Skin is the largest organ and a multifunctional interface between the body and its environment. It acts as a barrier against cold, heat, injuries, infections, chemicals, radiations or other exogeneous factors, and it is also known as the mirror of the soul. The skin is involved in body temperature regulation by the storage of fat and water. It is an interesting tissue in regard to the local and transdermal application of active ingredients for prevention or treatment of pathological conditions. Topical and transdermal delivery is an emerging route of drug and cosmetic administration. It is beneficial for avoiding side effects and rapid metabolism. Many pharmaceutical, technological and cosmetic innovations have been described and patented recently in the field. In this review, the main features of skin morphology and physiology are presented and are being followed by the description of classical and novel nanoparticulate dermal and transdermal drug formulations. The biophysical aspects of the penetration of drugs and cosmetics into or across the dermal barrier and their investigation in diffusion chambers, skin-on-a-chip devices, high-throughput measuring systems or with advanced analytical techniques are also shown. The current knowledge about mathematical modeling of skin penetration and the future perspectives are briefly discussed in the end, all also involving nanoparticulated systems.

Confocal Raman Spectroscopy is recognised as a potent tool for molecular characterisation of biological specimens. There is a growing demand for In Vitro Permeation Tests (IVPT) in the pharmaceutical and cosmetic areas, increasingly conducted using Reconstructed Human Epidermis (RHE) skin models. In this study, chemical fixation of RHE in 10 % Neutral Buffered Formalin for 24 h has been examined for storing RHE samples at 4 °C for up to 21 days. Confocal Raman Spectroscopy (CRS), combined with Principal Components Analysis, revealed the molecular-level effects of fixation, notably in protein and lipid conformation within the stratum corneum and viable epidermis. IVPT by means of high-performance liquid chromatography, using caffeine as a model compound, showed minimal impact of formalin fixation on the cumulative amount, flux, and permeability coefficient after 12 h. While the biochemical architecture is altered, the function of the model as a barrier to maintain rate-limiting diffusion of active molecules within skin layers remains intact. This study opens avenues for enhanced flexibility and utility in skin model research, promising insights into mitigating the limited shelf life of RHE models by preserving performance in fixed samples for up to 21 days.

A facile solid-state approach is employed to synthesize a novel magnetoplumbite-type oxide of NdMgAl11O19, which integrates spinel-stacking layers (MgAl2O4) with Nd-O6 mirror plane structures. The resulting NdMgAl11O19 exhibits remarkable catalytic activity and conversion efficiency during the sulfur reduction reaction (SRR) in lithium-sulfur batteries. By employing the 2D projection mapping technique of in situ confocal Raman spectroscopy and electrochemical technique, it is discovered that the exposed mirror plane structure of Nd-O6 can effectively suppress the undesiring disproportionation reaction (S8 2-→S6 2-+1/4 S8) of long-chain lithium polysulfides at the initial stages of sulfur reduction, thereby promoting the positive process of sulfur to lithium sulfide. This not only mitigates the issue of sulfur shuttle loss but also significantly improve the kinetics of the conversion process. Leveraging these advantages, the NdMgAl11O19/S cathode delivered an impressive initial capacity of up to 1398 mAh g-1 at an electrolyte/sulfur (E/S) ratio of 5.1 µL mg-1 and a sulfur loading of 2.3 mg cm-2. Even when the sulfur loading is increased to 10.02 mg cm-2, the cathode retained a reversible areal capacity of 10.01 mAh cm-2 after 200 cycles. This mirror engineering strategy provides valuable and universal insights into enhancing the efficiency of cathodes in Li-S battery.

Large-area two-dimensional (2D) materials possess significant potential in the development of next generation semiconductor due to their unique physicochemical properties. Confocal Raman spectroscopy (CRM), a typical 2D material characterization method, has a limited effective measurement area owing to the restricted focus depth of the system and the less-than-ideal level of the substrate. We propose fast adaptive focusing confocal Raman microscopy (FAFCRM) to realize real-time focusing detection for large-area 2D materials. By observing spot changes on the charge coupled device (CCD) caused by placing an aperture in front of the CCD, the methodology gives a focusing resolution up to 100 nm per 60 μm without axial scanning. A graphene was measured over 25.6 mm × 25.6 mm area on focus through all the scanning. The research results provide new perspectives for non-destructive characterization of 2D materials at the inch level.

MoS2 is a two-dimensional layered transition metal dichalcogenide with unique electronic and optical properties. The fabrication of ultrathin MoS2 is vitally important, since interlayer interactions in its ultrathin varieties will become thickness-dependent, providing thickness-governed tunability and diverse applications of those properties. Unlike with a number of studies that have reported detailed information on direct bandgap emission from MoS2 monolayers, reliable experimental evidence for thickness-induced evolution or transformation of the indirect bandgap remains scarce. Here, the sulfurization of MoO3 thin films with nominal thicknesses of 30 nm, 5 nm and 3 nm was performed. All sulfurized samples were examined at room temperature with spectroscopic ellipsometry and photoluminescence spectroscopy to obtain information about their dielectric function and edge emission spectra. This investigation unveiled an indirect-to-indirect crossover between the transitions, associated with two different Λ and K valleys of the MoS2 conduction band, by thinning its thickness down to a few layers.

As performance of ternary amorphous solid dispersions (ASDs) depends on the solid-state characteristics and polymer mixing, a comprehensive understanding of synergistic interactions between the polymers in regard of dissolution enhancement of poorly soluble drugs and subsequent supersaturation stabilization is necessary. By choosing hot-melt extrusion (HME) and vacuum compression molding (VCM) as preparation techniques, we manipulated the phase behavior of ternary efavirenz (EFV) ASDs, comprising of either hydroxypropyl cellulose (HPC)-SSL or HPC-UL in combination with Eudragit® L 100-55 (EL 100-55) (50:50 polymer ratio), leading to single-phased (HME) and heterogeneous ASDs (VCM). Due to higher kinetic solid-state solubility of EFV in HPC polymers compared to EL 100-55, we visualized higher drug distribution into HPC-rich phases of the phase-separated ternary VCM ASDs via confocal Raman microscopy. Additionally, we observed differences in the extent of phase-separation in dependence on the selected HPC grade. As HPC-UL exhibited decisive lower melt viscosity than HPC-SSL, formation of partially miscible phases between HPC-UL and EL 100-55 was facilitated. Consequently, as homogeneously mixed polymer phases were required for optimal extent of solubility improvement, the manufacturing-dependent differences in dissolution performances were smaller using HPC-UL, instead of HPC-SSL, i.e. using HPC-UL was less demanding on shear stress provided by the process.

Although numerous experiments on benzophenone-3 (BP3) have shown that it can permeate into the skin, the in vivo penetration situation and urinary metabolic trend have not yet been investigated. In this study, sunscreen containing 5.72% BP3 was selected for human-skin exposure. Confocal Raman was successfully used to investigate in vivo skin penetration of BP3 in sunscreen. During 2 h of skin exposure, the semi-quantitative mean values were 5.50, 13.48, 15.79, and 15.00 μg/cm2 after application of sunscreen for 15, 30, 60, and 120 min, respectively, indicating that BP3 penetrated the stratum corneum during 60-120 min. After a single exposure of human limbs, BP3 was quickly metabolized and excreted through urine and reached its peak concentration in the 6th hour, whereas its metabolite 2,4-dihydroxybenzophenone (BP1) reached its peak concentration in the 9th hour. Meanwhile, 6% BP3 and 1% BP1 were excreted through the urine within 48 h, but the concentration of 2,2\'-dihydroxy-4-methoxybenzophenone (BP8) was low, although it varied greatly within 48 h after exposure. During consecutive exposures, a significant correlation (p < 0.05) between BP3 concentration and exposure time was found, indicating that BP3 concentration increased at longer exposure times. Therefore, combining Raman spectroscopy and human sample analysis provided a new way to assess absorption and metabolism of personal care additives in the human body.

Blueberry anthocyanin (BA) is a functional ingredient to enhance the biological activity of food, and the stability of BA is of great interest. BA stability in aqueous solutions stored in polypropylene and glass bottles was analyzed in-situ using confocal Raman spectroscopy, and the acceptable depth of focus was optimized. The Raman characteristics of BA degradation were explained by multivariate analysis. The degradation rate of BA was significantly accelerated by heating above 65 °C for 2 h or ultraviolet irradiation (10 W) for 96 h. The first order kinetic reaction rate was accelerated with the increase of pH value and temperature and the prolongation of ultraviolet irradiation time. The synergistic effect of multiple factors promoted BA degradation. This study provides an in-situ, nondestructive method for the analysis of anthocyanin stability, which has great utility in the food industry to optimize processing, storage, and transportation measures to reduce the degradation of BA.

Si is known for cracking and delamination during electrochemical cycling of a battery due to the large volume change associated with Li insertion and extraction. However, it has been found experimentally that patterned Si island electrodes that are 200 nm thick and less than 7 μm wide can deform in a purely elastic manner. Inspired by this, we performed in situ Raman stress characterization of model poly-crystalline Si island electrodes using an electrochemical cell coupled with an immersion objective lens and designed for a short working distance. A 5 μm wide Si island electrode showed a parabolic stress profile during lithiation, while for a 15 μm Si island electrode, a stress plateau in the center of the electrode was observed. A continuum model with coupled electro-chemo-mechanical (ECM) physics was established to understand the stress measurement. A qualitative agreement was reached between modeling and experimental data, and the critical size effect could be explained by the Li diffusive flux as governed by competition between the Li concentration and hydrostatic stress gradients. Below the critical size, the stress gradient drives Li toward the edges, where the electrode volume is free to expand, while above the critical size, the stress plateau inhibits Li diffusion to the edge and forces destructive stress relief by cracking. This work represents a promising methodology for in situ characterization of ECM coupling in battery electrodes, with suggestions provided for further improvement.

A handheld non-invasive confocal Raman system (CRS) was used to evaluate the differences in skin biochemicals between atopic dermatitis (AD) and psoriasis, which are inflammatory skin conditions. Raman spectral measurements in the fingerprint and high wavenumber region were acquired using a portable in-house CRS system with excitation lasers operating at 671 and 785 nm. It was deduced that relative amount of water decreases in the following sequence of skin: healthy, psoriasis and AD. Moreover, differential trends were observed for the subclasses of ceramides such that ceramide 3 is lower in the lesional AD and psoriasis skin as compared to healthy, while ceramide 2 showed a contrasting trend of decrease in lesional AD and increase in lesional psoriasis as opposed to healthy skin. Amount of cholesterol was significantly higher in lesional psoriasis as compared to lesional AD and healthy skin. These differences can aid in an objective classification of the skin conditions and in the formulation of new disease-specific topical treatments.