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Carbon nanoparticles (CNPs) with high porosity and great optical features can be used as a luminescent material. One year later, the same group investigated the NLO properties CNPs and boron-doped CNPs by 532 nm and 1064 nm laser excitations to uncover the underlying physical mechanisms in their NLO response. Hence, a facile approach, laser ablation technique, was employed for carbon nanoparticles (CNPs) synthesis from suspended activated carbon (AC). Morphological properties of the prepared CNPs were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). UV-Vis and fluorescence (FL) spectra were used to optical properties investigation of CNPs. The size distribution of nanoparticles was evaluated using dynamic light scattering (DLS). The nonlinear optical (NLO) coefficients of the synthesized CNPs were determined by the Z-scan method. As a result, strong reverse saturable absorption and self-defocusing effects were observed at the excitation wavelength of 442 nm laser irradiation. These effects were ascribed to the presence of delocalized π-electrons in AC CNPs. To the best of our knowledge, this is the first study investigating the NLO properties of the AC CNPs. [ABSTRACT FROM AUTHOR]

Low‐dimensional carbon materials occupy a relevant role in the field of nanotechnology. Herein, the authors report a study conducted by atomic force microscopy and Raman spectroscopy on the deposition of carbon dots onto graphene surfaces. The study aims at understanding if and how the morphology and the microstructure of chemical vapor deposited graphene on Si/SiO2 may change due to the interaction with the carbon dots. Potential alteration in the graphene's electrical properties might be detrimental for optoelectronic applications. The deposition of carbon dots dispersed in water and ethanol solvents are explored to investigate the effect of solvents with different fluidic properties. The obtained results indicate that the carbon dots do not alter the quality of graphene. Atomic force microscopy and Raman spectroscopy are used to study the morphological and structural properties of the carbon dots/graphene nanocomposites supported on SiO2/Si substrate in order to understand if and how the properties of the native materials are modified because of their interaction. The obtained results indicate that the carbon dots do not alter the quality of graphene. [ABSTRACT FROM AUTHOR]

Schottky‐barrier solar cells (SBSCs) represent low‐cost candidates for photovoltaics applications. The engineering of the interface between absorber and front electrode is crucial for reducing the dark current, blocking the majority carriers injected into the electrode, and reducing surface recombination. The presence of tailored interfacial layers between the metal electrode and the semiconductor absorber can improve the cell performance. In this work, the interface of a graphene/n‐type Si SBSC by introducing a graphene‐based derivative (GBD) layer meant to reduce the Schottky‐barrier height (SBH) and ease the charge collection are engineered. The chemical vapor deposition (CVD) parameters are tuned to obtain the two graphene films with different structure and electrical properties: few‐layer graphene (FLG) working as transparent conductive electrode and GBD layer with electron‐blocking and hole‐transporting properties. Test SBSCs are fabricated to evaluate the effect of the introduction of GBD as interlayer into the FLG/n‐Si junction. The GBD layer reduces the recombination at the interface between graphene and n‐Si, and improves the external quantum efficiency (EQE) with optical bias from 50 to 60%. The FLG/GBD/n‐Si cell attains a power conversion efficiency (PCE) of ≈5%, which increase to 6.7% after a doping treatment by nitric acid vapor. A graphene/n‐type‐Si Schottky barrier solar cell with a graphene‐based derivative interlayer are designed and fabricated. This interlayer reduces the Schottky‐barrier height between the Si absorber and the top conductive graphene, limiting the interfacial recombination and increasing the external quantum efficiency of the cell. By a chemical doping treatment, the solar cell achieves a power conversion efficiency of 6.7%. [ABSTRACT FROM AUTHOR]

This work demonstrates that upon anodic polarization in an aqueous fluoride-containing electrolyte, TiO 2 nanotube array films can be formed with a well-defined crystalline phase, rather than an amorphous one. The crystalline phase was obtained avoiding any high temperature annealing. We studied the formation of nanotubes in an HF/H 2 O medium and the development of crystalline grains on the nanotube wall, and we found a facile way to achieve crystalline TiO 2 nanotube arrays through a one-step anodization. The crystallinity of the film was influenced by the synthesis parameters, and the optimization of the electrolyte composition and anodization conditions (applied voltage and time) were carried out. For comparison purposes, crystalline anatase TiO 2 nanotubes were also prepared by thermal treatment of amorphous nanotubes grown in an organic bath (ethylene glycol/NH 4 F/H 2 O). The morphology and the crystallinity of the nanotubes were studied by field emission gun-scanning electron microscopy (FEG-SEM) and Raman spectroscopy, whereas the electrochemical and semiconducting properties were analyzed by means of linear sweep voltammetry, impedance spectroscopy, and Mott-Schottky plots. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) allowed us to determine the surface composition and the electronic structure of the samples and to correlate them with the electrochemical data. The optimal conditions to achieve a crystalline phase with high donor concentration are defined.