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Flexible electronics is a new paradigm with strong implications from healthcare to energy applications. In this context, electrically conductive polymers are the critical components. Here, we report the design, formation mechanism, and applications of a polymer nanocomposite obtained by single-step laser integration of functionalized graphene into a polymer matrix. Laser processing manipulates the physical-chemical properties of this nanocomposite in a controlled and straightforward way, tuning the electrical resistance from a dielectric (MΩ sq−1) to a highly conductive material (Ω sq−1). We combine experimental and computational approaches to elucidate graphene nanocomposite's nature and formation mechanism, evidencing different processes from photothermal polymer melting to shock wave mixing in a liquid phase within a millisecond time scale. We exploit these fundamental insights on the graphene/polymer nanocomposite in the design and fabrication of electrochemical sensing and antenna devices, showing the potential for healthcare and the Internet of Things.

Glass electronics inspire the emergence of smart functional surfaces. To evolve this concept to the next level, developing new strategies for scalable, inexpensive, and electrically conductive glass-based robust nanocomposites is crucial. Graphene is an attractive material as a conductive filler; however, integrating it firmly into a glass with no energy-intensive sintering, melting, or harsh chemicals has not been possible until now. Moreover, these methods have very limited capability for fabricating robust patterns for electronic circuits. In this work, a conductive (160 OΩ sq

Highly-oriented pyrolytic graphite (HOPG), i.e., the 3D stack of sp2-hybridized carbon sheets, is an attractive material thanks to its high electrical conductivity, chemical inertness, thermal stability, atomic-scale flatness, and ease of exfoliation. Despite an apparently ideal and uniform material, freshly cleaved HOPG shows domains in Kelvin probe force microscopy (KPFM) with surface potential contrast over 30 mV. We systematically investigated these domains using an integrated approach, including time-dependent KPFM and hyperspectral Raman imaging. The observed time-evolving domains are attributed to locally different hydrocarbon adsorption from the environment, driven by structural defects likely related to rotational mismatch, i.e., twisted layers. These defects affect the interlayer coupling between topmost graphene and the underlying layers. Our hypothesis was supported by Raman spectroscopy results, showing domains with G peak shifts and 2D line shape compatible with bilayer graphene. We attribute the selective sensitivity of our Raman spectroscopy results to the top graphene layers as resonances due to van Hove singularities. Our results show that the chemical and electrical properties of HOPG are far more complex than what is generally believed due to the broken symmetry at the top surface, giving rise to graphene bilayer-like behavior.

Two-dimensional (2D) materials have been utilized to design flexible field-effect transistors (FETs) with promising performance. However, flexible FETs still face challenges with poor switching features and ultra-low drive current. In this paper, a facile and repeatable large-area integration process is presented for inkjet-printed FETs with 2D materials active channels and PI films as gate dielectrics. The MoS2 FETs reported here exhibit n-type channel feature with an outstanding average subthreshold swing of 75 mV/dec, an on-state/off-state current ratio of 104, and on-state current up to 10 μA at a power supply voltage of 3.0 V. Besides, MoS2–rGO FETs also exhibit n-type semiconductor features with good electrical properties by the inkjet-printing technology.

All-inkjet-printing of transistors has received much attention for low cost and flexible integrated circuits. However, most flexible field-effect transistors (FETs) based on the emerging two-dimensional materials suffer from the high cost of substrate and electrode materials. The requirements for high-temperature synthesis and precise control in processing add another layer of complexity. To overcome these issues, low-cost flexible paper-based MoS2 FETs were fabricated by inkjet printing of MoS2 channel materials on paper. Additionally, we proposed and achieved the mask-less and low-temperature formation of source and drain electrodes on paper using in-situ selective-area copper reduction. A low sub-threshold swing of 80 mV/dec, high on/off ratio of 105, and very high turn-on current (Ion) of 200 μA of the paper-based flexible MoS2 FETs were demonstrated using the proposed low-cost and facile all-inkjet-printing technique. The all-inkjet-printing technique assisted by in-situ copper reduction opens new opportunities for low-cost and batch fabrication of paper-based electronic devices in ambient conditions.

One of the lessons we learned from the COVID-19 pandemic is that the need for ultrasensitive detection systems is now more critical than ever. While sensors' sensitivity, portability, selectivity, and low cost are crucial, new ways to couple synergistic methods enable the highest performance levels. This review article critically discusses the synergetic combinations of optical and electrochemical methods. We also discuss three key application fields-energy, biomedicine, and environment. Finally, we selected the most promising approaches and examples, the open challenges in sensing, and ways to overcome them. We expect this work to set a clear reference for developing and understanding strategies, pros and cons of different combinations of electrochemical and optical sensors integrated into a single device.

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Graphitic carbon nitride (gCN) has a broad range of promising applications, from energy harvesting and storage to sensing. However, most of the applications are still restricted due to gCN poor dispersibility and limited functional groups. Herein, a direct photografting of gCN using various polymer brushes with tailorable functionalities via UV photopolymerization at ambient conditions is demonstrated. The systematic study of polymer brush-functionalized gCN reveals that the polymerization did not alter the inherent structure of gCN. Compared to the pristine gCN, the gCN-polymer composites show good dispersibility in various solvents such as water, ethanol, and tetrahydrofuran (THF). Patterned polymer brushes on gCN can be realized by employing photomask and microcontact printing technology. The polymer brushes with incorporated silver nanoparticles (AgNPs) on gCN can act as a multifunctional recyclable active sensing layer for surface-enhanced Raman spectroscopy (SERS) detection and photocatalysis. This multifunctionality is shown in consecutive cycles of SERS and photocatalytic degradation processes that can be applied to in situ monitor pollutants, such as dyes or pharmaceutical waste, with high chemical sensitivity as well as to water remediation. This dual functionality provides a significant advantage to our AgNPs/polymer-gCN with regard to state-of-the-art systems reported so far that only allow SERS pollutant detection but not their decomposition. These results may provide a new methodology for the covalent functionalization of gCN and may enable new applications in the field of catalysis, biosensors, and, most interestingly, environmental remediation.

Carbon nanomaterials, especially graphene, are promising due to their abundance and the possibility to exploit them in lightweight, flexible, and wearable electronics enabling paradigms such as the Internet of Things. However, conventional methods to synthesize and integrate graphene into functional materials and flexible devices are either hazardous, time demanding, or excessively energy-consuming. To overcome these issues, here we propose a new concept based on the laser processing of single-layer diazonium-functionalized graphene. This is a safe, inexpensive, and environmentally-friendly method making it a competitive alternative for graphene-device fabrication. Flexible chemiresistors exhibit sensitivity for breath (water vapor and CO2) and ethanol detection up to 1500% higher than laser-reduced graphene oxide devices. We attribute this enhanced sensitivity to an optimal balance between structural defects and electrical conductivity. Flexible electronic circuits demonstrate a superb resilience against scratching and high current stability up to 98% with durability against 180° bending cycles for continuous operation of several weeks. This work can impact biomedical technology and electronics where tunable electrical conductivity, sensitivity, and mechanical stability are of uttermost importance.

Metallized polyimide (PI) film has great applications in the field of flexible electronics. Surface property adjustment is considered as an effective way to realize the metallization of PI film by chemical methods. In this work, we demonstrate a facile approach to fabricate metallized PI film via surface modification and electroless plating. Polyethyleneimine (PEI) cross-linked with glutaraldehyde (GA) is used as a modifier to act on the surface of alkali-treated PI film, and a special regular morphology is obtained. This PEI-modified PI film possesses not only functional groups for chemical bonding but also large surface roughness for mechanical locking with metallic copper layer. The resulting copper layer has low resistivity (2.30 μΩ·cm) and satisfactory adhesion to PI film (the highest score of 5B according to ASTM D3359), and the metallized PI sample exhibits reliable flexibility. These results demonstrate a promising potential of this approach in the field of PI film metallization with impact in wearables, light-weight, and flexible electronics.

Agricultural monitoring is required to enhance crop production, control plant stress, and predict pests and crop infection. Apart from monitoring the external influences, the state of the plant itself must be tracked. However, the modern methods for plant analysis are expensive and require plants processing often in a destructive way. Optical spectroscopy can be used for the non-invasive monitoring requiring no consumables, and little to none sample preparation. In this context, we found that the red beet growth can be monitored by Raman spectroscopy. Our analysis shows that, as plants age, the rate of betalain content increases. This increase makes betalain dominate the whole Raman spectra over other plant components. The dominance of betalain facilitates its use as a molecular marker for plant growth. This finding has implications in the understanding of plant physiology, particularly important for greenhouse growth and the optimization of external conditions such as artificial illumination.

With the continuous growth of the human population and new challenges in the quality of life, it is more important than ever to diagnose diseases and pathologies with high accuracy, sensitivity and in different scenarios from medical implants to the operation room. Although conventional methods of diagnosis revolutionized healthcare, alternative analytical methods are making their way out of academic labs into clinics. In this regard, surface-enhanced Raman spectroscopy (SERS) developed immensely with its capability to achieve single-molecule sensitivity and high-specificity in the last two decades, and now it is well on its way to join the arsenal of physicians. This review discusses how SERS is becoming an essential tool for the clinical investigation of pathologies including inflammation, infections, necrosis/apoptosis, hypoxia, and tumors. We critically discuss the strategies reported so far in nanoparticle assembly, functionalization, non-metallic substrates, colloidal solutions and how these techniques improve SERS characteristics during pathology diagnoses like sensitivity, selectivity, and detection limit. Moreover, it is crucial to introduce the most recent developments and future perspectives of SERS as a biomedical analytical method. We finally discuss the challenges that remain as bottlenecks for a routine SERS implementation in the medical room from in vitro to in vivo applications. The review showcases the adaptability and versatility of SERS to resolve pathological processes by covering various experimental and analytical methods and the specific spectral features and analysis results achieved by these methods.

Raman spectroscopy is the tool of choice in the physicochemical investigation of carbon nanomaterials. However, Raman analysis of graphene oxide (GO) is lagging in comparison to the rich information gained in the case of carbon nanotubes and graphene. Here, we carried out a joint current sensing atomic force microscopy (CSAFM) and Raman spectroscopy investigation of laser-reduced GO. Reduced graphene oxide (rGO) was obtained under different laser powers in the range from 0.1 to 10 mW (532 nm). We compare the Raman spectra and the electrical conductivity at the nanoscale obtained by current sensing atomic force microscopy. Our analysis shows that three bands in the second-order region (2D, D + G, 2G), in the range from 2500 to 3200 cm-1, are uniquely sensitive to the degree of reduction. Moreover, we found that the changes in peak area ratios AD+G/AD and A2G/AD show a direct correlation with the electrical resistance of rGO. We establish an optical micro-spectroscopy way to assess the degree of reduction in laser-reduced GO. These new insights provide a convenient and useful way to investigate the reduction of rGO from the fitting analysis of Raman spectra, becoming a useful tool in fundamental research and the development of rGO-based microdevices.

Graphene oxide (GO) films are deposited on flexible Kapton substrates and selectively modified to conductive reduced graphene oxide (rGO) electrodes using laser patterning. Based on this, we design, fabricate, and test a flexible sensor integrating laser-reduced GO with silver plasmonic nanostructures. The fabricated device results in dual transduction channels: for electrochemical and plasmonic nanostructure-based surface-enhanced Raman spectroscopy (SERS) detection. The spectroscopic analysis verifying the formation of rGO and the modification by silver nanostructures is performed by Raman, energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The morphological investigation is followed by optical and scanning electron microscopy imaging. In addition to pristine silver nanostructures, the Raman spectroscopy results show the formation of species such as Ag2O, Ag2CO3, and Ag2SOx. A dual-channel sensor device based on electrochemical and plasmonic detection is fabricated as a demonstration of our Ag-rGO flexible concept architecture. The dual-channel device performance is successfully demonstrated in the electrochemical and SERS detection of 4-nitrobenzenethiol (4-NBT) using the same device. Our results show that without Ag nanostructures the sensitivity in the electrochemical and optical channels is not sufficient to detect 4-NBT. The performance and stability of the silver modified device are also verified. This work demonstrates an inexpensive, highly efficient, and greener way that is compatible with solution-processing technology for the production of flexible GO-based electrochemical and SERS detection devices integrated with plasmonic nanostructures.

We present the first demonstration of bioelectrodes made from laser-reduced graphene oxide (rGO) on flexible polyethylene terephthalate (PET) substrates that overcome two main issues: using hydrogel on skin interface with standard Ag/AgCl bioelectrodes vs. low signal to noise ratio with capacitance or dry electrodes. Today we develop a dry rGO bioelectrode technology with long-term stability for 100 h in harsh environments and when in contact with skin. Reliability tests in different buffer solutions with pH from 4.8 to 9.2 tested over 24 h showed the robustness of rGO electrodes. In terms of signal to noise ratio, our bioelectrodes performance is comparable to that of commercial ones. The bioelectrodes demonstrate an excellent signal to noise ratio, with a signal match of over 98% with respect to state-of-the-art electrodes used as a benchmark. We attribute the unique stability of our bioelectrodes to the rGO/PET interface modification and composite formation during laser processing used for GO reduction. The rGO/PET composite formation assertion is confirmed by mechanical stripping experiments and visual examination of re-exposed PET. The method developed here is simple, cost-effective, maskless, and can be scaled-up, allowing sustainable manufacture of arbitrary-shaped flexible electrodes for biomedical sensors and wearables.

In this work, we aimed at investigating how good or bad aluminum (Al) and copper (Cu) perform in plasmonic applications as compared to silver (Ag) and gold (Au). Contrary to our expectations, and to widely accepted misconceptions, our experimental and simulation results show that Cu and Al layers on nanospheres make efficient nanostructures for surface-enhanced Raman spectroscopy. In an unprecedented one-to-one comparison among all metal nanostructures, it is demonstrated that Al and Cu rival the conventionally used materials, Ag and Au, displaying similar enhancement. The enhancement capability was shown with the metal nanostructures exposed to air under room conditions showing that the oxide layers formed on Al and Cu do not affect their SERS performance significantly. This concise report further supports large-scale chemical sensing applications using low-cost metals compatible with mass-production fabrication in microelectronics as well as demonstrating an appropriate way to compare the electric field enhancement of different plasmonic materials.

For quite a long time, people thought of the diffraction limit of light as a fundamental unbreakable barrier that prevents seeing objects with sizes smaller than half the wavelength of light. Super-resolution optical methods and near-field optics enabled overcoming this limitation. Here we report an alternative approach based on tracking the photothermal expansion that a nano-object experiences upon visible light absorption, applied successfully in the characterization of samples with a spatial/lateral resolution down to 4 nm. Our device consists of an atomic force microscope coupled with a solid-state laser and a mechanical chopper synchronized with the natural oscillation mode of an in-house-made gold tip cantilever system. This configuration enhances the detection of nanostructures due to the intermittent light excitation and the consequent intermittent thermal expansion of the sample under investigation. The sensitivity and spatial resolution are further improved by the electric field enhancement due ...

Amorphous Cd-doped As 2 Se 3 films with nominal Cd contents up to 12 at.% were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with surface roughnesses below 1 nm, independent of the Cd content. As shown by energy-dispersive X-ray spectroscopy, the Cd content in the film reveals a strong gradient and decreases with the film depth. For heavily Cd-doped (above 7 at.%) As 2 Se 3 films, Raman features attributed to CdSe longitudinal optical (LO) phonon and its overtone (2LO) are revealed in the Raman spectra as an evidence for the formation of CdSe nanocrystallites in the As 2 Se 3 :Cd film under above-bandgap or below-bandgap laser illumination. The CdSe nanocrystallites undergo tensile strain due to a photoplastic effect in the As 2 Se 3 film, i. e. partial removal of the material from the laser spot. The tensile strain value, estimated from the LO phonon frequency shift, is shown to reach nearly 2 GPa.

MXenes are a novel two-dimensional material family composed of transition metal carbides and carbonitrides that show promising performances in many applications. The intrinsic properties of MXenes are required to develop in different directions with the broadening applications. However, their properties are determined in the synthesis stage and are affected by various factors, such as precursor MAX phase, etchant, reaction time, and temperature. Since these parameters are difficult to control precisely, the targeted design of MXenes properties remains an open challenge. Herein, the post-processing modification of MXenes comes into play as a route to easily and efficiently tune and optimize their properties. This review critically discusses the research progress of MXenes’ post-processing approaches to bridge the gap between theoretical predictions and properties observed experimentally. These strategies include atomic doping, functional group modification, and compounding with other materials, focusing on engineering electrical properties, mechanical properties, chemical stability, and the hydrophilic-hydrophobic nature of MXenes. We thus aim at providing a reference for customizing MXenes with targeted functionalities essential for future applications.

The covalent attachment of one dimensional (1D) polymer brush onto a two-dimensional (2D) material presents an appealing strategy to fabricate anisotropic polymer membranes, namely “polymer carpets”. Conductive polymer carpets that are based on graphene and conductive polymers are especially interesting due to their potential in microelectronics, actuators and optoelectronics. Here we describe a versatile method for the covalent grafting of the poly(3-hexylthiophene) (P3HT) brush onto large area graphene to fabricate conductive polymer carpets through a combination of photografting polymerization and Kumada catalyst transfer polycondensation (KCTP) to grow P3HT (up to 260 nm) on single layer graphene forming conductive polymer carpets (i.e. G-PS-P3HT). Raman mapping revealed that the grafting reactions occurred on native graphene defects, without deteriorating the conjugation plane of graphene. The advanced architecture of G-PS-P3HT resulted in a high photocurrent (ca. 0.3 mA cm−2) under light irradiation in a junction with MoS2 to form efficient an p–n heterostructure, with promising potential in optoelectronics.

Tip-enhanced Raman spectroscopy (TERS) allows the chemical analysis with a spatial resolution at the nanoscale, well beyond what the diffraction limit of light makes possible. We can further boost the TERS sensitivity by using a metallic substrate in the so-called gap-mode TERS. In this context, the goal of this work is to provide a generalized view of imaging artifacts in TERS and near-field imaging that occur due to tip-sample coupling. Contrary to the case of gap-mode with a flat substrate where the size of the enhanced region is smaller than the tip size when visualizing 3D nanostructures the tip convolution effect may broaden the observed dimensions due to the local curvature of the sample. This effect is particularly critical considering that most works on gap-mode TERS consider a perfectly flat substrate which is rarely the case in actual experiments. We investigate a range of substrates to evidence these geometrical effects and to obtain an understanding of the nanoscale curvature role in TERS imaging. Our experimental results are complemented by numerical simulations and an analogy with atomic force microscopy artifacts is introduced. As a result, this work offers a useful analysis of gap-mode TERS imaging with tip- and substrate-related artifacts furthering our understanding and the reliability of near-field optical nanospectroscopy.

Electrochemical sensors play a significant role in detecting chemical ions, molecules, and pathogens in water and other applications. These sensors are sensitive, portable, fast, inexpensive, and suitable for online and in-situ measurements compared to other methods. They can provide the detection for any compound that can undergo certain transformations within a potential window. It enables applications in multiple ion detection, mainly since these sensors are primarily non-specific. In this paper, we provide a survey of electrochemical sensors for the detection of water contaminants, i.e., pesticides, nitrate, nitrite, phosphorus, water hardeners, disinfectant, and other emergent contaminants (phenol, estrogen, gallic acid etc.). We focus on the influence of surface modification of the working electrodes by carbon nanomaterials, metallic nanostructures, imprinted polymers and evaluate the corresponding sensing performance. Especially for pesticides, which are challenging and need special care, we highlight biosensors, such as enzymatic sensors, immunobiosensor, aptasensors, and biomimetic sensors. We discuss the sensors’ overall performance, especially concerning real-sample performance and the capability for actual field application.

Silicon and silicon nitride metal-coated cantilevers have been in use for a long time in several scanning probe microscopy applications that require electrically conductive probes. However, conventional metalized cantilevers present several drawbacks such as limited life-time of the metal layer due to wear, and increased tip radius. This work focuses on monolithic metallic cantilevers developed in order to overcome the limitations of conventional metalized atomic force microscopy (AFM) probes. These custom-made cantilevers are designed for several applications such as in current-sensing AFM (CSAFM), Kelvin probe force microscopy (KPFM), and tip-enhanced Raman spectroscopy (TERS). Determination of the dynamic and static mechanical properties of these cantilevers in a non-destructive way is reported here. Key parameters under investigation are the cantilever spring constant and the frequency response using finite element method (FEM). Gold cantilevers are selected for this study, which allow optimizing the design and the process of developing these metallic cantilevers with parameters engineered for the applications mentioned above. This work contributes to the establishment and applicability of custom-made probes in advanced scanning probe microscopy methods and their performance understanding using computer simulations.

Here we present the results on an investigation of resonant Stokes and anti- Stokes surface-enhanced Raman scattering (SERS) by optical phonons in colloidal CdSe nanocrystals (NCs) homogeneously deposited on arrays of Au nanoclusters using the Langmuir–Blodgett technology. The thickness of deposited NCs, determined by transmission and scanning electron microscopy, amounts to approximately 1 monolayer. Special attention is paid to the determination of the localized surface plasmon resonance (LSPR) energy in the arrays of Au nanoclusters as a function of the nanocluster size by means of micro-ellipsometry. SERS by optical phonons in CdSe NCs shows a significant enhancement factor with a maximal value of 2 × 103 which depends resonantly on the Au nanocluster size and thus on the LSPR energy. The deposition of CdSe NCs on the arrays of Au nanocluster dimers enabled us to study the polarization dependence of SERS. It was found that a maximal SERS signal is observed for the light polarization along the dimer axis. Finally, SERS by optical phonons was observed for CdSe NCs deposited on the structures with a single Au dimer. A difference of the LO phonon energy is observed for CdSe NCs on different single dimers. This effect is explained as the confinement-induced shift which depends on the CdSe nanocrystal size and indicates quasi-single NC Raman spectra being obtained.

Sensitivity and versatility are characteristics that make a sensor device attractive for wide-spread applications in everyday life. Surface-enhanced Raman spectroscopy (SERS) is capable of providing the highest sensitivity, that of single-molecule detection, and excellent specificity due to its fingerprinting capability. However, conventional SERS substrates must be optimized to operate for a particular excitation wavelength. Here in this work, we achieve for the first time multiwavelength amplification with a hybrid plasmonic/photonic heterostructure integrating a gradient photonic crystal and an Ag nanotriangle array. We demonstrate the detection of ultrathin molecular layers showing a signal amplification for the typical laser wavelengths used in Raman spectroscopy detection. By combining photonics and plasmonics in a single silicon chip, we expand multiwavelength- and spatially-selective ultra-sensitive detection to a wide range of applications from biomedicine to safety.

Dimethoate (DMT) is an organophosphate pesticide (OP), which is widely used against insects and mites and their control in agriculture. As other OPs, DMT is also an inhibitor of acetylcholinesterase, which is responsible for the disabling of cholinesterase required for the functioning of the central nervous system. This pesticide can invade living cells of the human body through contact or ingestion. We report an electrochemical sensor based on a layer by layer deposition of PDAC/GO on silver electrodes. The sensor fabrication, physical characterization i.e. Raman spectroscopy and scanning electron microscopy of PDAC/GO based films, and its electrochemical characterization are discussed. The detection of DMT by analyzing electrochemical measurements including cyclic voltammetry and impedance spectroscopy shows that functionalization using layer by layer deposition improves electrochemical response and presents a basis for detection of DMT. The highest response is observed in the case of only one PDAC/GO layer which is attributed to the properly balanced interaction between DMT and PDAC/GO layer, and the increase of electrical resistivity of the PDAC/GO layer with its thickness. © 2019 IEEE. Conference of 16th International Multi-Conference on Systems, Signals and Devices, SSD 2019 ; Conference Date: 21 March 2019 Through 24 March 2019; Conference Code:154292

Extensive use of pesticides and their accumulation in the environment requires swift actions in terms of their removal, detection, and quantification. Currently, golden standard methods used for quantification of pesticides require expensive instrumentation and are not suitable for quick measurements outside of properly equipped laboratory. Here we investigate the detection of dimethoate (DMT) using PDAC/reduced graphene oxide (rGO)-modified Ag electrodes. The sensor performance depends on the temperature used for the reduction of graphene oxide (GO) in PDAC/GO bi-layer on Ag electrode. Using this combination of nanomaterials, we show the quantification of DMT with either voltammetry or impedance spectroscopies. The former approach relies on direct electrochemical transformations of DMT which are observed at relatively high anodic potential around 0.3 V vs. saturated calomel electrode. Impedance spectroscopy shows complex behavior with increasing DMT concentration, but seems to be rather sensitive to low DMT concentrations. These results present a possible direction to the development of highly efficient electrochemical sensors for pesticide detection. © 2019 IEEE.

The present study covers the nanoanalysis methods for four key material characteristics: electrical and electronic properties, optical, stress and strain, and chemical composition. With the downsizing of the geometrical dimensions of the electronic, optoelectronic, and electromechanical devices from the micro to the nanoscale and the simultaneous increase in the functionality density, the previous generation of microanalysis methods is no longer sufficient. Therefore, the metrology of materials' properties with nanoscale resolution is a prerequisite in materials' research and development. The article reviews the standard analysis methods and focuses on the advanced methods with a nanoscale spatial resolution based on atomic force microscopy (AFM): current-sensing AFM (CS-AFM), Kelvin probe force microscopy (KPFM), and hybrid optical techniques coupled with AFM including tip-enhanced Raman spectroscopy (TERS), photothermal-induced resonance (PTIR) characterization method s (nano-Vis, nano-IR), and photo-induced force microscopy (PIFM). The simultaneous acquisition of multiple parameters (topography, charge and conductivity, stress and strain, and chemical composition) at the nanoscale is a key for exploring new research on structure-property relationships of nanostructured materials, such as carbon nanotubes (CNTs) and nano/microelectromechanical systems (N/MEMS). Advanced nanocharacterization techniques foster the design and development of new functional materials for flexible hybrid and smart applications.

The polymer scaffolds surfaces are inherently hydrophobic what limits its performance as implants and compatibility with human tissue essential for such applications as tissue engineering, nerve regeneration, drug delivery, etc. The plasma treatment was demonstrated to change the wetting properties of scaffolds making them hydrophilic. However, that is not a lasting effect. In this work, we aim at addressing this problem with systematic time-stability investigation of scaffolds functionalized with graphene oxide (GO) layers. To this end, we used several polymers including polycaprolactone (PCL), poly-L-lactic acid (PLLA), l -lactide-co-glycolide copolymer (PLGA) and l -lactide-co-caprolactone copolymer (PLC) functionalized with GO, evaluating also control samples without any treatment and treated by plasma. Our results demonstrate that the GO coating provides a successful and stable hydrophilic functionality to all polymer scaffolds here investigated. Contrary to plasma treatment used as a reference for the surface-wettability provider, only the GO effects remain stable for extended periods of up to 30 days. This work contributes to the robust application of graphene-functionalized polymer scaffolds with long lifetime hydrophilicity.

Efficient substrates for surface-enhanced Raman spectroscopy (SERS) are under constant development, since time-consuming and costly fabrication routines are often an issue for high-throughput spectroscopy applications. In this research, we use a two-step fabrication method to produce self-organized parallel-oriented plasmonic gold nanostructures. The fabrication routine is ready for wafer-scale production involving only low-energy ion beam irradiation and metal deposition. The optical spectroscopy features of the resulting structures show a successful bidirectional plasmonic response. The localized surface plasmon resonances (LSPRs) of each direction are independent from each other and can be tuned by the fabrication parameters. This ability to tune the LSPR characteristics allows the development of optimized plasmonic nanostructures to match different laser excitations and optical transitions for any arbitrary analyte. Moreover, in this study, we probe the polarization and wavelength dependence of such bidirectional plasmonic nanostructures by a complementary spectroscopic ellipsometry and Raman spectroscopy analysis. We observe a significant signal amplification by the SERS substrates and determine enhancement factors of over a thousand times. We also perform finite element method-based calculations of the electromagnetic enhancement for the SERS signal provided by the plasmonic nanostructures. The calculations are based on realistic models constructed using the same particle sizes and shapes experimentally determined by scanning electron microscopy. The spatial distribution of electric field enhancement shows some dispersion in the LSPR, which is a direct consequence of the semi-random distribution of hotspots. The signal enhancement is highly efficient, making our SERS substrates attractive candidates for high-throughput chemical sensing applications in which directionality, chemical stability, and large-scale fabrication are essential requirements.