RESUMO
Small-molecule analyte detection is key for improving quality of life, particularly in health monitoring through the early detection of diseases. However, detecting specific markers in complex multicomponent media using devices compatible with point-of-care (PoC) technologies is still a major challenge. Here, we introduce a novel approach that combines molecularly imprinted polymers (MIPs), electrolyte-gated transistors (EGTs) based on 2D materials, and machine learning (ML) to detect hippuric acid (HA) in artificial urine, being a critical marker for toluene intoxication, parasitic infections, and kidney and bowel inflammation. Reduced graphene oxide (rGO) was used as the sensory material and molecularly imprinted polymer (MIP) as supramolecular receptors. Employing supervised ML techniques based on symbolic regression and compressive sensing enabled us to comprehensively analyze the EGT transfer curves, eliminating the need for arbitrary signal selection and allowing a multivariate analysis during HA detection. The resulting device displayed simultaneously low operating voltages (<0.5 V), rapid response times (≤10 s), operation across a wide range of HA concentrations (from 0.05 to 200 nmol L-1), and a low limit of detection (LoD) of 39 pmol L-1. Thanks to the ML multivariate analysis, we achieved a 2.5-fold increase in the device sensitivity (1.007 µA/nmol L-1) with respect to the human data analysis (0.388 µA/nmol L-1). Our method represents a major advance in PoC technologies, by enabling the accurate determination of small-molecule markers in complex media via the combination of ML analysis, supramolecular analyte recognition, and electrolytic transistors.
RESUMO
Organic diodes and molecular rectifiers are fundamental electronic devices that share one common feature: current rectification ability. Since both present distinct spatial dimensions and working principles, the rectification of organic diodes is usually achieved by interface engineering, while changes in molecular structures commonly control the molecular rectifiers' features. Here, we report on the first observation of temperature-driven inversion of the rectification direction (IRD) in ensemble molecular diodes (EMDs) prepared in a vertical stack configuration. The EMDs are composed of 20 nm thick molecular ensembles of copper phthalocyanine in close contact with one of its fluorinated derivatives. The material interface was found to be responsible for modifying the junction's conduction mechanisms from nearly activationless transport to Poole-Frenkel emission and phonon-assisted tunneling. In this context, the current rectification was found to be dependent on the interplay of such distinct charge transport mechanisms. The temperature has played a crucial role in each charge transport transition, which we have investigated via electrical measurements and band diagram analysis, thus providing the fundamentals on the IRD occurrence. Our findings represent an important step towards simple and rational control of rectification in carbon-based electronic nanodevices.
RESUMO
Nanomembranes (NMs) are freestanding structures with few-nanometer thickness and lateral dimensions up to the microscale. In nanoelectronics, NMs have been used to promote reliable electrical contacts with distinct nanomaterials, such as molecules, quantum dots, and nanowires, as well as to support the comprehension of the condensed matter down to the nanoscale. Here, we propose a tunable device architecture that is capable of deterministically changing both the contact geometry and the current injection in nanoscale electronic junctions. The device is based on a hybrid arrangement that joins metallic NMs and molecular ensembles, resulting in a versatile, mechanically compliant element. Such a feature allows the devices to accommodate a mechanical stimulus applied over the top electrodes, enlarging the junctions' active area without compromising the molecules. A model derived from the Hertzian mechanics is employed to correlate the contact dynamics with the electronic transport in these novel devices denominated as variable-area transport junctions (VATJs). As a proof of concept, we propose a direct application of the VATJs as compression gauges envisioning the development of hypersensitive pressure pixels. Regarding sensitivity (â¼480 kPa-1), the VATJ-based transducers constitute a breakthrough in nanoelectronics, with the prospect of carrying its sister-field of molecular electronics out of the laboratory via integrative, hybrid organic/inorganic nanotechnology.