand-based MOFs, Zr-TCPP and Zr-TPTC. By systematically investigating the impact of synthesis parameters on yield, crystallinity, and morphological characteristics, both general and specific trends were determined. The present work demonstrated that the ideal reactant ratio was twice the actual Zr:ligand ratio in the final structure. Stronger acid modulators were found to produce more crystalline samples for MOFs with flexible ligands (Zr-TPTC), where formic acid use resulted in more crystalline samples compared to acetic acid; however, this lowered the yield. The effect of temperature on yield was non-linearly dependent on the reactant ratio used for synthesising flexible Zr-TPTC. For MOFs with rigid ligands (Zr-TCPP), increasing synthesis temperature did not affect yield but decreased crystallite size and improved phase selectivity. Stability tests in water and acid were performed on both MOFs to assess the effect on crystallinity and morphology and the results showed expected trends for Zr-MOFs. The optimized synthesis parameters for Zr-TCPP resulted in a superior method of producing PCN-222 with higher yield and crystallinity. On the other hand, a new Zr-TPTC MOF with high yield and crystallinity was synthesised using the optimized parameters. This study thus elucidates the role of synthesis parameters on Zr-MOF properties and yield and furthers the understanding of MOF synthesis mechanisms, expanding the potential for their applicability in industry.

Molecularly Imprinted Polymer (MIP)-Based Electrochemical Sensor for Determination of Amyloid β-42 in Alzheimer’s Disease

Alzheimer’s disease is the most common type of dementia caused by degeneration of the brain that affects a person’s ability to function independently. Amyloid beta 42 (Aβ- 42) is used as a biomarker for Alzheimer’s disease detection. Increasing the sensitivity of early stage detection of Alzheimer’s disease is challenging. This study mainly focused on the development of signal amplification of Aβ-42 detection using Graphene (G) and Carbon Dot (CD) which were modified on Screen-Printed Carbon Electrode (SPCE) to form graphenecarbon dot/ SPCE. The successful of modified SPCE was investigated by Cyclic Voltammetry (CV). The Molecularly Imprinted Polymer (MIP) was used for specific detection of Aβ- 42. The MIP-based Aβ-42 sensor was prepared by polymerization of o-phenylenediamine (oPD) monomer jointly with Aβ-42 template on the modified SPCE using the Differential Pulse Voltammetry (DPV) technique. The results showed the optimum conditions for the MIP fabrication; an electropolymerization cycle of 15 cycles and elution time of 8 minutes. The MIP-based Aβ-42 sensor exhibited the detection range of Aβ-42 from 1 to 30 pg/ml with the linear range from 0.5 to 20 pg/ml, the R2 from the regression curve of 0.9732 and a Limit of Detection (LOD) of 0.104 ng/ml. The developed MIPbased Aβ-42 sensor was suitable for Aβ-42 detection with cost effectiveness, high sensitivity, and easy to use.

Facile morphological tuning of thin film composite membranes for enhanced desalination performance

Polyamide (PA) membranes with a thin selective layer have been widely investigated for desalination and water treatment. Several modifications have been proposed over the years to tailor the morphology of such thin film composite (TFC) membranes by altering the support and/or selective layers to achieve superior performance. In this study, a facile approach towards fabricating a highly wrinkled selective layer has been demonstrated through bio-inspired modification of the support layer with Y-type zeolites. Results showed that incorporating zeolites in a smaller dimension (200 nm) produced by a unique ball milling technique is favorable for a defect-free selective layer in comparison to larger commercial zeolites. PA membranes formed by the interfacial polymerization (IP) of Piperazine (PIP) and 1,3,5-Benzenetricarbonyl trichloride (TMC) revealed highly wrinkled morphology due to the presence of zeolites in the TFC interlayer. At optimum fabrication conditions, the membrane exhibited a fast transport of 22.5 ± 2.2 Lm-2h-1bar-1 with a salt rejection of 48.6, 91.3, 99.1, and 99.5% for NaCl, MgCl2, MgSO4, and Na2SO4, respectively. Besides the unique preparation of zeolites in smaller dimensions, the novelty of this study lies in the facile membrane pretreatment before IP to achieve wrinkled PA membranes for enhanced nanofiltration performance.

Amperometric bienzymatic biosensor in flow injection analysis system for determination of aspartame in foods.

An amperometric bienzymatic biosensor was developed for the determination of aspartame in a flow injection analysis (FIA) system, consisting of two enzyme reactor columns packed with immobilized α-chymotrypsin (CHY) and alcohol oxidase (AOX) beads and a hydrogen peroxide electrode, connected in series. The CHY and AOX were separately immobilized on glutaraldehyde (GA)-activated beads through covalent bonding. The biosensor fabrication and operational conditions were optimized. The optimal fabrication conditions were: 2% GA with 120min activation time; and 250 U/mL CHY and 100 U/mL AOX, with 180min enzyme immobilization time. The optimal operational conditions were a flow rate of 0.5mL/min and pH 8.0 at room temperature. The developed biosensor showed linearity over the aspartame concentration range 0.01-1.2mM, with a detection limit of 0.005mM. The developed biosensor was satisfactorily applied for detecting aspartame in beverage samples without any excessive pretreatments.

Optimization of synthesis conditions of furfural from sugarcane bagasse using magnetic iron oxide nanoparticles/sulfonated graphene oxide as a catalyst

Catalytic conversion of sugarcane bagasse to furfural is important for the utilization of lignocellulosic waste. In this work, a novel magnetic iron oxide-sulfonated graphene oxide (FSGO) material was synthesized by the hydrothermal combined with co-precipitation method and directly used as the acidic catalyst for converting bagasse to furfural. Fourier transform infrared spectra, X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were utilized in the characterization of materials. Results demonstrated that Fe3O4 nanoparticles were uniformly distributed on the surface of the sulfonate graphene oxide (SGO) sheet, with an average diameter of approximately 10–20 nm. In addition, it is also crucial to determine the optimal furfural fabrication conditions in the presence of the FSGO in order to take full advantage of this material. Thus, this study also provided a thorough assessment of the simultaneous effects of different parameters, including the amount of catalyst, reaction temperature, and time via the response surface methodology (RSM) to determine the most appropriate conditions for the preparation process. According to the Box-Behnken model, the highest furfural production of 172.47 mg/g can be reached under optimal catalytic conditions including the amount of catalyst of 6.5 wt%, reaction temperature of 182 °C, and reaction time of 92 min. In addition, the recovery efficiency and reusability of FSGO catalyst were also investigated, the results of which indicate good reusability after 5 cycles of furfural production from biomass.

Multi-signal amplification electrochemiluminescence biosensor based on GO-CDTPA-AuNPs composites and PET-RAFT for ultrasensitive detection of KRAS G12C mutation

The detection of the Kirsten Rat Sarcoma (KRAS) G12C point mutation plays an important role in the early diagnosis and individualized treatment of non-small cell lung cancer (NSCLC). Herein, a novel electrochemiluminescence (ECL) biosensor for the detection of KRAS G12C mutation via GO-CDTPA-AuNPs composites and photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) multi-signal amplification strategy was fabricated for the first time. In this work, gold nanoparticles (AuNPs) were loaded onto the graphene oxide (GO) surface to form a luminol electrochemiluminescence enhanced composite by simple amide reaction and electrostatic adsorption. Specifically, in the presence of KRAS G12C mutation DNA, i.e. target DNA (tDNA), self-assembled hairpin DNA (hDNA) on the biosensor electrode surface was activated after hybridization with the tDNA to expose a 3′-terminal amino group, that could be further linked to GO-CDTPA-AuNPs composites. To increase luminol-based ECL, GO-CDTPA-AuNPs composites contained a lot of photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) agent loaded onto GO surface. PET-RAFT polymerization of N-acryloxysuccinimide (NAS) monomer was initiated to form polymer chains containing multiple binding sites for luminol. Due to the amplification of luminol attachment sites, very high quantities of luminol could be introduced onto the biosensor electrode surface, resulting in significantly amplified ECL signal intensity. Under optimal biosensor fabrication conditions, a good linear relationship between ECL signal intensity and the logarithm of tDNA concentration was observed over the range of 1 fM to 10 nM with a 0.12 fM limit of detection. Moreover, this strategy exhibited high selectivity and excellent applicability for KRAS G12C mutation detection in the clinical human serum samples. Thus, the fabricated biosensor has great potential for application in the clinical diagnosis.