Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation followed by Langmuir–Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.

2D-Pyrophyllite, a layered material with notable physico-chemical properties, is suitable for various applications, such as electrical insulator, protective coating or lubricant. Liquid-phase exfoliation (LPE) has emerged as a promising, large-scale, low-cost method for obtaining substantial yields of high-quality, basal plane defect-free pyrophyllite flakes in dispersion. Optimizing exfoliation conditions is crucial for achieving these objectives. After adjusting experimental parameters (initial concentration of bulk material, sonication time, solvent type, and centrifugation rate), a stable pyrophyllite dispersion with a high concentration of 98.8 µg/mL was obtained. The LPE method enables the production of high-yield flakes with well-defined shapes, flat surfaces, and regular edges.

The 16th-century wall paintings of Monastery Crna Reka in Serbia are visibly deteriorating. Extensive wall degradation causes these frescoes to fall from their original positions and shatter into fragments. To address the proper restoration and conservation procedures, we examine the structure and morphology of the fragments. Micro-Raman spectroscopy and XRF revealed that the blue color on the wall paintings does not originate from blue pigments but results from the layer-by-layer technique of hematite and carbon black pigments by the artist, which, in combination with the mortar, gave a blue color sensation. Cross-sectional profiles and 3D maps obtained by profilometry show the surface morphology of these fragments, and can be consider as guidelines for further understanding of the various aspects of the painting’s creation, monitoring future degradation process, and developing or applying protective coatings for Serbian frescoes.

We investigated the wettability of Langmuir-Blodgett films from liquid phase exfoliated graphene. By applying cascade centrifugation, dispersions with size-selected flakes are obtained, and depending on the selected dispersion for film formation, films with different defect density are produced. We determined the wettability of our films by measuring the contact angle (CA). Films with the highest defect density, produced by the self-organization of smaller-sized and thinner graphene flakes, exhibited the highest wettability, with a CA of 77°. Conversely, films produced from dispersions with larger nanosheet dimensions demonstrated a hydrophobic nature, with a CA of 90°. This suggests that the wettability of our films can be adjusted by varying the size of the nanosheets used for film formation. Controlling the defect density and wettability of self-assembled graphene films allows the optimization of their properties for various application, particularly in wearable electronics.