Fine Nanostructure Research Articles

A ternary-structured NiCo-LDH/Ni/BiVO4 photoanode with enhanced charge dynamics for photoelectrochemical water splitting

Solar-driven photoelectrochemical (PEC) water splitting is one of the promising technologies to produce green hydrogen as the carbon-free energy carrier. However, the ideal photoanode material BiVO4 still suffers from sluggish carrier dynamic problem. Here, NiCo-LDH/Ni/BiVO4 (NC/N/BVO) composite photoanode with a three-layer structure was successfully fabricated by introducing Ni layer followed by NiCo-LDH on BiVO4 by magnetron sputtering and electrochemical deposition, respectively. The optimized structure of NC/N/BVO exhibited a photocurrent of 4.15 mA cm−2 (1.23 VREH) in neutral solution, which was 2.8 times of pristine BiVO4. Besides, the photocurrent can be well maintained at 98 % for NC/N/BVO in 1h reaction, which dramatically decreases to 60 % for BiVO4. In this composite photoanode, NiCo-LDH as excellent water oxidation catalyst can effectively enhance the kinetic process of water oxidation on the surface, while the introduction of Ni layer can not only promote the following deposition of NiCo-LDH being a finer nanostructure with high surface area, but also increase the charge conduction efficiency and promote the charge transfer process between NiCo-LDH and BiVO4 substrate. The appropriate deposition sequence of Ni and NiCo-LDH layers ultimately highly improved the charge injection efficiency of NC/N/BVO resulting in a high performance of PEC water splitting.

Influence of P and C co-alloying on soft magnetic properties and crystallization behavior of FeSiBPCCu nanocrystalline alloys

In this study, multicomponent synergistic effects were adopted to enhance the glass-forming ability (GFA), processing window (PW), thermal stability, and soft magnetic properties (SMPs) of FeCuSiB nanocrystalline alloys (NAs) with high Fe and Cu contents via P and C co-alloying. The co-addition of P and C is beneficial for enhancing the GFA, expanding the PW, and increasing the crystallization resistance of the compound phases in present FeCuSiBPC alloys. Consequently, the Fe81.5Cu1.7Si3.8B9P3C1 alloy exhibited a large optimum TA window of up to 100 °C and a large tA window of 40 min for nanocrystallization. Crystallization kinetic analysis showed that the co-addition of P and C led to a high-frequency factor (v) in the precipitation of α-Fe crystals, which was related to the high nanocrystal density (Nd) of α-Fe. This result may be attributed to the nucleation of α-Fe by Cu and CuP clusters. Additionally, the co-addition of P and C increased the growth active energy (Ep) of the α-Fe crystals because of their larger atomic diffusion resistance. The high Nd and Ep values led to the formation of fine nanostructures and excellent SMPs in FeCuSiBPC alloys. Therefore, the Fe81.5Cu1.7Si3.8B9P3C1 NA obtained by annealing at 420 °C for 30 min exhibited excellent SMPs with a Bs of up to 1.78 T, a low Hc of 7.5 A/m, and a high μe of 9863 (@1kHz). This study provides technical and theoretical guidance for optimizing the composition and processability of NAs with high Fe and Cu contents, paving the way for mass production of high-performance soft magnetic NAs.

Rapid-annealed FeSiBPCu nanocrystalline alloy with high Bs approaching 1.9 T and good bendability

To promote energy savings, high efficiency and miniaturization of power electronic devices, Fe–Si–B–P–Cu nanocrystalline soft magnetic materials with high saturation magnetization (Bs) parallel to that of the 6.5 wt% Si steel and low coercivity (Hc) are desired. In this work, 30 μm-thick Fe84Si3B10P2Cu1 and Fe84.5Si3B9.5P2Cu1 (at.%) amorphous/nanocrystalline precursor ribbons were melt-spun, which has high Fe contents comparable to that of the 6.5 wt% Si steel. These ribbons consist of an amorphous matrix and pre-existing α-Fe of approximately 28–30 nm in size possessed relatively low and similar-value activation energy of nucleation and growth in the range of 224–249 kJ/mol. Which could induce strong crystallization competition and effectively suppress coarsening of the pre-existing α-Fe. The Fe84Si3B10P2Cu1 nanocrystalline alloy obtained by rapid-annealing (∼100 °C/s) the amorphous/nanocrystalline precursor at 480 °C for 30 s (Fe84-480) exhibited a fine and uniform nanostructure containing α-Fe with small average grain size of approximately 23.1 nm and high volume fraction. The Fe84-480 alloy possessed a high Bs of approximately 1.88 T, a low Hc of 8.6 A/m, and good bendability revealed by relatively large bending fracture strain of ∼1.65%, making it a promising soft magnetic material for power electronic devices.

Fabrication of Ag2MoO4/CuWO4 Nanocomposite Photocatalyst for the Degradation of Rhodamine‐B

AbstractHerein, we investigate the photocatalytic properties of a new Ag2MoO4/CuWO4 composite. Three different composites with 5, 10, and 15 weight percent of fine Ag2MoO4 nanostructures were precipitated on CuWO4 nanoparticles. Given the staggered valence and conduction band positions of the two components, the composite with the 10 % weight percent Ag2MoO4 loading on CuWO4 demonstrated the slowest recombination kinetics. The same composite also exhibited the best photocatalytic degradation of RhB under UV light irradiation. The photocatalytic turnover frequency of this composite was also among the best reported for RhB degradation reported in the literature. Photocatalytic kinetics, active species trapping, and various control experiments were carried out to get an insight into the photocatalytic mechanism. The optimum photocatalyst exhibited its highest activity at pH 3 and a RhB degradation turnover frequency (photocatalytic activity) comparable to the best values reported in the literature.

Growth of micro-flowers behind hydrophobic polymer surface and impact of silver and tungsten oxide on the wetting characteristics

In this work, a simple and one-step process was demonstrated to develop hydrophobic polymer surfaces. Commercially available polycarbonate (PC) was treated to turn the front surface hydrophobic with an average wetting contact angle (WCA) as high as 110.5°. The formation of micro-flowers with a coverage density of 9.29 × 106/cm2 on the top of fine base nanostructures was confirmed by a high-resolution field emission scanning electron microscope (FESEM). Impact of typical metal and metal oxide such as silver (Ag) and tungsten oxide (WO3) deposited on such hydrophobic surfaces was demonstrated. Petals of micro-flowers and fine base nanostructures were well decorated with functional metals such as Ag and thus the front surface remained hydrophobic with an average WCA as high as 106.6°. Abundant sharp spikes on the top of narrow hills and dips as revealed in the high-resolution FESEM investigation, were speculated to be the reason behind this hydrophobic characteristic. On the other hand, the hydrophobic surface (WCA of ∼ 110.5°) turned hydrophilic (WCA of ∼11.7°) when the surface was decorated with functional metal oxides, such as WO3. Sessile drop tests were carried out to record average WCA and to understand the wetting characteristics of the specimens. A plausible mechanism for such hydrophobic characteristics as well as the transition from a hydrophobic state to a hydrophilic state has been elucidated.

The Optimization of the One-Pot Synthesis of Au@SiO2Core-Shell Nanostructures: Modification with Dansyl Group and Their Fluorescent Properties.

This work describes the optimization of the one-pot synthesis of fine core-shell nanostructures based on nanogold (Au NPs) and silica (SiO2). The obtained core-shell nanomaterials were characterized by Transmission Electron Microscopy (TEM and by the method of spectroscopes such as UV-Vis Spectroscopy and Fourier Transform Infrared Spectroscopy (FT-IR). In addition, the measurement of the zeta potential and size of the obtained particles helped present a full characterization of Au@SiO2 nanostructures. The results show that the influence of reagents acting as reducers, stabilizers, or precursors of the silica shell affects the morphology of the obtained material. By controlling the effect of the added silica precursor, the thickness of the shell can be manipulated, the reducer has an effect on the shape and variety, and then the stabilizer affects their agglomeration. This work provides also a new approach for Au@SiO2core-shell nanostructure preparation by further modification with dansyl chloride (DNS-Cl). The results show that, by tuning the silica shell thickness, the intensity of the fluorescence spectrum of Au@SiO2-(CH2)3-NH-DNS nanocomposite is about 12 times higher than that of DNS-Cl.

Effects of Si addition on crystallization process and soft magnetic properties of high-Fe and high-Cu-content Fe–Si–B–P–Cu nanocrystalline alloys

In this study, the effects of Si content on the glass-forming ability (GFA), thermal stability, annealing window, nanocrystallization process, and soft magnetic properties (SMPs) of Fe86.3-xSixB10P2Cu1.7 (x = 0, 1, 2, 3, and 4, denoted as Si0, Si1, Si2, Si3, and Si4, respectively) alloys with high Fe and Cu contents were investigated. Moderate addition of Si (x = 1, 2, and 3) enhanced the GFA and suppressed the precipitation of compound phases, thus leading to a large crystallization temperature interval (ΔTx) exceeding 185 °C for the alloys. Appropriate addition of Si also resulted in the formation of high-density and fine pre-existing α-Fe nanocrystals in as-spun ribbons and a high growth active energy of α-Fe crystals during the subsequent nanocrystallization process for the Si1, Si2, and Si3 alloys, enhancing competitive growth between α-Fe crystals and resulting in fine nanostructure and excellent SMPs of the nanocrystalline alloys (NAs). As a result, the Si1, Si2, and Si3 NAs obtained by annealing at 420 °C for 30 min exhibited excellent SMPs with saturation magnetic flux density (Bs) up to 1.84 T and a low coercivity (Hc) of approximately 10 A/m. In addition, statistical analysis of the relationship between the average grain size (D) of α-Fe crystals and Hc values of the NAs indicated that an Hc α D3 dependence is observed when the D is less than approximately 30 nm, while this dependence follows the well-known Hc α D6 relationship when the D is above 30 nm. The dependency relationship between D and Hc of NAs can guide the selection of an appropriate annealing process to optimize their SMPs.

Effects of Cr addition on structure, magnetic properties and corrosion resistance of a Fe85.5B13Cu1.5 nanocrystalline alloy

The melt-spun structure of a Fe85.5B13Cu1.5 alloy was regulated by the addition of corrosion-resistant Cr with a moderate enhancement in amorphous-forming ability, which further refines the nanostructure and improves the soft magnetic properties and corrosion resistance of corresponding nanocrystalline alloys. The results show that high-number-density α-Fe grains in size of below 10 nm are formed in the amorphous matrix of melt-spun Fe85.5-xB13Cu1.5Crx (x = 0–6) alloy ribbons, and the grain size and number density gradually decrease with the increase in Cr content. After annealing, the α-Fe average grain size (Dα-Fe) and coercivity (Hc) of corresponding nanocrystalline alloys reduce significantly with increasing x from 0 to 3, and the reduction becomes less pronounced within x = 3–6, while the saturation magnetic flux densities (Bs) steadily decreases as x increases from 0 to 6. A Fe82.5B13Cu1.5Cr3 nanocrystalline alloy with the Dα-Fe of 14.9 nm possesses excellent comprehensive soft magnetic properties with the Hc and Bs of 13.8 A/m and 1.74 T, respectively. The fine nanostructure and good magnetic softness results from the optimum combination of pre-existing α-Fe competitive growth and Cr-inhibited atom diffusion. The nanocrystalline alloys show improved corrosion resistance in NaCl solution compared to their respective melt-spun precursors, and the addition of Cr further enhances the corrosion resistance. The alloyed Cr also reduces the annealing embrittlement of the nanocrystalline alloys.

Optimization of Surface Roughness of Aluminium RSA 443 in Diamond Tool Turning

Context—Rapidly solidified aluminium alloy (RSA 443) is increasingly used in the manufacturing of optical mold inserts because of its fine nanostructure, relatively low cost, excellent thermal properties, and high hardness. However, RSA 443 is challenging for single-point diamond machining because the high silicon content mitigates against good surface finishes. Objectives—The objectives were to investigate multiple different ways to optimize the process parameters for optimal surface roughness on diamond-turned aluminium alloy RSA 443. The response surface equation was used as input to three different artificial intelligence tools, namely genetic algorithm (GA), particle swarm optimization (PSO), and differential evolution (DE), which were then compared. Results—The surface roughness machinability of RSA443 in single-point diamond turning was primarily determined by cutting speed, and secondly, cutting feed rate, with cutting depth being less important. The optimal conditions for the best surface finish Ra = 14.02 nm were found to be at the maximum rotational speed of 3000 rpm, cutting feed rate of 4.84 mm/min, and depth of cut of 14.52 µm with optimizing error of 3.2%. Regarding optimization techniques, the genetic algorithm performed best, then differential evolution, and finally particle swarm optimization. Originality—The study determines optimal diamond machining parameters for RSA 443, and identifies the superiority of GA above PSO and DE as optimization methods. The principles have the potential to be applied to other materials (e.g., in the RSA family) and machining processes (e.g., turning, milling).

Porous MCM‐41 Silica Materials as Scaffolds for Silicon‐based Lithium‐ion Battery Anodes

AbstractAiming for specific energy improvements, lithium‐ion battery (LIB) research explores Si based materials as potential alternatives for the negative electrode/anode. Si exhibits a high specific capacity when lithiated, accompanied by a large volumetric expansion. To mitigate expansion induced failures, composite materials with finely distributed Si inside a scaffold have been established. Potential scaffolds to create such Si composites are nano porous SiO2 materials, such as MCM‐41. MCM‐41 exhibits a fine nanostructure, and the synthesis allows precise tuning of the pore properties and thus, after filling with Si, of Si morphology and Si content in the composite. In this work, insights into relevant MCM‐41 synthesis parameters are acquired, with special attention towards specific pore volumes and pore sizes of the SiO2 powders. Materials characterization is performed using nitrogen sorption analysis, X‐ray scattering, electron microscopy and thermogravimetric analysis. Selected MCM‐41 scaffolds are processed to Si composites and integrated into LIB electrodes. The specific capacity and the stability of the Si−SiO2 composites are evaluated by PITT and galvanostatic cycling. They show capacities above 800 mAh g−1, i. e. more than twice the specific capacity of industry standard graphite, and last over 200 charge/discharge cycles before their capacity loss exceeds 25 %.

N-CoFeP/NF electrocatalyst for coupling hydrogen production and oxidation reaction of various alcohols

Replacing the oxygen evolution reaction with the alcohols oxidation reaction (AOR) in electrolytic water is not only expected to reduce the overall energy consumption, but also realize the green synthesis of high value-added chemicals. However, designing high-activity electrocatalysts toward AOR yet faces a daunting challenge due to the indefinite conversion mechanism of different alcohols. Herein, a self-supported N-CoFeP/NF electrocatalyst on a nickel foam is synthesized via hydrothermal method, followed by low temperature nitriding and phosphating. The N-CoFeP/NF exhibits a fine nanorod nanostructure and high crystallinity. The AOR using N-CoFeP/NF catalysts requires a significantly lower potential (1.38–1.42 V vs. RHE) at 100 mA cm−2, reducing the energy input and the improvement of the overall efficiency. Moreover, alcohols with secondary hydroxyl groups located in the middle of the carbon chain underwent CC bond breakage during oxidation, yielding primarily formic acid (FE = 74 %) and acetic acid (FE = 50 %), which exhibits more attractive performance than alcohols with primary hydroxyl groups located at the end group did not undergo chemical bond breakage at a high current density of 400 mA cm−2. This study provides a novel and effective method to design TMPs and the selection of alcohols for anodic reaction, which can be used as a versatile strategy to improve the performance of anodic AOR coupled hydrogen evolution.

Visible light photo-Fenton degradation of p-nitrophenol on Ag/Fe3O4/WO3 nanocomposites: Experimental and molecular dynamics investigations

The present research combines the adsorption behavior of phases in an aqueous medium with their band gap information for constructing a composite photo-Fenton catalyst that degrades para-nitrophenol (PNP). Thus, a series of Ag/ Fe3O4/WO3 Z-scheme photocatalysts were investigated for photo-Fenton PNP degradation. Classical MD simulations predicted effective H2O2 interaction with the photocatalyst's reduction (Fe3O4) part. The decoration of the composite surface by fine Ag nanostructures enhanced the visible light absorption efficiency of the photocatalyst through the localized surface plasmon resonance phenomenon. Photo-Fenton activities of Fe3O4/WO3 composites changed with their Ag loading. The composite with five-weight percent Ag loading demonstrated the best PNP degradation activity. The photoexcitation of Ag/Fe3O4/WO3 photocatalyst results in the accumulation of electrons on the CB of Fe3O4 and holes on the VB of WO3. The H2O2 molecules adsorb on the Fe3O4 part and are reductively cleaved to produce hydroxyl radicals, oxidizing PNP molecules nearby.

Fine periodic nanostructure formation on stainless steel and gallium arsenide with few-cycle 7-fs laser pulses

We report the fine periodic nanostructure formation process on metal and semiconductor surfaces in air with few-cycle 7-fs laser pulses and its physical mechanism. Using appropriate peak power densities and scanning speeds for the laser pulses, nanostructures could be formed on stainless steel and gallium arsenide (GaAs) with periods of 60–110 nm and 130–165 nm, respectively, which are 1/5–1/4 of the period of nanostructures formed with 100-fs laser pulses. The periodicity can be explained as arising from the excitation of short-range propagating surface plasmon polaritons, and the observed periods are in good agreement with the model calculation results.

Solvent-free direct salt precursor mechanochemical synthesis of La0.5Sr0.5Ti0.5Mn0.5O3-δ oxide perovskite and its electrocatalytic behavior as oxygen electrode for solid oxide cells

In this work, a solvent-free mechanochemical route is proposed as a direct salt precursor solid state synthesis for the mixed ionic-electronic conducting (MIEC) Lanthanum Strontium Titanium Manganese oxide perovskite (La0.5Sr0.5Ti0.5Mn0.5O3-δ, LSTM). The resulting mechanochemically synthesized powder is structurally and morphologically characterized and is comprised of fine spherical nanostructures in the sub-micron scale (≤100 nm), with low polydispersity and homogeneous morphology, while the obtained perovskite structure is pure single-phase without any precursor residuals or metal oxide phases. For comparison, conventional synthetic routes (sol-gel and precursor calcination) are presented which result in inferior samples of mixed metal oxides and micron-sized particles. Symmetrical solid oxide cells with single-phase LSTM and LSTM-YSZ composite electrodes reveal a mixed conduction behavior in the temperature range of 700–850 °C under flowing synthetic air atmosphere. With a developed current density of 172 mA cm−2 at 850 °C and +2 V overpotential, and an electrode polarization resistance of 7.5 Ω cm2, perovskite LSTM synthesized by the presented solvent-free direct salt precursor mechanochemical synthesis is therefore proposed as a potential candidate for MIEC electrodes in symmetrical reversible solid oxide cells (r-SOCs).

Polybenzodiazine Aerogels: All-Nitrogen Analogues of Polybenzoxazines─Synthesis, Characterization, and High-Yield Conversion to Nanoporous Carbons

Tetrahydroquinazoline (THQ) was designed as an all-nitrogen analogue of main-stream benzoxazine monomers. THQ solutions in DMF gelled at 100 °C via HCl-catalyzed ring-opening polymerization to polybenzodiazine (PBDAZ) wet gels, which were dried in an autoclave with supercritical fluid CO2 to aerogels. These as-prepared PBDAZ-100 aerogels undergo ring-fusion aromatization at 240 °C under O2. This oxidized form is referred to as PBDAZ-240. Chemical identification of PBDAZ-100 and PBDAZ-240 relied on consideration of all nine possible polymerization pathways, in combination with elemental analysis, infrared and solid-state 13C NMR spectroscopy, and 15N NMR spectroscopy of aerogels from the selectively 15N-enriched THQ monomer. Fully oxidized PBDAZ-240 aerogels were carbonized at 800 °C under Ar to carbon aerogels with 61% w/w yield and with retention of the nanomorphology of the parent PBDAZ-100 aerogels. Direct pyrolysis of PBDAZ-100 at 800 °C, i.e., without prior oxidation, resulted in only 40% w/w yield and complete loss of the fine nanostructure. The evolution of PBDAZ-240 aerogels along pyrolysis toward carbonization was monitored using progressively higher pyrolysis temperatures from 300 to 800 °C under Ar. Aerogels received at 600 and 800 °C (referred to as PBDAZ-600 and PBDAZ-800, respectively) had relatively high surface areas (432 and 346 m2 g–1, respectively), a significant portion of which (79% in both materials) was assigned to micropores. The new polymer aerogels, together with polybenzoxazine aerogels, comprise a suitable basis set for comparing N-rich versus O-rich porous carbons as adsorbers.

Metal-Catalyzed Nanostructured Silicon Films as Potential Anodes for Flexible Rechargeable Batteries

Nanostructured Si is touted to be an inexpensive, safe, and high-capacity anode for advanced thin-film batteries. However, the synthesis of crystalline Si generally requires high temperatures, which limits the choice of substrates. In this study, we synthesized nanostructured Si layers at low temperatures by combining metal-catalyzed crystal growth and etching. The lower crystallinity and finer nanostructures in Si improved the anode characteristics of Li-ion batteries. The capacity of the Si anode reached approximately 3200 mAh g–1 at 0.1 C and 2000 mAh g–1 at 1 C. Further, the low process temperature enabled the fabrication of a Si layer of the same quality on a flexible plastic substrate while maintaining the flexibility. This low-temperature synthesis of nanostructured Si anodes is therefore expected to pioneer the next generation of human-friendly flexible rechargeable batteries.

Microstructure and mechanical properties of zirconia stabilized with increasing Y2O3, for use in dental restorations

AbstractThe present in vitro study aims at characterizing dental zirconia ceramics, which are stabilized with a high amount of Y2O3. Two groups of specimens were fabricated by computer‐aided design/computer‐aided manufacturing technique. The specimens of each group were divided into two subgroups (SGs): SGs 1a and 2a contained a relatively low amount of Y2O3 (6–8 wt.%), whereas SGs 1b and 2b contained a higher amount of Y2O3 (8–10 wt.%). The influence of yttria content on their microstructure and mechanical properties was experimentally determined. The statistical significance of the differences in the mechanical properties between the SGs was evaluated by the t‐test (p < 5% was considered statistically significant). Homogeneous and dense ceramics with fine nanostructure, comprising grains of yttria‐stabilized tetragonal and cubic zirconia, sized between ∼160 and ∼800 nm, were produced. The increase of yttria content, which causes an increase in grain size, favors the formation of cubic zirconia, resulting in mechanical properties’ slight reduction; yet, the differences were not statistically significant. Consequently, the mechanical properties (HV 11.74–12.91 GPa, and KIC 2.66–4.25 MPa m0.5) and the good esthetics of the investigated zirconia ceramics stabilized with high yttria content qualify these zirconia materials for fabricating dental restorations, because they can approach the properties and the esthetics of dental hard tissues as well as the tooth structure.

Transparent Polyimide Aerogels: Controlled Porosity via Minimizing the Phase Separation

The aerogels industry has been growing with a market capacity of 909 billion USD in 2019. Silica aerogels are the most extensively used due to their ease of synthesis. It can possess many useful properties such as high optical transparency, high-surface area, low thermal conductivity, and a wide accessible density range. However, silica aerogels are brittle and friable, making them unsuitable for many applications. Polymeric aerogels are typically much more robust but lack the uniform fine nanostructure which gives silica its exceptional properties. Herein, mechanically robust polyimide (PI) aerogels with uniform <20 nm porosity and exceptional transparency are demonstrated. Optimization was achieved by minimizing the phase separation during gelation, minimizing the light scattering, and yielding the exceptionally transparent aerogels. The aromatic PI backbone results in a high modulus while retaining a low thermal conductivities and high thermal stability. We demonstrate methods for inducing phase separation to increase the pore size and the effects on bulk properties. This study presents a better understanding of the route to producing transparent polymer aerogels.

Phase selection of BCC/B2 phases for the improvement of tensile behaviors in FeNiCrAl medium entropy alloy

With excellent compressive mechanical properties, FeNiCrAl medium entropy alloys with multi-principal components have attracted extensive attention in recent years. However, the limited tensile ductility of FeNiCrAl medium entropy alloys is the bottleneck for their industrial applications. In this work, dual phases of FCC + B2 and BCC + B2 were modulated in FeNiCrAl medium entropy alloys for excellent tensile behaviors. In the as-cast state, the tensile yield strength and ultimate tensile strength are 1140 MPa and 1423 MPa, respectively, with a uniform elongation of 6.0%. • As-cast dual phases FeNiCrAl medium entropy alloys are designed for excellent tensile behavior. • Dual phases of FCC+B2 and BCC+B2 are modulated by changing the valence electron concentration via the ratio of Fe/Ni. • Fe 47 Ni 26 Cr 10 Al 17 alloy has a fine nanostructure with BCC+B2 dual phases. • As-cast Fe 47 Ni 26 Cr 10 Al 17 alloy shows yield strength of 1140 MPa and uniform elongation of 6.0%.

Human Enamel Fluorination Enhancement by Photodynamic Laser Treatment.

Poor oral hygiene leads to serious damages of theteeth’s surface enamel such as micro-abrasions and acid erosion. These alterations combined with bacterial plaque result in cavity appearance. Prophylactic measures include various techniques for enamel surface restoration. Fluorination is one of the most important treatments for this purpose. Therefore, in the present research, we investigated the classical fluorination treatment compared with laser photodynamic fluorination performed on human enamel samples with poor surface quality. Three sample groups were investigated: veneer (F), inlay (I), and crowns (C). The general morphologic aspect was investigated by scanning electron microscopy (SEM), and the specific details such as the fine microstructure and nanostructure were investigated by atomic force microscopy (AFM) of the surface roughness. The samples were also investigated by Fourier transformed infrared attenuated total reflectance (FTIR-ATR) to evidence the fluorination effect on the enamel surface. Results showed that all initial samples had an altered state with micro-abrasions and erosion with mineral loss, which increase the surface roughness. The F group was the most damaged, having a higher roughness, and the I group was less damaged. Classic fluorination treatment partially restored the enamel by local re-mineralization, but did not obtain the parameters of healthy enamel. However, a significant decrease of the roughness was observed (statistical relevance p = 0.001 with the Breusch–Pagan Test). This fact was supported by the presence of newly formed fluorides in the FTIR-ATR spectra. The photodynamic laser fluorination restores the enamel in an enhanced manner by a strong re-mineralization, which implies a significant roughness value decrease comparable to healthy enamel. The Breusch–Pagan Test confirmed the relevance with p = 0.001. This is due to an extended re-mineralization abundant in fluoride crystals as observed by AFM and FTIR. Statistical p-values regarding laser application were in the range of 0.02–0.06, supporting its relevance in the fluorination effect. The final conclusion is that the photodynamic effect is able to favor the newly formed fluoride deposition onto the affected sites of the enamel surface.