Relevant properties of gold nanoparticles, such as stability and biocompatibility, together with their peculiar optical and electronic behavior, make them excellent candidates for medical and biological applications. This review describes the different approaches to the synthesis, surface modification, and characterization of gold nanoparticles (AuNPs) related to increasing their stability and available features useful for employment as drug delivery systems or in hyperthermia and photothermal therapy. The synthetic methods reported span from the well-known Turkevich synthesis, reduction with NaBH4 with or without citrate, seeding growth, ascorbic acid-based, green synthesis, and Brust–Schiffrin methods. Furthermore, the nanosized functionalization of the AuNP surface brought about the formation of self-assembled monolayers through the employment of polymer coatings as capping agents covalently bonded to the nanoparticles. The most common chemical–physical characterization techniques to determine the size, shape and surface coverage of AuNPs are described underlining the structure–activity correlation in the frame of their applications in the biomedical and biotechnology sectors.

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World population growth, with the consequent consumption of primary resources and production of waste, is progressively and seriously increasing the impact of anthropic activities on the environment and ecosystems. Environmental pollution deriving from anthropogenic activities is nowadays a serious problem that afflicts our planet and that cannot be neglected. In this regard, one of the most challenging tasks of the 21st century is to develop new eco-friendly, sustainable and economically-sound technologies to remediate the environment from pollutants. Nanotechnologies and new performing nanomaterials, thanks to their unique features, such as high surface area (surface/volume ratio), catalytic capacity, reactivity and easy functionalization to chemically modulate their properties, represent potential for the development of sustainable, advanced and innovative products/techniques for environmental (bio)remediation. This review discusses the most recent innovations of environmental recovery strategies of polluted areas based on different nanocomposites and nanohybrids with some examples of their use in combination with bioremediation techniques. In particular, attention is focused on eco-friendly and regenerable nano-solutions and their safe-by-design properties to support the latest research and innovation on sustainable strategies in the field of environmental (bio)remediation.

This review presents current literature on different nanocomposite coatings and surface finishing for textiles, and in particular this study has focused on smart materials, drug-delivery systems, industrial, antifouling and nano/ultrafiltration membrane coatings. Each of these nanostructured coatings shows interesting properties for different fields of application. In this review, particular attention is paid to the synthesis and the consequent physico-chemical characteristics of each coating and, therefore, to the different parameters that influence the substrate deposition process. Several techniques used in the characterization of these surface finishing coatings were also described. In this review the sol–gel method for preparing stimuli-responsive coatings as smart sensor materials is described; polymers and nanoparticles sensitive to pH, temperature, phase, light and biomolecules are also treated; nanomaterials based on phosphorus, borates, hydroxy carbonates and silicones are used and described as flame-retardant coatings; organic/inorganic hybrid sol–gel coatings for industrial applications are illustrated; carbon nanotubes, metallic oxides and polymers are employed for nano/ultrafiltration membranes and antifouling coatings. Research institutes and industries have collaborated in the advancement of nanotechnology by optimizing conversion processes of conventional materials into coatings with new functionalities for intelligent applications.

Geopolymers are inorganic materials that form long-range, covalently bonded, networks; they are materials similar to ceramics, whose components are mainly aluminium and silicates. Any inorganic source of silica and alumina, dissolved in the alkaline solution, acts as a precursor of geopolymers. The type of clays most commonly used in the synthesis of geopolymers is based on kaolinite. The present work concerns the modification of the geopolymer at the chemical and nanostructural level, through the design and development of hybrid coating sol-gel formulations to improve characteristics such as mechanical strength, chemical inertness, heat resistance and porosity for possible use in the restoration and conservation of cultural heritage. The methods of functionalization of the geopolymers here shown are: (i) the treatment of the geopolymeric surface, post-drying, through the application of the sol-gel directly on the monolith, for a modification of the surface properties; (ii) the pretreatment of the geopolymeric mixture, through the addition of the alkoxysilane which can induce a homogeneous consolidation of the molecular structure, implementing the properties of the entire monolith. The employed alkoxysilanes differ according to the length of the hydrocarbon chain and the presence of halogen atoms. Hydrophobicity tests were performed on these formulations.

In recent years thanks to the Internet of Things (IoT), the demand for the development of miniaturized and wearable sensors has skyrocketed. Among them, novel sensors for wearable medical devices are mostly needed. The aim of this review is to summarize the advancements in this field from current points of view, focusing on sensors embedded into textile fabrics. Indeed, they are portable, lightweight, and the best candidates for monitoring biometric parameters. The possibility of integrating chemical sensors into textiles has opened new markets in smart clothing. Many examples of these systems are represented by color-changing materials due to their capability of altering optical properties, including absorption, reflectance, and scattering, in response to different external stimuli (temperature, humidity, pH, or chemicals). With the goal of smart health monitoring, nanosized sol–gel precursors, bringing coupling agents into their chemical structure, were used to modify halochromic dyestuffs, both minimizing leaching from the treated surfaces and increasing photostability for the development of stimuli-responsive sensors. The literature about the sensing properties of functionalized halochromic azo dyestuffs applied to textile fabrics is reviewed to understand their potential for achieving remote monitoring of health parameters. Finally, challenges and future perspectives are discussed to envisage the developed strategies for the next generation of functionalized halochromic dyestuffs with biocompatible and real-time stimuli-responsive capabilities.

Bacterial colonization of surfaces is the leading cause of deterioration and contaminations. Fouling and bacterial settlement led to damaged coatings, allowing microorganisms to fracture and reach the inner section. Therefore, effective treatment of surface damaged material is helpful to detach bio-settlement from the surface and prevent deterioration. Moreover, surface coatings can withdraw biofouling and bacterial colonization due to inherent biomaterial characteristics, such as superhydrophobicity, avoiding bacterial resistance. Fouling was a past problem, yet its untargeted toxicity led to critical environmental concerns, and its use became forbidden. As a response, research shifted focus approaching a biocompatible alternative such as exciting developments in antifouling and antibacterial solutions and assessing their antifouling and antibacterial performance and practical feasibility. This review introduces state-of-the-art antifouling and antibacterial materials and solutions for several applications. In particular, this paper focuses on antibacterial and antifouling agents for concrete and cultural heritage conservation, antifouling sol–gel-based coatings for filtration membrane technology, and marine protection and textile materials for biomedicine. In addition, this review discusses the innovative synthesis technologies of antibacterial and antifouling solutions and the consequent socio-economic implications. The synthesis and the related physico-chemical characteristics of each solution are discussed. In addition, several characterization techniques and different parameters that influence the surface finishing coatings deposition were also described.

Biofouling has destructive effects on shipping and leisure vessels, thus producing severe problems for marine and naval sectors due to corrosion with consequent elevated fuel consumption and higher maintenance costs. The development of anti-fouling or fouling release coatings creates deterrent surfaces that prevent the initial settlement of microorganisms. In this regard, new silica-based materials were prepared using two alkoxysilane cross-linkers containing epoxy and amine groups (i.e., 3-glycidyloxypropylmethyldiethoxysilane and 3-aminopropyltriethoxysilane, respectively), in combination with two functional fluoro-silane (i.e., 3,3,3-trifluoropropyl-trimethoxysilane and glycidyl-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononylether) featuring well-known hydro repellent and anti-corrosion properties. As a matter of fact, the co-condensation of alkoxysilane featuring epoxide and amine ends, also mixed with two opportune long chain and short chain perfluorosilane precursors, allows getting stable amphiphilic, non-toxic, fouling release coatings. The sol–gel mixtures on coated glass slides were fully characterized by FT-IR spectroscopy, while the morphology was studied by scanning electron microscopy (SEM), and atomic force microscopy (AFM). The fouling release properties were evaluated through tests on treated glass slides in different microbial suspensions in seawater-based mediums and in seawater natural microcosms. The developed fluorinated coatings show suitable antimicrobial activities and low adhesive properties; no biocidal effects were observed for the microorganisms (bacteria).