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A significant challenge in creating supramolecular materials is that conjugating molecular functionalities to building blocks often results in dissociation or undesired morphological transformation of their assemblies. Here we present a facile strategy to preserve structurally labile peptide assemblies after molecular modification of the self‐assembling peptides. Sheet‐forming peptides are designed to afford a staggered alignment with the segments bearing chemical modification sites protruding from the sheet surfaces. The staggered assembly allows for simultaneous separation of attached molecules from each other and from the underlying assembly motifs. Strikingly, using PEGs as the external molecules, PEG400‐ and PEG700‐peptide conjugates directly self‐associate into nanosheets with the PEG chains localized on the sheet surfaces. In contrast, the sheet formation based on in‐register lateral packing of peptides does not recur upon the peptide PEGylation. This strategy allows for fabrication of densely modified assemblies with a variety of molecules, as demonstrated using biotin (hydrophobic molecule), c(RGDfK) (cyclic pentapeptide), and nucleic acid aptamer (negatively charged ssDNA). The staggered co‐assembly also enables extended tunability of the amount/density of surface molecules, as exemplified by screening ligand‐appended assemblies for cell targeting. This study paves the way for functionalization of historically challenging fragile assemblies while maintaining their overall morphology. [ABSTRACT FROM AUTHOR]

Heavy-metal-free III–V colloidal quantum dots (CQDs) show promise in optoelectronics: Recent advancements in the synthesis of large-diameter indium arsenide (InAs) CQDs provide access to short-wave infrared (IR) wavelengths for three-dimensional ranging and imaging. In early studies, however, we were unable to achieve a rectifying photodiode using CQDs and molybdenum oxide/polymer hole transport layers, as the shallow valence bandedge (5.0 eV) was misaligned with the ionization potentials of the widely used transport layers. This occurred when increasing CQD diameter to decrease the bandgap below 1.1 eV. Here, we develop a rectifying junction among InAs CQD layers, where we use molecular surface modifiers to tune the energy levels of InAs CQDs electrostatically. Previously developed bifunctional dithiol ligands, established for II-VI and IV-VI CQDs, exhibit slow reaction kinetics with III-V surfaces, causing the exchange to fail. We study carboxylate and thiolate binding groups, united with electron-donating free end groups, that shift upward the valence bandedge of InAs CQDs, producing valence band energies as shallow as 4.8 eV. Photophysical studies combined with density functional theory show that carboxylate-based passivants participate in strong bidentate bridging with both In and As on the CQD surface. The tuned CQD layer incorporated into a photodiode structure achieves improved performance with EQE (external quantum efficiency) of 35% (>1 μm) and dark current density < 400 nA cm−2, a >25% increase in EQE and >90% reduced dark current density compared to the reference device. This work represents an advance over previous III-V CQD short-wavelength IR photodetectors (EQE < 5%, dark current > 10,000 nA cm−2). [ABSTRACT FROM AUTHOR]

Microporous carbon membranes with tunable micropores are attractive materials for CO 2 separations. Tailoring the gas transport channels is an effective strategy to achieve high separation performance, while it remains challenging due to the lack of control over sub-nanopores. Herein, we present an in-situ molecular functionalization strategy wherein the confined sub-nanopore properties are designed by enforcing molecules to diffuse over pores and functionalize the pore affinity. By enforcing oxygen-functionalization, a strong CO 2 affinity between the carbon matrix and CO 2 molecules is generated, which facilitated CO 2 transport, thereby enhancing the CO 2 permeability by ∼4.7-fold and without sacrificing molecular sieving ability for gas mixtures, like CO 2 /N 2 and CO 2 /CH 4. The functionalization mechanism was confirmed using reactive force field molecular dynamics (ReaxFF-MD) simulations. Furthermore, this strategy, which was directly applied to hollow fiber membrane modules, provides a facile and scalable approach, and expands the currently limited library of penetrative micropore tailoring of microporous membranes. [Display omitted] • An in-situ molecular functionalization strategy was presented to design the pore properties of CMS membranes. • CO 2 permeability of oxygen-functionalized CMS membranes was increased by 4.6-fold. • The functionalization mechanism was confirmed using ReaxFF-MD simulations. [ABSTRACT FROM AUTHOR]

Developing new functionalities of two-dimensional materials (2Dms) can be achieved by their chemical modification with a broad spectrum of molecules. This functionalization is commonly studied by using spectroscopies such as Raman, IR, or XPS, but the detection limit is a common problem. In addition, these methods lack detailed spatial resolution and cannot provide information about the homogeneity of the coating. Atomic force microscopy (AFM), on the other hand, allows the study of 2Dms on the nanoscale with excellent lateral resolution. AFM has been extensively used for topographic analysis; however, it is also a powerful tool for evaluating other properties far beyond topography such as mechanical ones. Therefore, herein, we show how AFM adhesion mapping of transition metal chalcogenide 2Dms (i.e., MnPS 3 and MoS 2 ) permits a close inspection of the surface chemical properties. Moreover, the analysis of adhesion as relative values allows a simple and robust strategy to distinguish between bare and functionalized layers and significantly improves the reproducibility between measurements. Remarkably, it is also confirmed by statistical analysis that adhesion values do not depend on the thickness of the layers, proving that they are related only to the most superficial part of the materials. In addition, we have implemented an unsupervised classification method using k-means clustering, an artificial intelligence-based algorithm, to automatically classify samples based on adhesion values. These results demonstrate the potential of simple adhesion AFM measurements to inspect the chemical nature of 2Dms and may have implications for the broad scientific community working in the field.

In this paper, we model the electrical properties of germanium nanowires with a particular focus on physical mechanisms of electrical molecular sensing. We use the Tibercad software to solve the drift-diffusion equations in 3D and we validate the model against experimental data, considering a p-doped nanowire with surface traps. We simulate three different types of interactions: (1) Passivation of surface traps; (2) Additional surface charges; (3) Charge transfer from molecules to nanowires. By analyzing simulated I–V characteristics, we observe that: (i) the largest change in current occurs with negative charges on the surfaces; (ii) charge transfer provides relevant current changes only for very high values of additional doping; (iii) for certain values of additional n-doping ambipolar currents could be obtained. The results of these simulations highlight the complexity of the molecular sensing mechanism in nanowires, that depends not only on the NW parameters but also on the properties of the molecules. We expect that these findings will be valuable to extend the knowledge of molecular sensing by germanium nanowires, a fundamental step to develop novel sensors based on these nanostructures.

Despite great interests in electrochemical energy storage systems for numerous applications, considerable challenges remain to be overcome. Among the various approaches to improving the stability, safety, performance, and cost of these systems, molecular functionalization has recently been proved an attractive method that allows the tuning of material surface reactivity while retaining the properties of the bulk material. For this purpose, the reduction of aryldiazonium salt, which is a versatile method, is considered suitable; it forms robust covalent bonds with the material surface, however, with the formation of multilayer structures and sp defects (for carbon substrate) that can be detrimental to the electronic conductivity. Alternatively, non-covalent molecular functionalization based on π- π interactions using aromatic ring units has been proposed. In this review, the various advances in molecular functionalization concerning the current limitations in lithium-ion batteries and electrochemical capacitors are discussed. According to the targeted applications and required properties, both covalent and non-covalent functionalization methods have proved to be very efficient and versatile. Fundamental aspects to achieve a better understanding of the functionalization reactions as well as molecular layer properties and their effects on the electrochemical performance are also discussed. Finally, perspectives are proposed for future implementation of molecular functionalization in the field of electrochemical storage. [ABSTRACT FROM AUTHOR]

Graphene is a two-dimensional material with remarkable physicochemical characteristics. In particular, graphene is highly sensitive to its electronic and electrostatic environment. For these reasons, among various applications of graphene, its use as a sensitive material in field-effect transistors (FETs) is widely studied, especially for biodetection purposes. So, this review aims to introduce the reader to the state of the art of graphene-based materials for their applications in electrolyte-gated graphene field-effect transistors (EGGFETs) for biosensing applications. Among numerous ways to produce graphene-based materials for such devices, some of the most important, widely used methods are presented herein. After that, the working principle of graphene-based FETs is discussed and the various ways to tune graphene's electronic properties are presented. The fabrication methods are discussed, with an emphasis on inkjet printing which allows printing of EGGFETs from aqueous graphene oxide inks, providing that it is subsequently reduced to adjust the mobility of charge carriers and the doping state. Finally, some of the recent works concerning the use of FETs in biosensing applications are reviewed. • Various methods of graphene preparation are reviewed, in particular solution-based processes. • The electronic properties of graphene due to its structure, and the way to control these electronic properties. • How to control graphene doping and the position of the charge neutrality point. • Some applications of electrolyte-gated graphene FETs for chemical sensing. [ABSTRACT FROM AUTHOR]

The all-surface nature of two-dimensional (2D) materials renders them highly sensitive to environmental changes, enabling the on-demand tailoring of their physical properties. Transition metal dichalcogenides, such as 2H molybdenum disulfide (MoS 2 ), can be used as a sensory material capable of discriminating molecules possessing a similar structure with a high sensitivity. Among them, the identification of isomers represents an unexplored and challenging case. Here, we demonstrate that chemical functionalization of defect-engineered monolayer MoS 2 enables isomer discrimination via a field-effect transistor readout. A multiscale characterization comprising X-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and electrical measurement corroborated by theoretical calculations revealed that monolayer MoS 2 exhibits exceptional sensitivity to the differences in the dipolar nature of molecules arising from their chemical structure such as the one in difluorobenzenethiol isomers, allowing their precise recognition. Our findings underscore the potential of 2D materials for molecular discrimination purposes, in particular for the identification of complex isomers.

The polar discontinuity at any ferroelectric surface creates a depolarizing field that must be screened for the polarization to be stable. In capacitors, screening is done by the electrodes, while in bare ferroelectric surfaces it is typically accomplished by atmospheric adsorbates. Although chemisorbed species can have even better screening efficiency than conventional electrodes, they are subject to unpredictable environmental fluctuations and, moreover, dominant charged species favor one polarity over the opposite. This paper proposes a new screening concept, namely surface functionalization with resonance-hybrid molecules, which combines the predictability and bipolarity of conventional electrodes with the screening efficiency of adsorbates. Thin films of barium titanate (BaTiO 3 ) coated with resonant para-aminobenzoic acid (pABA) display increased coercivity for both signs of ferroelectric polarization irrespective of the molecular layer thickness, thanks to the ability of these molecules to swap between different electronic configurations and adapt their surface charge density to the screening needs of the ferroelectric underneath. Because electron delocalization is only in the vertical direction, unlike conventional metals, chemical electrodes allow writing localized domains of different polarity underneath the same electrode. In addition, hybrid capacitors composed of graphene/pABA/ferroelectric have been made with enhanced coercivity compared to pure graphene-electode capacitors., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Replacement of Cu interconnects with carbon nanotubes (CNTs) has been hindered by the high resistance of the CNTs. In this paper, methods for reducing CNT interconnect sheet resistance are presented. Functionalization with electron accepting molecules decreased sheet resistance up to 60%, giving a minimum sheet resistance of ∼55 Ω/sq. Alignment of CNTs within the interconnect further reduced resistance. In contrast to nonaligned fabrics, aligned CNT interconnects maintained a constant resistance as CNT line width decreased, demonstrating a path for scaling to smaller technology nodes. In addition, interconnects made with single-walled CNTs consistently showed lower resistance than those with multiwalled CNTs. Finally, a projected RC delay was calculated that demonstrates improved performance below the 45 nm technology node for CNTs compared to Cu. To achieve the desired RC delay improvement, the aspect ratio of the CNT interconnect should be scaled appropriately and combined with an additional reduction in CNT interconnect sheet resistance to 10 Ω/sq, which is feasible based on the functionalization and alignment methods presented here. [ABSTRACT FROM PUBLISHER]

In this paper, we model the electrical properties of germanium nanowires with a particular focus on physical mechanisms of electrical molecular sensing. We use the Tibercad software to solve the drift-diffusion equations in 3D and we validate the model against experimental data, considering a p-doped nanowire with surface traps. We simulate three different types of interactions: (1) Passivation of surface traps; (2) Additional surface charges; (3) Charge transfer from molecules to nanowires. By analyzing simulated I–V characteristics, we observe that: (i) the largest change in current occurs with negative charges on the surfaces; (ii) charge transfer provides relevant current changes only for very high values of additional doping; (iii) for certain values of additional n-doping ambipolar currents could be obtained. The results of these simulations highlight the complexity of the molecular sensing mechanism in nanowires, that depends not only on the NW parameters but also on the properties of the molecules. We expect that these findings will be valuable to extend the knowledge of molecular sensing by germanium nanowires, a fundamental step to develop novel sensors based on these nanostructures. [ABSTRACT FROM AUTHOR]

WSe 2 is a layered ambipolar semiconductor enabling hole and electron transport, which renders it a suitable active component for logic circuitry. However, solid-state devices based on single- and bilayer WSe 2 typically exhibit unipolar transport and poor electrical performance when conventional SiO 2 dielectric and Au electrodes are used. Here, we show that silane-containing functional molecules form ordered monolayers on the top of the WSe 2 surface, thereby boosting its electrical performance in single- and bilayer field-effect transistors. In particular, by employing SiO 2 dielectric substrates and top Au electrodes, we measure unipolar mobility as high as μ h = 150 cm 2 V -1 s -1 and μ e = 17.9 cm 2 V -1 s -1 in WSe 2 single-layer devices when ad hoc molecular monolayers are chosen. Additionally, by asymmetric double-side functionalization with two different molecules, we provide opposite polarity to the top and bottom layer of bilayer WSe 2 , demonstrating nearly balanced ambipolarity at the bilayer limit. Our results indicate that the controlled functionalization of the two sides of the WSe 2 mono- and bilayer flakes with highly ordered molecular monolayers offers the possibility to simultaneously achieve energy level engineering and defect functionalization, representing a path toward deterministic control over charge transport in 2D materials.