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The development of hybrid nanostructures of graphene oxide (GO) and metal nanoparticles (NPs) is of paramount interest for highly flexible surface-enhanced Raman scattering (SERS) substrate-based molecular sensing. In this work, we report a simple and eco-friendly synthesis strategy for the synthesis of a three-dimensional (3D) GO/gold nanostar (3D GO/Au NS) hybrid nanocomposite using deep eutectic solvent (DES) for SERS-based molecular sensing. The 3D GO/Au NS hybrid nanocomposite was obtained by a two-step synthetic process. In the first step, the GO nanosheets of thickness ∼1.25 nm were homogeneously dispersed in choline chloride/urea (molar ratio of 1:2)-derived DES, followed by functionalization of −NH groups using 3aminopropyltriethoxysilane. Afterward, the presynthesized Au NSs of size ranging between 150−200 nm were then covalently attached on the −NH-functionalized GO nanosheets mediated by DES at 60 °C to obtain 3D GO/Au NS hybrid nanocomposites. Importantly, the SERS substrate fabricated using the 3D GO/Au NS hybrid nanocomposite exhibits highly enhanced SERS activity with an enhancement factor of 1.7 × 10 5 and high sensitivity for the detection of crystal violet with a concentration up to 10 −11 M. The green synthetic approach presented here can be expected to be promising for the large-scale fabrication of GO−metal NP-based hybrid nanostructures for their potential applications in SERS-based sensing.

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Ti0.92Ta0.08N and Ti0.41Al0.51Ta0.08N thin films grown on stainless-steel substrates, with no external heating, by hybrid high-power impulse and dc magnetron sputtering (HiPIMS/DCMS), were investigated for corrosion resistance. The Ta target was operated in HiPIMS mode to supply pulsed Ta-ion fluxes, while two Ti (or Ti and Al) targets were operated in DCSM mode in order to provide a high deposition rate. Corrosion resistance was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy employing a 3.5% NaCl solution at room temperature. The 300-nm-thick transition-metal nitride coatings exhibited good corrosion resistance due to film densification resulting from pulsed heavy Ta-ion irradiation during film growth. Corrosion protective efficiencies were above 99.8% for both Ti0.41Al0.51Ta0.08N and Ti0.92Ta0.08N, and pore resistance was apparently four orders of magnitude higher than for bare 304 stainless-steel substrates.

This work was aimed at evaluating the corrosion resistance of multilayer Cr/CrN coatings deposited by the unbalanced magnetron sputtering (UBM) technique. Coatings were produced at room temperature using 400 mA discharge current, 9 sccm argon flow and 3 sccm nitrogen flow. The total thickness of coatings deposited on AISI 304 stainless steel and silicon (100) varied between 0.2 a 3 μm as bilayer period varied between 20 and 200 nm. Coating microstructure and chemical composition was studied through scanning electron microscopy (SEM) and texture and crystalline phases were analysed by X-ray diffraction (XRD) before and after corrosion tests which were carried out by potentiodynamic polarisation using 0.5 M H2SO4 + 0.05M KSCN solution. Lower bilayer period coatings presented better corrosion resistance and their corrosion mechanism is discussed in this article.

CrN/Cr nano-multilayer films grown by using unbalanced magnetron sputtering (UBMS) on 304 stainless-steel (304 ss), varying the bilayer period (ʌ) with 20, 100 and 200 nm, and a total thickness of about 1 µm. In this study, the influence of the bilayer period on the electrochemical properties of these films have been investigated. The corrosion resistance of these films was studied by means of electrochemical impedance spectroscopy (EIS) in a 3.0% NaCl solution at room temperature, varying the immersion time from 1 to 168 of constant immersion. The performance of the CrN/Cr nanomultilayer was enhanced with the period increase, which can be attributed to the formation of a dense passive layer. This multilayer architecture hinds columnar film growth resulting in better corrosion resistance.

In this work, a high-resolution atomic force acoustic microscopy imaging technique is developed in order to obtain the local indentation modulus at the nanoscale level. The technique uses a model that gives a qualitative relationship between a set of contact resonance frequencies and the indentation modulus. It is based on white-noise excitation of the tip–sample interaction and uses system theory for the extraction of the resonance modes. During conventional scanning, for each pixel, the tip–sample interaction is excited with a white-noise signal. Then, a fast Fourier transform is applied to the deflection signal that comes from the photodiodes of the atomic force microscopy (AFM) equipment. This approach allows for the measurement of several vibrational modes in a single step with high frequency resolution, with less computational cost and at a faster speed than other similar techniques. This technique is referred to as stochastic atomic force acoustic microscopy (S-AFAM), and the frequency shifts of the free resonance frequencies of an AFM cantilever are used to determine the mechanical properties of a material. S-AFAM is implemented and compared with a conventional technique (resonance tracking-atomic force acoustic microscopy, RT-AFAM). A sample of a graphite film on a glass substrate is analyzed. S-AFAM can be implemented in any AFM system due to its reduced instrumentation requirements compared to conventional techniques.