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Diabetes mellitus affects a significant percentage of the world's population, and the incidence of this disease is expected to increase exponentially in the coming years. The development of practical and low-cost glucose sensors is of utmost importance to monitor and manage diabetes and diabetes associated complications. In this scope, a nonenzymatic glucose sensor was produced by growing zinc oxide (ZnO) nanorods on a cellulose-based substrate by microwave-assisted hydrothermal synthesis. The developed sensor relies on ZnO nanorods' photocatalytic ability to photo-oxidize glucose, eliminating the need to use an oxidase enzyme. The quantification of glucose is based on the quenching of the ZnO's photoluminescence signal by the hydrogen peroxide produced during the nonenzymatic oxidation of this monosaccharide. The developed sensor possesses a sensitivity of 1.46%/mM, a linear range between 0.5 and 30 mM, and a limit of detection of 0.103 mM. The sensor showed good selectivity for glucose, and it was also demonstrated that there was a high correlation between the glucose concentration values obtained using the sensor's calibration curve and the clinical data of human plasma samples, therefore validating the use of ZnO nanorods to monitor the glucose concentration in human plasma samples. This work reports for the first time a ZnO-based eco-friendly, stable, and highly selective alternative for glucose monitoring, pointing to a promising future for metal oxide nanostructures for biomedical sensors. [ABSTRACT FROM AUTHOR]

Expanding the single molecule detection, enabled by laser-induced graphene (LIG) technology, for portable and on-site analysis, a dual molecule system with a two-working-electrode architecture was developed for ascorbic acid (AA) and amoxicillin (AMOX) detection, which are currently used in aquaculture and persist as water contaminants. The biorecognition element of each target compound was a suitable molecularly imprinted polymer (MIP). The AMOX MIP was developed herein for the first time and assembled by electropolymerization of eriochrome black T (EBT). It showed a wide linear response from 50 nM to 100 μM, with a sensitivity of −13.32 μA/decade. Calibration curves revealed good squared correlation coefficients (R2 > 0.99) with a limit of detection (LOD) of 11.98 nM. AA MIP was assembled according to a previous work reported in the literature, displaying a linear response from 1.5 to 4 mM and a sensitivity of 1.356 μA/decade. The developed dual-LIG device was further tested in real samples and successfully applied to the analysis of binary mixtures prepared in environmental water samples from a well. Overall, the proposed device allows in situ analysis of two different molecules and holds an exceptionally low-cost design when compared to competing architectures in the literature, and the fabrication method here employed offers the possibility of easily adjusting the desired architecture on demand. [ABSTRACT FROM AUTHOR]

The market for flexible, hybrid, and printed electronic systems, which can appear in everything from sensors and wearables to displays and lighting, is still uncertain. What is clear is that these systems are appearing every day, enabling devices and systems that can, in the near future, be crumpled up and tucked in our pockets. Within this context, cellulose-based modified nanopapers were developed to serve both as a physical support and a gate dielectric layer in field-effect transistors (FETs) that are fully recyclable. It was found that the impregnation of those nanopapers with sodium (Na + ) ions allows for low operating voltage FETs (<3 V), with mobility above 10 cm 2 V -1 s -1 , current modulation surpassing 10 5 , and an improved dynamic response. Thus, it was possible to implement those transistors into simple circuits such as inverters, reaching a clear discrimination between logic states. Besides the overall improvement in electrical performance, these devices have shown to be an interesting alternative for reliable, sustainable, and flexible electronics, maintaining proper operation even under stress conditions.

Halide perovskites have been widely explored for numerous optoelectronic applications among which phototransistors have appeared as one of the most promising light signal detectors. However, it is still a great challenge to endow halide perovskites with both mobility and high photosensitivity because of their high sensitivity to moisture in ambient atmosphere. Here, we explore an FAPbBr 3 perovskite quantum dot (QD) phototransistor with bandlike charge transport and measure a dark hole mobility of 14.2 cm 2 V -1 s -1 at ambient atmosphere. Attaining both high mobility and good optical figures of merit, a detectivity of ∼10 16 Jones is achieved, which is a record for halide perovskite nanocrystals. Simple A-site salt (FABr) treatments offer a mechanism for connecting between perovskite QDs for better charge transfer in high-quality devices. All of these important properties are superior to most advanced inorganic semiconductor phototransistors, indicating a promising future in optoelectronic applications.

Alzheimer's disease (AD) is one of the most common forms of dementia affecting millions of people worldwide. Currently, an easy and effective form of diagnosis is missing, which significantly hinders a possible improvement of the patient's quality of life. In this context, biosensors emerge as a future solution, opening the doors for preventive medicine and allowing the premature diagnosis of numerous pathologies. This work presents a pioneering biosensor that combines a bottom-up design approach using paper as a platform for the electrochemical recognition of peptide amyloid β-42 (Aβ-42), a biomarker for AD present in blood, associated with visible differences in the brain tissue and responsible for the formation of senile plaques. The sensor layer relies on a molecularly imprinted polymer as a biorecognition element, created on the carbon ink electrode's surface by electropolymerizing a mixture of the target analyte (Aβ-42) and a monomer ( O -phenylenediamine) at neutral pH 7.2. Next, the template molecule was removed from the polymeric network by enzymatic and acidic treatments. The vacant sites so obtained preserved the shape of the imprinted protein and were able to rebind the target analyte. Morphological and chemical analyses were performed in order to control the surface modification of the materials. The analytical performance of the biosensor was evaluated by an electroanalytical technique, namely, square wave voltammetry. For this purpose, the analytical response of the biosensor was tested with standard solutions ranging from 0.1 ng/mL to 1 μg/mL of Aβ-42. The linear response of the biosensor went down to 0.1 ng/mL. Overall, the developed biosensor offered numerous benefits, such as simplicity, low cost, reproducibility, fast response, and repeatability less than 10%. All together, these features may have a strong impact in the early detection of AD., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

The current trend for smart, self-sustainable, and multifunctional technology demands for the development of energy harvesters based on widely available and environmentally friendly materials. In this context, ZnSnO 3 nanostructures show promising potential because of their high polarization, which can be explored in piezoelectric devices. Nevertheless, a pure phase of ZnSnO 3 is hard to achieve because of its metastability, and obtaining it in the form of nanowires is even more challenging. Although some groups have already reported the mixing of ZnSnO 3 nanostructures with polydimethylsiloxane (PDMS) to produce a nanogenerator, the resultant polymeric film is usually flat and does not take advantage of an enhanced piezoelectric contribution achieved through its microstructuration. Herein, a microstructured composite of nanowires synthesized by a seed-layer free hydrothermal route mixed with PDMS (ZnSnO 3 @PDMS) is proposed to produce nanogenerators. PFM measurements show a clear enhancement of d 33 for single ZnSnO 3 versus ZnO nanowires (23 ± 4 pm/V vs 9 ± 2 pm/V). The microstructuration introduced herein results in an enhancement of the piezoelectric effect of the ZnSnO 3 nanowires, enabling nanogenerators with an output voltage, current, and instantaneous power density of 120 V, 13 μA, and 230 μW·cm -2 , respectively. Even using an active area smaller than 1 cm 2 , the performance of this nanogenerator enables lighting up multiple LEDs and other small electronic devices, thus proving great potential for wearables and portable electronics.

Technical development for thin-film fabrication is essential for emerging metal-oxide (MO) electronics. Although impressive progress has been achieved in fabricating MO thin films, the challenges still remain. Here, we report a versatile and general thermal-induced nanomelting technique for fabricating MO thin films from the fiber networks, briefly called fiber-to-film (FTF) process. The high quality of the FTF-processed MO thin films was confirmed by various investigations. The FTF process is generally applicable to numerous technologically relevant MO thin films, including semiconducting thin films (e.g., In 2 O 3 , InZnO, and InZrZnO), conducting thin films (e.g., InSnO), and insulating thin films (e.g., AlO x ). By optimizing the fabrication process, In 2 O 3 /AlO x thin-film transistors (TFTs) were successfully integrated by fully FTF processes. High-performance TFT was achieved with an average mobility of ∼25 cm 2 /(Vs), an on/off current ratio of ∼10 7 , a threshold voltage of ∼1 V, and a device yield of 100%. As a proof of concept, one-transistor-driven pixel circuit was constructed, which exhibited high controllability over the light-emitting diodes. Logic gates based on fully FTF-processed In 2 O 3 /AlO x TFTs were further realized, which exhibited good dynamic logic responses and voltage amplification by a factor of ∼4. The FTF technique presented here offers great potential in large-area and low-cost manufacturing for flexible oxide electronics.

Solution-based indium-gallium-zinc oxide (IGZO) nanoparticles deposited by spin coating have been investigated as a resistive switching layer in metal-insulator-metal structures for nonvolatile memory applications. Optimized devices show a bipolar resistive switching behavior, low programming voltages of ±1 V, on/off ratios higher than 10, high endurance, and a retention time of up to 10 4 s. The better performing devices were achieved with annealing temperatures of 200 °C and using asymmetric electrode materials of titanium and silver. The physics behind the improved switching properties of the devices is discussed in terms of the oxygen deficiency of IGZO. Temperature analysis of the conductance states revealed a nonmetallic filamentary conduction. The presented devices are potential candidates for the integration of memory functionality into low-cost System-on-Panel technology., Competing Interests: The authors declare no competing financial interest.

In the past decade, solution-based dielectric oxides have been widely studied in electronic applications enabling the use of low-cost processing technologies and device improvement. The most promising are the high-κ dielectrics, like aluminum (AlO x ) and hafnium oxide (HfO x ), that allow an easier trap filling in the semiconductor and the use of low operation voltage. However, in the case of HfO x , a high temperature usually is needed to induce a uniform and condensed film, which limits its applications in flexible electronics. This paper describes how to obtain HfO x dielectric thin films and the effect of their implementation in multilayer dielectrics (MLD) at low temperatures (150 °C) to apply in thin film transistors (TFTs) using the combination of solution combustion synthesis (SCS) and ultraviolet (UV) treatment. The single layers and multilayers did not show any trace of residual organics and exhibited a small surface roughness (<1.2 nm) and a high breakdown voltage (>2.7 MV·cm -1 ). The resulting TFTs presented a high performance at a low operation voltage (<3 V), with high saturation mobility (43.9 ± 1.1 cm 2 ·V -1 ·s -1 ), a small subthreshold slope (0.066 ± 0.010 V·dec -1 ), current ratio of 1 × 10 6 and a good idle shelf life stability after 2 months. To our knowledge, the results achieved surpass the actual state-of-the-art. Finally, we demonstrated a low-voltage diode-connected inverter using MLD/IGZO TFTs working with a maximum gain of 1 at 2 V.

Highly luminescent CsPbBr 3 perovskite quantum dots (QDs) have gained huge attention in research due to their various applications in optoelectronics, including as a light absorber in photovoltaic solar cells. To improve the performances of such devices, it requires a deeper knowledge on the charge transport dynamics inside the solar cell, which are related to its power-conversion efficiency. Here, we report the successful fabrication of an all-inorganic CsPbBr 3 perovskite QD sensitized solar cell and the imaging of anomalous electrical potential distribution across the layers of the cell under different illuminations using Kelvin probe force microscopy. Carrier generation, separation, and transport capacity inside the cells are dependent on the light illumination. Large differences in surface potential between electron and hole transport layers with unbalanced carrier separation at the junction have been observed under white light (full solar spectrum) illumination. However, under monochromatic light (single wavelength of solar spectrum) illumination, poor charge transport occurred across the junction as a consequence of less difference in surface potential between the active layers. The outcome of this study provides a clear idea on the carrier dynamic processes inside the cells and corresponding surface potential across the layers under the illumination of different wavelengths of light to understand the functioning of the solar cells and ultimately for the improvement of their photovoltaic performances.

Solution processing of amorphous metal oxides has lately been used as an option to implement in flexible electronics, allowing a reduction of the associated costs and high performance. However, the research has focused more on the semiconductor layer rather than on the insulator layer, which is related to the stability and performance of the devices. This work aims to evaluate amorphous aluminum oxide thin films produced by combustion synthesis and the influence of far-ultraviolet (FUV) irradiation on the properties of the insulator on thin-film transistors (TFTs) using different semiconductors, in order to have compatibility with flexible substrates. An optimized dielectric layer was obtained for an annealing of 30 min assisted by FUV exposure. These thin films were applied in gallium-indium-zinc oxide TFTs as dielectrics showing the best results for TFTs annealed at 180 °C with FUV irradiation: good reproducibility with a subthreshold slope of 0.11 ± 0.01 V dec -1 and a turn-on voltage of -0.12 ± 0.05 V, low operating voltage, and good stability over time. Finally, the dielectric layer was applied in solution-processed indium oxide (In 2 O 3 ) TFTs at low temperature, 180 °C, with a short processing time being compatible with flexible electronic applications.

The charge transfer dynamics at interfaces are fundamental to know the mechanism of photovoltaic processes. The internal potential in solar cell devices depends on the basic processes of photovoltaic effect such as charge carrier generation, separation, transport, recombination, etc. Here we report the direct observation of the surface potential depth profile over the cross-section of the ZnO nanorods/Cu2O based solar cell for two different layer thicknesses at different wavelengths of light using Kelvin probe force microscopy. The topography and phase images across the cross-section of the solar cell are also observed, where the interfaces are well-defined on the nanoscale. The potential profiling results demonstrate that under white light illumination, the photoinduced electrons in Cu2O inject into ZnO due to the interfacial electric field, which results in the large difference in surface potential between two active layers. However, under a single wavelength illumination, the charge carrier generation, separation, and transport processes between two active layers are limited, which affect the surface potential images and corresponding potential depth profile. Because of changes in the active layer thicknesses, small variations have been observed in the charge carrier transport mechanism inside the device. These results provide the clear idea about the charge carrier distribution inside the solar cell in different conditions and show the perfect illumination condition for large carrier transport in a high performance solar cell.

Solution-processed field-effect transistors are strategic building blocks when considering low-cost sustainable flexible electronics. Nevertheless, some challenges (e.g., processing temperature, reliability, reproducibility in large areas, and cost effectiveness) are requirements that must be surpassed in order to achieve high-performance transistors. The present work reports electrolyte-gated transistors using as channel layer gallium-indium-zinc-oxide nanoparticles produced by solvothermal synthesis combined with a solid-state electrolyte based on aqueous dispersions of vinyl acetate stabilized with cellulose derivatives, acrylic acid ester in styrene and lithium perchlorate. The devices fabricated using this approach display a ION/IOFF up to 1 × 10(6), threshold voltage (VTh) of 0.3-1.9 V, and mobility up to 1 cm(2)/(V s), as a function of gallium-indium-zinc-oxide ink formulation and two different annealing temperatures. These results validates the usage of electrolyte-gated transistors as a viable and promising alternative for nanoparticle based semiconductor devices as the electrolyte improves the interface and promotes a more efficient step coverage of the channel layer, reducing the operating voltage when compared with conventional dielectrics gating. Moreover, it is shown that by controlling the applied gate potential, the operation mechanism of the electrolyte-gated transistors can be modified from electric double layer to electrochemical doping.

Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm2 V(-1) s(-1).

We reported here "aqueous-route" fabrication of In2O3 thin-film transistors (TFTs) using an ultrathin solution-processed ZrOx dielectric thin film. The formation and properties of In2O3 thin films under various annealing temperatures were intensively examined by thermogravimetric analysis, Fourier transform infrared spectroscopy, and atomic force microscopy. The solution-processed ZrOx thin film followed by sequential UV/ozone treatment and low-temperature thermal-annealing processes showed an amorphous structure, a low leakage-current density (∼1 × 10(-9) A/cm(2) at 2 MV/cm), and a high breakdown electric field (∼7.2 MV/cm). On the basis of its implementation as the gate insulator, the In2O3 TFTs based on ZrOx annealed at 250 °C exhibit an on/off current ratio larger than 10(7), a field-effect mobility of 23.6 cm(2)/V·s, a subthreshold swing of 90 mV/decade, a threshold voltage of 0.13 V, and high stability. These promising properties were obtained at a low operating voltage of 1.5 V. These results suggest that "aqueous-route" In2O3 TFTs based on a solution-processed ZrOx dielectric could potentially be used for low-cost, low-temperature-processing, high-performance, and flexible devices.

pH is a vital physiological parameter that can be used for disease diagnosis and treatment as well as in monitoring other biological processes. Metal/metal oxide based pH sensors have several advantages regarding their reliability, miniaturization, and cost-effectiveness, which are critical characteristics for in vivo applications. In this work, WO3 nanoparticles were electrodeposited on flexible substrates over metal electrodes with a sensing area of 1 mm(2). These sensors show a sensitivity of -56.7 ± 1.3 mV/pH, in a wide pH range of 9 to 5. A proof of concept is also demonstrated using a flexible reference electrode in solid electrolyte with a curved surface. A good balance between the performance parameters (sensitivity), the production costs, and simplicity of the sensors was accomplished, as required for wearable biomedical devices.

An efficient mathematical strategy in the field of solution processed electrochromic (EC) films is outlined as a combination of an experimental work, modeling, and information extraction from massive computational data via statistical software. Design of Experiment (DOE) was used for statistical multivariate analysis and prediction of mixtures through a multiple regression model, as well as the optimization of a five-component sol-gel precursor subjected to complex constraints. This approach significantly reduces the number of experiments to be realized, from 162 in the full factorial (L=3) and 72 in the extreme vertices (D=2) approach down to only 30 runs, while still maintaining a high accuracy of the analysis. By carrying out a finite number of experiments, the empirical modeling in this study shows reasonably good prediction ability in terms of the overall EC performance. An optimized ink formulation was employed in a prototype of a passive EC matrix fabricated in order to test and trial this optically active material system together with a solid-state electrolyte for the prospective application in EC displays. Coupling of DOE with chromogenic material formulation shows the potential to maximize the capabilities of these systems and ensures increased productivity in many potential solution-processed electrochemical applications.