This review offers an overview of the most recent research activities on counteracting the biodeterioration process of stone monuments, underlining all those aspects regarding eventual procedural drawbacks and compliance with sustainable criteria. For this purpose, the definition of “green conservation of cultural heritage” has been proposed. Its basics have been utilized in the text to highlight the issues arising from the most common conservative procedures as well as guidelines for the development of innovative technologies. The review then deals with the most innovative antimicrobial approaches, among which nano- and bio-technologies play a main role. Ionic liquids are a special class of salts, which can be prepared by applying Safe by Design concepts, to meet the Green Conservation criteria.

Optical detection of parts-per-million (ppm) levels of CO by a structurally well-defined monolayer consisting of bimetallic rhodium complexes on glass substrates has been demonstrated.

The potential of using poly(ionic liquid)s as a new family of hydrorepellent materials has been explored. Free-radical polymerization of a series of ionic liquids based on the polymerizable cation [2-(methacryloyloxy)ethyl]trimethylammonium and on the hydrophobic anions bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate and dodecylbenzenesulfonate led to the corresponding poly(ionic liquid)s that were characterized by TGA and DSC analysis, SEM, MALDI-TOF and XPS spectroscopy. Contact angle investigations show that the nature of the surface of the poly(ionic liquid)s based on the nonafluoro-1-butanesulfonate and dodecylbenzenesulfonate anions are featured by remarkable hydrophobic properties with advancing contact angles (θ_adv) lying in the range 113–118°, while to the polymer poly[2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethylsulfonyl)imide is associated poor hydrorepellent activity (θ_adv = 76°). The tensiometric measurements also experience receding contact angles (θ_rec) lying in the range 16–20° and a consequent high hysteresis suggesting that, on the outermost layers of the polymers, very high and very low-energy surface portions are present.

A series of polymerizable tetraalkylammonium ionic liquids based on [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium cation and bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anions, as well as their corresponding homo- and copolymers, have been synthesized and characterized by means of ¹H NMR, TG-DTA, DSC, MALDI-TOF, viscosimetry and XPS investigations. Hydrophobic and CO₂ sensing properties of the poly(ionic liquid)s have been explored by dynamic contact angle and quartz crystal microbalance measurements. The CO₂ sensing behavior of present polymers is very remarkable as they are featured by extremely rapid and completely reversible response without any memory-effect. Best results, in terms of sensitivity, have been obtained for [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium nonafluoro-1-butanesulfonate-based homopolymer. Tensiometric data show good hydrophobic properties with θ_adv > 90° for all the polymers under study except the one involving 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anion (θ_adv = 78.3°); receding contact angles, representative of the most hydrophilic portions of the polymers surface, lie in the range 22–54° and can be further improved by choosing the proper long-chained N-alkyl groups.