Quo Vadis Nonlinear Optics? An Alternative and Simple Approach to Third Rank Tensors in Semiconductors

It is well understood that nonlinear optical (NLO) phenomena are deeply related to the material’s symmetry. Mathematically, the material symmetry can be described in terms of the nonzero parameters in the nonlinear susceptibility tensors. Generally, more complex structures involve more nonzero parameters in the tensor. The number of parameters increases rapidly if higher NLO orders are considered, complicating the physical analysis. Conventionally, these parameters are obtained via abstract symmetry analysis, e.g., group theory (GT). This work presents a novel theoretical analysis to approach the nonlinear tensor using the simplified bond hyperpolarizability model (SBHM) and compare it with GT. Our analysis is based on a light–matter interaction classical phenomenological physical framework. Rather than just looking at the symmetry of the crystal, the model applies physical considerations requiring fewer independent parameters in the tensor than GT. Such a simplification significantly improves the determination of the surface–bulk SHG contribution factors, which cannot be extracted from the experiment alone. We also show for the case of perovskite that the SHG contribution can be addressed solely from their surface dipoles with only one independent component in the tensor. Therefore, this work may open the path for a similar analysis in other complicated semiconductor surfaces and structures in the future, with potential applications to nanoscale surface characterization and real-time surface deposition monitoring.

Poly (ε-caprolactone)/Poly (lactic acid) fibers produced by rotary jet spinning for skin dressing with antimicrobial activity

The rotary jet spinning technique permits the production of biomaterials that can be used as devices that come into contact with biological systems (including biological fluids) for diagnostic or surgical applications. These materials are composed of synthetic or natural compounds and allow the incorporation of drugs for therapeutic purposes. Two solutions containing 50% poly(lactic acid) (PLA) and 50% poly(ε-caprolactone) (PCL) diluted in three different solvents were prepared for rotary jet spinning (RJS) process. Vancomycin, an antibiotic indicated for the treatment of severe staphylococcal infections in patients with penicillin allergy, was added in the polymer solutions, to obtain drug-loaded fibrous mats. Morphological surface characterization by scanning electron microscopy revealed heterogeneous pores in the microfibers. Vancomycin loading interfered with the morphology of all samples in terms of fiber size, leading to smaller diameter fibers. Attenuated total reflectance/Fourier transform infrared spectroscopy was used for identification of the samples. The vibrational characteristics of PCL/PLA and vancomycin were consistent with expectations. Vero cell culture assays by the extract dilution and direct contact methods revealed the absence of cytotoxicity, except for the sample prepared with 50% of PCL and of a 9/2 (V/V) vancomycin content, with the growth of confluent and evenly spread cells on the fibrous mats surface. Microbiological analysis, performed on Staphylococcus aureus by the halo inhibition test and by the broth dilution method, showed that the antibacterial activity of vancomycin was maintained by the loading process in the polymer fibers. The results showed that rotary jet spinning produces satisfactory amounts of Vancomycin-loaded fibers, as potential web dressing for wound repair

Amine Plasma-Polymerization of 3D Polycaprolactone/β-Tricalcium Phosphate Scaffold to Improving Osteogenic Differentiation In Vitro

This study aims to investigate the surface characterization and pre-osteoblast biological behaviors on the three-dimensional (3D) poly(ε-caprolactone)/β-tricalcium phosphate (β-TCP) scaffold modified by amine plasma-polymerization. The 3D PCL scaffolds were fabricated using fused deposition modeling (FDM) 3D printing. To improve the pre-osteoblast bioactivity, the 3D PCL scaffold was modified by adding β-TCP nanoparticles, and then scaffold surfaces were modified by amine plasma-polymerization using monomer allylamine (AA) and 1,2-diaminocyclohexane (DACH). After the plasma-polymerization of PCL/β-TCP, surface characterizations such as contact angle, AFM, XRD, and FTIR were evaluated. In addition, mechanical strength was measured by UTM. The pre-osteoblast bioactivities were evaluated by focal adhesion and cell proliferation. Osteogenic differentiation was investigated by ALP activity, Alizarin red staining, and Western blot. Plasma-polymerization induced the increase in hydrophilicity of the surface of the 3D PCL/β-TCP scaffold due to the deposition of amine polymeric thin film on the scaffold surface. Focal adhesion and proliferation of pre-osteoblast improved, and osteogenic differentiation was increased. These results indicated that 3D PCL/β-TCP scaffolds treated with DACH plasma-polymerization showed the highest bioactivity compared to the other samples. We suggest that 3D PCL/β-TCP scaffolds treated with DACH and AA plasma-polymerization can be used as a promising candidate for osteoblast differentiation of pre-osteoblast.

The Influence of Storage in Saline or Irradiation by Ultraviolet on Implant Hydrophilicity and Osseointegration: An Experimental Study in Rabbits

Storage in aqueous solution or ultraviolet (UV) irradiation can re t ain or regain the hydrophilicity of titanium implant surface. In this study, t hree types of commercial titanium implants were used : ZBL (ZDI Bone L evel ® ), CEL (C-tech Esthetic Line ® ) , and modSLA (Straumann SLActive ® ). ZBL and CEL implants were treated with UV irradiation for 4 h. Surface characterization of the four groups (ZBL, ZBL-UV, CEL-UV, modSLA) was evaluated by scanning electron microscopy and contact angle measurements. The in vivo bone response was evaluated by removal torque (RTQ) tests and histomorphometric analysis at 3, 6 , and 12 weeks post-implantation. A total of 144 implants and 36 rabbits were used for experiments according to a previously established randomization sequence. The ZBL-UV, CEL-UV , andmodSLA groups were hydrophilic, and nanostructures were observed on the modSLA implant surface.ModSLA achieved better RTQ value than ZBL at 12 weeks ( p <0.05). For histomorphometric analysis, ZBL-UV and CEL-UV implants showed higher bone area values in the cancellous bone zone at 6 weeks than did modSLA and ZBL implants ( p <0.05).In the cortical bone zone, all groups showed comparable bone-to-implant contact at all healing time points ( p >0.05).Both storage in saline and UV irradiation could retain or provoke hydr o philic surfaces and improve osseointegration. Compared to storage in saline, UV irradiation displayed slight advantages in promoting new bone formation in cancellous bone zone at an early stage.

Amphiphilic Zirconium Phosphate Nanoparticles as Tribo-catalytic Additives of Multi-performance Lubricants

The advancement of electric vehicles demands lubricants with multifunction and performance. In this research, we investigated amphiphilic a-ZrP nanoparticles as lubricant additives. Experimetns showed that the nanolubricant produced a tribofilm reduced the friction for 40% and wear 90%, while the electrical conductivity remained to be stable during tribotesting. Surface characterization of the tribofilm showed that there was a layered pyrophosphate on the wear track . The in situ impedance study about tribochemical kinetics revealed that the process in formation of a tribofilm involved synergetic growth and wear. During growth, the coefficient of friction increased with continued formation of such a file. During wear, the material removal rate was a function of friction, i.e., the higher the wear rate, the higher the friction coefficient. The competing mechanisms of film growth and wear resulted in an electrically uniformed surface.

Novel CNT Supported Molybdenum Catalyst for Detection of L-Cysteine in Its Natural Environment

In this study, novel carbon nanotube-supported Mo (Mo/CNT) catalysts were prepared with the sodium borohydride reduction method for the detection of L-cysteine (L-Cys, L-C). Mo/CNT catalysts were characterized with scanning electron microscopy with elemental dispersion X-ray (EDX-SEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectrometry (UV-vis), temperature-programmed reduction (TPR), temperature programmed oxidation (TPO), and temperature-programmed desorption (TPD) techniques. The results of these advanced surface characterization techniques revealed that the catalysts were prepared successfully. Electrochemical measurements were employed to construct a voltammetric L-C sensor based on Mo/CNT catalyst by voltammetric techniques such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Further measurements were carried out with electrochemical impedance spectroscopy (EIS). Mo/CNT/GCE exhibited excellent performance for L-C detection with a linear response in the range of 0–150 µM, with a current sensitivity of 200 mA/μM cm2 (0.0142 μA/μM), the lowest detection limit of 0.25 μM, and signal-to-noise ratio (S/N = 3). Interference studies showed that the Mo/CNT/GCE electrode was not affected by D-glucose, uric acid, L-tyrosine, and L-trytophane, commonly interfering organic structures. Natural sample analysis was also accomplished with acetyl L-C. Mo/CNT catalyst is a promising material as a sensor for L-C detection.