Spark plasma welding joining of copper- AISI4140 steel: Microstructures and mechanical properties.

The main aim of this research study was to characterize the microstructures and mechanical properties of Cu-AISI4140 steel solid-state joining created via the spark plasma welding (SPW) method with and without using molds. To explore the effect of mold on the joining of copper/steel, the SPW process was done at 650 °C for 30 min under the pressure of 20 MPa, with and without mold. Microstructural evaluations indicated the diffusion-affected zone (DAZ) in the SPW process increased with mold, as compared to the sample considered in the absence of the mold process. Also, the SPW process with the mold, in response to the lack of the formation of the oxide layer and dead zone, was affected by the process pressure, in comparison to that without the mold process, leading to the reduction of unjointed areas and the formation of micropores constrained at the joining interface; as such, the joining strength was increased from 42 MPa to 90 MPa. The elevation of the applied pressure from 20 MPa to 40 MPa at 650 °C resulted in enhancement of the joining strength up to 106 MPa, but it had no perceptible effect on raising the strength and diffusion affected zone (DAZ) of the joint.

Graphene oxide decorated with gold enables efficient biophotovolatic cells incorporating photosystem I.

This paper describes the use of reduced graphene oxide decorated with gold nanoparticles as an efficient electron transfer layer for solid-state biophotovoltic cells containing photosystem I as the sole photo-active component. Together with polytyrosine-polyaniline as a hole transfer layer, this device architecture results in an open-circuit voltage of 0.3 V, a fill factor of 38% and a short-circuit current density of 5.6 mA cm-2 demonstrating good coupling between photosystem I and the electrodes. The best-performing device reached an external power conversion efficiency of 0.64%, the highest for any solid-state photosystem I-based photovoltaic device that has been reported to date. Our results demonstrate that the functionality of photosystem I in the non-natural environment of solid-state biophotovoltaic cells can be improved through the modification of electrodes with efficient charge-transfer layers. The combination of reduced graphene oxide with gold nanoparticles caused tailoring of the electronic structure and alignment of the energy levels while also increasing electrical conductivity. The decoration of graphene electrodes with gold nanoparticles is a generalizable approach for enhancing charge-transfer across interfaces, particularly when adjusting the levels of the active layer is not feasible, as is the case for photosystem I and other biological molecules.

Fullerenes Enhance Self-Assembly and Electron Injection of Photosystem I in Biophotovoltaic Devices.

This paper describes the fabrication of microfluidic devices with a focus on controlling the orientation of photosystem I (PSI) complexes, which directly affects the performance of biophotovoltaic devices by maximizing the efficiency of the extraction of electron/hole pairs from the complexes. The surface chemistry of the electrode on which the complexes assemble plays a critical role in their orientation. We compared the degree of orientation on self-assembled monolayers of phenyl-C61-butyric acid and a custom peptide on nanostructured gold electrodes. Biophotovoltaic devices fabricated with the C61 fulleroid exhibit significantly improved performance and reproducibility compared to those utilizing the peptide, yielding a 1.6-fold increase in efficiency. In addition, the C61-based devices were more stable under continuous illumination. Our findings show that fulleroids, which are well-known acceptor materials in organic photovoltaic devices, facilitate the extraction of electrons from PSI complexes without sacrificing control over the orientation of the complexes, highlighting this combination of traditional organic semiconductors with biomolecules as a viable approach to coopting natural photosynthetic systems for use in solar cells.

Structural and Electrical Investigation of Cobalt-Doped NiOx/Perovskite Interface for Efficient Inverted Solar Cells.

Inorganic hole-transporting materials (HTMs) for stable and cheap inverted perovskite-based solar cells are highly desired. In this context, NiOx, with low synthesis temperature, has been employed. However, the low conductivity and the large number of defects limit the boost of the efficiency. An approach to improve the conductivity is metal doping. In this work, we have synthesized cobalt-doped NiOx nanoparticles containing 0.75, 1, 1.25, 2.5, and 5 mol% cobalt (Co) ions to be used for the inverted planar perovskite solar cells. The best efficiency of the devices utilizing the low temperature-deposited Co-doped NiOx HTM obtained a champion photoconversion efficiency of 16.42%, with 0.75 mol% of doping. Interestingly, we demonstrated that the improvement is not from an increase of the conductivity of the NiOx film, but due to the improvement of the perovskite layer morphology. We observe that the Co-doping raises the interfacial recombination of the device but more importantly improves the perovskite morphology, enlarging grain size and reducing the density of bulk defects and the bulk recombination. In the case of 0.75 mol% of doping, the beneficial effects do not just compensate for the deleterious one but increase performance further. Therefore, 0.75 mol% Co doping results in a significant improvement in the performance of NiOx-based inverted planar perovskite solar cells, and represents a good compromise to synthesize, and deposit, the inorganic material at low temperature, without losing the performance, due to the strong impact on the structural properties of the perovskite. This work highlights the importance of the interface from two different points of view, electrical and structural, recognizing the role of a low doping Co concentration, as a key to improve the inverted perovskite-based solar cells' performance.

A multifunctional nanocomposite spray dressing of Kappa-carrageenan-polydopamine modified ZnO/L-glutamic acid for diabetic wounds.

Sprayable bioadhesives with exceptional properties were developed for application in wound healing. In this study, a visible light-crosslinkable nanocomposite bioadhesive hydrogel with multifunctional properties was proposed. While methacrylated Kappa-carrageenan (KaMA), mimicking the natural glycosaminoglycan was applied as the hydrogel matrix, various concentrations of polydopamine modified ZnO (ZnO/PD) nanoparticles (0, 0.5, 1 and 2 wt%) was loaded in it to improve its mechanical, antibacterial and cellular properties. Moreover, L-glutamic acid was incorporated in the nanocomposite hydrogel network to accelerate wound healing. The nanocomposite hydrogels revealed significant mechanical property and recovery ability, comparable elasticity with human skin and great adhesiveness. For instance, the tensile strength of KaMA hydrogel enhanced from 64.1 ± 10 to 80.3 ± 8 kPa and elongation jumped from 20 ± 4% to 61 ± 5% after incorporation of 1 wt% ZnO/PD nanoparticles. The nanocomposite hydrogels demonstrated effectual blood clotting ability and biocompatibility, >95% cell viability after 3 days of incubation. In vivo experiments also suggested that L-glutamic acid loaded nanocomposite hydrogel considerably accelerated wound healing with superior granulation tissue thickness than control in a full-thickness skin defect model. Taken together, this visible-light crosslinking nanocomposite hydrogel with significant properties could be used to spray on a wound area to eliminate wound infection and accelerate wound healing process.

Electrochemical molecularly bioimprinted siloxane biosensor on the basis of core/shell silver nanoparticles/EGFR exon 21 L858R point mutant gene/siloxane film for ultra-sensing of Gemcitabine as a lung cancer chemotherapy medication.

In search for improvements in bioanalysis electrochemical sensors, for better assessment of anti-cancer drugs, it is necessary for their detection limits to be minimized and the sensitivity and selectivity to be surpassed simultaneously; whereas, resolving any probable interfering with other medical treatments are considered. In this work, a novel approach was adopted for detection and assessment of Gemcitabine (GEM) as an anti-cancer drug based on evaluating its interaction with EGFR exon 21-point mutant gene. An electrochemical nanobiosensor was invented based on a new molecularly bioimprinted siloxane polymer (MBIS) strategy; in which the EGFR exon 21 acts as an identification probe. The roles of multi-walled carbon nanotubes and Ag nanoparticles (NPs) are to perform as a signal amplifier. The MBIS film was prepared by acid-catalysed hydrolysis/condensation of the sample solution, containing Ag NPs, ds-DNA of EGFR exon 21 point mutant gene, GEM as a template molecule, 3-(aminopropyl) trimethoxysilane (APTMS) and tetraethoxysilane. The interaction between the dsDNA and GEM was investigated by employing the modified biosensor and monitoring oxidation signal of guanine and adenine. The produced biosensor was characterized by XRD, FE-SEM, EDS, FT-IR and differential pulse voltammetry. The oxidation signals of adenine and guanine were in linear range when the device was subjected to various concentrations of GEM, from 1.5 to -93 µM, where a low detection limit 12.5 nmol L-1, and 48.8 nmol L-1 were recorded by guanine and adenine respectively. The developed biosensor did perform very well when employed for the actual samples; the stability was also approved which was acceptable for a reasonable time.

Sprayable and injectable visible-light Kappa-carrageenan hydrogel for in-situ soft tissue engineering.

The aim of this study was to develop injectable and sprayable visible-light crosslinked Kappa-carrageenan (κCA) hydrogel and to investigate the role of polymer concentration (2, 4 and 6 wt%) and degree of methacrylation (6 and 12%) on its properties. It was found that, the average pore sizes, water content and swelling ratio of hydrogel were tunable by changing the methacrylate κCA (KaMA) concentration and methacrylation degree. Furthermore, the mechanical properties of KaMA could be noticeably modulated, depending on the formulation of hydrogel. Tensile and comprehensive modules were enhanced from 68 to 357 kPa and from 213 to 357 kPa, respectively, by increasing KaMA concentration from 2 to 6 wt% and methacrylation degree from 6 to 12%. Furthermore, with increasing methacrylation degree and polymer content, the absorbed energy and energy loss were increased. Moreover, recovery significantly enhanced from 27.3% to 74.4% with increasing polymer content from 2 to 6 wt%. Finally, visible-light crosslinked KaMA hydrogels not only was biocompatible, but also could promote HaLa cell and fibloblasts function. The visible-light crosslinked KaMA is thought to be an exclusive biomaterial as a sprayable hydrogel being able to cover skin injuries or to inject as a bio-printing material to in situ heal soft tissue damages.

Peptide modified paper based impedimetric immunoassay with nanocomposite electrodes as a point-of-care testing of Alpha-fetoprotein in human serum.

Treatment for cancer depends on the type of cancer, and the stage or its development, and thus the need for point-of-care technology that can allow rapid and precise detection of biomarkers is increasing. Here, we present a simple on chip electrical detection of Alpha-fetoprotein (AFP). We rely on using a novel peptide modified plastic-paper microfluidic chips to perform efficient and specific impedimetric detection of AFP in human serum. The chips are prepared from a lower sheet of plastic and upper layer of cellulose chromatography paper modified with silver-20 wt% graphene printed electrodes. Diphenylalanine (FF) was proposed to involve in detection zone of the fabricated microchips in order to improve the sensing performance and the stability of immobilized antibodies according to amine-aldehyde reaction. The target protein is captured on the surface of microchips using specific monoclonal antibodies and the electrical response of the chip is monitored in the presence and absence of different concentrations of AFP. The influence of several parameters including the material types for screen printing of electrodes, FF concentrations, solvent and pH of FF solution on electrical response and cellulose fibers morphology was explored. The impedance measurements of AFP on the fabricated microchip in the optimized parameters exhibited a detection limit of 1 and 10 ng ml-1 in PBS and plasma, respectively. This platform developed here can be adopted to develop systems for rapid detection of biomarkers using portable electric devices.

Investigation and regulation of self-assembled well-ordered nano/microstructures via an aromatic α-amino acid.

In order to invent notable biomaterials, in this research d-phenylalanine as an aromatic α-amino acid has been studied for the synthesis of well-ordered self-assembled architectures such as wires, tubes and sheets under different synthesis conditions. Multiple factors are responsible for phenylalanine formation and herein the influence of several parameters including the substrate, concentration of the amino acid, solvent, pH, and heat treatment was explored. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Atomic Force Microscopy (AFM) were used to monitor the self-assembly process. It was observed that the collective action of different non-covalent interactions plays an important role in phenylalanine self-assembly into well-defined morphologies. In fact, when it was deposited onto different substrates or dissolved in the various solvents and exposed to a certain heat treatment, different supramolecular architectures, including 1D structures, branched structures, and nanosheet arrangements were observed.

Diagnosis of EGFR exon21 L858R point mutation as lung cancer biomarker by electrochemical DNA biosensor based on reduced graphene oxide /functionalized ordered mesoporous carbon/Ni-oxytetracycline metallopolymer nanoparticles modified pencil graphite electrode.

In this present work we made a novel, fast, selective and sensitive electrochemical genobiosensor to detection of EGFR exon 21 point mutation based on two step electropolymerization of Ni(II)-oxytetracycline conducting metallopolymer nanoparticles (Ni-OTC NPs) on the surface of pencil graphite electrode (PGE) which was modified by reduced graphene oxide/carboxyl functionalized ordered mesoporous carbon (rGO/f-OMC) nanocomposite. ssDNA capture probe with amine groups at the5' end which applied as recognition element was immobilized on the rGO/f-OMC/PGE surface via the strong amide bond. Ni-OTC metallopolymer NPs were electropolymerized to rGO/ssDNA-OMC/PGE surface and then hybridization fallows through the peak current change in differential pulse voltammetry (DPV) using Ni-OTC NPs as a redox label. The biosensor was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), FT-IR spectroscopy, energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry and Nitrogen adsorption-desorption analysis. The Ni-OTC current response verified only the complementary sequence indicating a significant reduction current signal in comparison to single point mismatched and non-complementary and sequences. Under optimal conditions, the prepared biosensor showed long-term stability (21 days) with a wide linear range from 0.1 µM to 3 µM with high sensitivity (0.0188 mA/µM) and low detection limit (120 nM).