Nanowire-based sensor electronics for chemical and biological applications

Double Core-Shell Semiconducting Molecular Chain Halogen-Bridged Metal Complexes with Ohmic Contact Heterojunctions

The fabrication of heterostructures from low-dimensional materials is very challenging, particularly the creation of low-dimensional heterojunctions that can be characterized at an atomic resolution. In a previous work, a two-dimensional (2D) heterostructure made from halogen-bridged metal complexes (MX-Chains), [Ni(chxn)2Br]Br2 (chxn = 1R,2R-diaminocyclohexane) and [Pd(chxn)2Br]Br2, has been synthesized, and the nature of the electronically 1D heterojunction at an atomic resolution was revealed. In the work reported here, we have successfully fabricated double core-shell crystals (Ni-Pd-Ni) from these MX-Chains, using a stepwise electrochemical epitaxial method. Upon cleavage of the heterostructure along the van der Waals layers, a double heterojunction surface is observed. The MX-Chains are aligned in the heterostructure and exhibit anisotropic optical properties based on their 1D electronic systems, as measured using UV-vis-NIR polarized reflectance microscopy. Current-voltage curves at different temperatures are recorded using three probes attached to different areas of the heterostructure and reveal the presence of ohmic conduction through the double 1D heterojunctions. The ohmic contact between the two types of MX-Chains arises from the atomic-scale connection of the MX-Chains at the heterojunction. This work represents the first example of a molecule-based heterostructure that has electronic conductivity and demonstrates electrical conduction through a 1D heterojunction.

The effect of coherent twin boundary migration on the deformation mechanism of Fe-Ni nanowires: molecular dynamics simulation

Fe-Ni nanowires (NWs) containing coherent twin boundaries (CTBs) have received widespread attention in recent years owing to their unique chemical properties. It is important to understand the influence of CTBs on the deformation mechanism of Fe-Ni alloy NWs to develop functional materials based on Fe-Ni alloy NWs. The deformation process of BCC Fe-Ni NWs containing several CTBs under uniaxial stretching was simulated using the molecular dynamics method. It is shown that the NWs of CTBs exhibit two deformation mechanisms under uniaxial stretching. The first mechanism shows that CTB migrates and then completely merges and disappears after yielding the NWs. In this case, if dislocations occur, only few dislocation lines are generated. During the stretching process, the potential energy of atoms within grains increases slowly, while the potential energy of atoms on the CTB increases rapidly. Thus, the whole CTB has a huge activation energy, which leads to its migration. The second mechanism is that during deformation, CTBs of NWs do not migrate. In this case, the potential energy of almost all atoms in the NWs increases. Thus, the local energy of the NWs jumps to a higher level. The higher local energy changes their structure near the CTB from the BCC phase to amorphous structural phases, and the nucleations of deformation twins and those of dislocation lines occur in these regions. Furthermore, the twins and dislocations grow within the grains. These grown twins and dislocations impede the migration of CTB. These findings are beneficial for the better application of alloy nanowires containing coherent twin boundaries.

Integrated Mini-Pillar Platform for Wireless Real-Time Cell Monitoring

Cell culture as the cornerstone of biotechnology remains a labor-intensive process requiring continuous manual oversight and substantial time investment. In this work, we propose an integrated mini-pillar platform for in situ monitoring of multiple cellular metabolism processes, which achieves media anchoring and cell culture through an arrayed mini-pillar chip. The assembly of polyaniline (PANI)/dendritic gold-modified microelectrode biosensors exhibits high sensitivity (63.55 mV/pH) and excellent interference resistance, enabling real-time acquisition of biosensing signals. We successfully employed such integrated devices to real-time measuring pH variations in multiple cells and real-time monitoring of cell metabolism under drug interventions and to facilitate in situ assisted cultivation of 3-dimensional (3D) cell spheroids. This mini-pillar array-based cell culture platform exhibits excellent biosensing sensitivity and real-time monitoring capability, offering considerable potential for the advancement of biotechnology and medical drug development.

Recent advancements in physical and chemical MEMS sensors

Microelectromechanical systems (MEMSs) are microdevices fabricated using semiconductor-fabrication technology, especially those with moving components. This technology has become more widely used in daily life, e.g., in mobile phones, printers, and cars. In this review, MEMS sensors are largely classified as physical or chemical ones. Physical sensors include pressure, inertial force, acoustic, flow, temperature, optical, and magnetic ones. Chemical sensors include gas, odorant, ion, and biological ones. The fundamental principle of sensing is reading out either the movement or electrical-property change of microstructures caused by external stimuli. Here, sensing mechanisms of the sensors are explained using diagrams with equivalent circuits to show the similarity. Examples of multiple parameter measurement with single sensors (e.g. quantum sensors or resonant pressure and temperature sensors) and parallel sensor integration are also introduced.

Conductive magnetic nanowires accelerated electron transfer between C1020 carbon steel and Desulfovibrio vulgaris biofilm

Microbial biofilms are behind microbiologically influenced corrosion (MIC). Sessile cells in biofilms are many times more concentrated volumetrically than planktonic cells in the bulk fluids, thus providing locally high concentrations of chemicals. More importantly, "electroactive" sessile cells in biofilms are capable of utilizing extracellularly supplied electrons (e.g., from elemental Fe) for intracellular reduction of an oxidant such as sulfate in energy metabolism. MIC directly caused by anaerobic biofilms is classified into two main types based on their mechanisms: extracellular electron transfer MIC (EET-MIC) and metabolite MIC (M-MIC). Sulfate-reducing bacteria (SRB) are notorious for their corrosivity. They can cause EET-MIC in carbon steel, but they can also secrete biogenic H2S to corrode other metals such as Cu directly via M-MIC. This study investigated the use of conductive magnetic nanowires as electron mediators to accelerate and thus identify EET-MIC of C1020 by Desulfovibrio vulgaris. The presence of 40 ppm (w/w) nanowires in ATCC 1249 culture medium at 37 °C resulted in 45 % higher weight loss and 57 % deeper corrosion pits after 7-day incubation. Electrochemical tests using linear polarization resistance and potentiodynamic polarization supported the weight loss data trend. These findings suggest that conductive magnetic nanowires can be employed to identify EET-MIC. The use of insoluble 2 μm long nanowires proved that the extracellular section of the electron transfer process is a bottleneck in SRB MIC of carbon steel.

The importance, benefits, and future of nanobiosensors for infectious diseases

Infectious diseases, caused by pathogenic microorganisms such as bacteria, viruses, parasites, or fungi, are crucial for efficient disease management, reducing morbidity and mortality rates and controlling disease spread. Traditional laboratory-based diagnostic methods face challenges such as high costs, time consumption, and a lack of trained personnel in resource-poor settings. Diagnostic biosensors have gained momentum as a potential solution, offering advantages such as low cost, high sensitivity, ease of use, and portability. Nanobiosensors are a promising tool for detecting and diagnosing infectious diseases such as coronavirus disease, human immunodeficiency virus, and hepatitis. These sensors use nanostructured carbon nanotubes, graphene, and nanoparticles to detect specific biomarkers or pathogens. They operate through mechanisms like the lateral flow test platform, where a sample containing the biomarker or pathogen is applied to a test strip. If present, the sample binds to specific recognition probes on the strip, indicating a positive result. This binding event is visualized through a colored line. This review discusses the importance, benefits, and potential of nanobiosensors in detecting infectious diseases.

Unique three-dimensional ordered macroporous dealloyed gold-silver electrochemical sensing platforms for ultrasensitive mercury(II) monitoring

To address the requirement of ultra-sensitive detection of trace mercury(II) (Hg2+) ions in the environment and food, we developed an electrochemical biosensor with super-sensitivity, extremely high selectivity, and reusability. This biosensor comprised two signal amplification components: a three-dimensional macroporous dealloyed (3DOMD) Au-Ag thin-film electrode and a multifunctional encoded Au@Pt nanocage (APNC). As a platform for immobilized capture DNA (cDNA), a 3DOMD Au-Ag thin film prepared by a dealloying method with an active surface area 4.8 times higher than that of 3D macroporous gold films generated by cyclic voltammetry (CV) with sulfuric acid was capable of increasing the sensing surface area while also strengthening the electron transport capacity of the sensing substrate due to its multilayered multi-porous framework. In the presence of Hg2+, probe DNA (pDNA) could be hybridized with the mismatched capture DNA (cDNA) through stable thymine-Hg2+-thymine (T-Hg2+-T) linkages, connecting thionine-APNC to the electrode surface and utilizing the large specific surface area to accomplish highly sensitive detection of Hg2+. With an extremely low Hg2+ detection limit of 2 pM and a detection range from 0.01 to 1000 nM, this technique opened up a new avenue for the ultrasensitive detection of a wider range of heavy metal ions or biomolecules.

Advances in Novel Nanomaterial-Based Optical Fiber Biosensors-A Review

This article presents a concise summary of current advancements in novel nanomaterial-based optical fiber biosensors. The beneficial optical and biological properties of nanomaterials, such as nanoparticle size-dependent signal amplification, plasmon resonance, and charge-transfer capabilities, are widely used in biosensing applications. Due to the biocompatibility and bioreceptor combination, the nanomaterials enhance the sensitivity, limit of detection, specificity, and response time of sensing probes, as well as the signal-to-noise ratio of fiber optic biosensing platforms. This has established a practical method for improving the performance of fiber optic biosensors. With the aforementioned outstanding nanomaterial properties, the development of fiber optic biosensors has been efficiently promoted. This paper reviews the application of numerous novel nanomaterials in the field of optical fiber biosensing and provides a brief explanation of the fiber sensing mechanism.