A precise evaluation of caries excavation endpoint is essential in clinical and laboratory investigations. Caries invasion differentiates dentin into structurally altered layers. This study assessed these changes using Raman spectroscopy and Vickers microhardness. Ten permanent molars with occlusal and proximal carious lesions were assessed and compared at 130 points utilizing four Raman spectroscopic peaks: phosphate v1 at 960 cm−1, amide I (1650 cm−1), amide III (1235 cm−1) and the C-H bond of the pyrrolidine ring (1450 cm−1). The phosphate-to-amide I peak ratio and collagen integrity peak ratio (amide III: C-H bond) of carious zones were calculated and compared in both lesions. The former ratio was correlated to 130 Vickers microhardness indentations through lesions. The caries-infected dentin (CID) exhibited low phosphate peak, but higher amide I, III and C-H bond peaks than other zones in both lesions. The peaks in amide regions (I and III) varied in occlusal versus proximal lesions. A high correlation was found between mineral: matrix peak ratio and equivalent microhardness number within carious lesions, while the collagen integrity peak ratio was applied in proximal lesions only. Raman spectroscopy detected changes in the mineral and matrix contents within different carious zones and regions.

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CuO thin films on porous silicon (PSi) substrates were prepared via spray pyrolysis method. The structural, optical and electrical properties of the films and the heterojunctions were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-Vis spectrophotometer. XRD results show that the film is polycrystalline and have a monoclinic crystal structure. Optical measurement indicates that the films had a low transmittance at the visible range and an optical bandgap of 2.2[Formula: see text]eV. High rectification was achieved with a maximum photoresponsivity of about 0.59[Formula: see text]A/W at 400[Formula: see text]nm, so that the CuO/PSi heterojunction may act as a good candidate for the fabrication of an efficient photodiode.

Crystalline silicon (c-Si) solar cells have dominated the photovoltaic industry for decades. However, due to high reflectivity and the presence of numerous types of surface contaminants, the solar cell only absorbs a limited amount of the incident solar radiation. To improve the efficiency of the solar cell, anti-reflection and self-cleaning coatings must be applied to the surface. The main objective of this work is to synthesize an amorphous carbon nitride CNx thin film as a novel dual-function anti-reflection coating (ARC) for c-Si solar cells. The CNx film was synthesized by the RF magnetron sputtering technique and characterized by different chemical, structural, and optical analysis techniques. The performance of CNx film was investigated via measuring the reflectance, photoelectric conversion efficiency, and external quantum efficiency. The minimum reflectance was 0.3% at 550 nm wavelength, and the external quantum efficiency achieved was more than 90% within the broad wavelength range. The open circuit voltage and short circuit current density that have been achieved are 578 mV and 33.85 mAcm−2, respectively. Finally, a photoelectric conversion efficiency of 13.05% was achieved with the coated c-Si solar cell in comparison with 5.52% for the uncoated c-Si solar cell. This study shows that CNx films have promising application potential as an efficient ARC for c-Si solar cells as compared to traditional ARC materials.

This study evaluated the structural changes of enamel treated by the Regenerate system and carbon dioxide (CO2) laser against acid challenge. Thirty human enamel slabs were prepared and assigned into three groups: Group I: untreated (control); Group II: treated with the Regenerate system; and Group III exposed to CO2 laser. All specimens were subjected to an acid challenge (pH 4.5–7.0) for 14 days. Specimens were evaluated and compared at 120 points using five Raman microspectroscopic peaks; the phosphate vibrations ν1, ν2, ν3, and ν4 at 960, 433, 1029, and 579 cm−1, respectively, and the carbonate at 1070 cm−1, followed by Vickers microhardness test. The ratio of carbonate to phosphate was correlated to the equivalent microhardness numbers. The intensities of phosphate peaks ν1, ν2, and ν4 were reduced in all groups post-acid challenge, while the carbonate and ν3 were significantly increased (p < 0.000). Surfaces treated by Regenerate exhibited higher peak intensity of phosphate and carbonate before and after pH-cycling (p < 0.05). The mineral content in enamel had a direct effect on tissue microhardness, and the CO2-lased surfaces showed a reduced carbonate content and higher microhardness values. Both approaches induced surface changes that can protect enamel against acid challenge resulting in a significant benefit for dental healthcare.