The Orthographia Pratica de Varias Letras is a unique 17th-century Portuguese codex, notable for its exceptional significance in the history of Latin calligraphy during the Modern period. Unfortunately, it faces complex conservation challenges due to the presence of iron gall ink (IGI). This work aimed to thoroughly characterise the inks and their impact on the manuscript using an integrated analytical approach. Extensive micro-XRF analysis revealed two distinct groups of IGIs based on their transition metal content. Zn-rich IGIs were found in half of the manuscript, suggesting the use of Zn-bearing green vitriol. In contrast, a more refined form of green vitriol was identified in the IGIs on the other half, suggesting that different types of vitriol were used. Variations in the binder-to-vitriol ratios were proposed, indicating distinct IGI formulations throughout the codex. The poor condition observed in some folios was primarily associated with greater ink coverage per surface area and lower binder content. FIB-SEM and PIXE analysis provided insights into the behaviour of Fe within the cellulose structure, including penetration and lateral migration. The IGI chromophore was further investigated by M & ouml;ssbauer and XPS, which confirmed an Fe(III)-polyphenol mono-complex with a catecholate binding mode and Fe(III) in an octahedral arrangement. (c) 2026 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Polyoxometalates (POMs) – molecular metal–oxide clusters composed of charged metal–oxygen polyhedra formed via solution self‐assembly processes – exhibit diverse and highly useful structure–property–reactivity relationships in the various states of matter. Found in both mineral phases and biological systems, POM motifs have played supporting roles in research areas recognized by Nobel Prizes, including structural biology and porous framework chemistry. Although their translation into real‐world technologies still requires higher levels of technological readiness, POMs are currently being explored across a wide range of interdisciplinary fields. This work builds on the collective efforts of the global POM research community, which continues to generate both fundamental insights and innovative applications. Here, we present a comprehensive survey of POM research and outline future horizons in synthesis and characterization, with particular emphasis on recent breakthroughs and emerging directions. Four thematic domains – Health, Electronics, Energy, and the Environment – are used as an organizing framework to identify key shared principles and cross‐disciplinary opportunities in POM research. The goal of this work is to consolidate international efforts, foster cross‐disciplinary collaboration, and accelerate the development of application‐ready POM materials.

Iron gall inks (IGIs) played a central role as a writing medium in Western countries, leaving behind a vast legacy and significant conservation challenges. This study presents a twofold methodological approach to investigate the physicochemical behaviour of IGI-based formulations found in historical Portuguese sources. Fresh and 6-month naturally aged precipitates and supernatant solutions (dried inks) were characterised, and the impact of IGIs on Whatman paper over ageing was studied using attenuated total reflectance Fourier-transform infrared (ATR-FT-IR) spectroscopy, Raman and Mössbauer spectroscopies and X-ray diffraction (XRD). Iron(II) sulphates comprised the primary crystalline phase in the precipitates, while the dried inks consisted of distinct Fe(III)-polyphenol (PPh) complexes. Over time, Fe(III) Mössbauer parameters supported complex structural alterations. IGI-induced degradation on aged mockups was attested by Fe(II) oxalate formation until total depletion of the Fe(III)-PPh fraction. pH, ATR-FT-IR and degree of polymerisation analyses suggested that cellulose oxidation is the primary degradation mechanism, and the physical properties and XRD corroborated that the cellulose structure became disordered over ageing. The ink with the higher weight ratio of Fe(II) sulphate:gallnuts (unbalanced) exhibited the most aggressive action on the support. The results confirm that the more unbalanced the ink composition, the more severe its impact, with ink concentration per surface area also being a critical factor in paper decay.

Corrosion of metals and other materials in marine environments poses significant economic, operational, safety, and environmental challenges across the oil and gas industry, the renewable energy sector, and maritime infrastructure. Microbiologically influenced corrosion (MIC) accounts for a substantial portion of this corrosion, with sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) being key contributors. Conventional methods such as cathodic polarization have proven insufficient in mitigating the colonization of corrosive microbial communities in real marine environments, requiring the development of alternative, broad-spectrum antimicrobial strategies to prevent such biofilm formation. Recently, molybdate has emerged as a potential alternative to traditional biocides and nitrate. Our hypothesis is polyoxometalate-ionic liquids (POM-ILs), which exhibit antimicrobial and anticorrosion properties, could have a broader spectrum of antimicrobial activity than demonstrated until now and could be capable of shielding and protecting sensitive metal surfaces from the extreme acidic environments produced by MIC microorganisms. Here we show how two prototype polyoxomolybdate-based POM-ILs, [(CH3(CH2)6)4N]2[Mo6O19] and [(CH3(CH2)6)4N]4[Mo8O26], demonstrated antimicrobial activity at microgram per millilitre concentrations, prevented biofilm formation on metal surfaces, and provided resistance to corrosive acidic environments. Furthermore, impedance measurements were commensurate with electron microscopy studies showing that POM-IL-coated brass coupons withstood extremely corrosive environments. These proof-of-concept results demonstrate how multi-functional POM-IL coatings represent promising MIC mitigation solutions by providing a hydrophobic acid-resistant and biocidal protective layer that prevents biocolonisation and acidic corrosion by MIC microorganisms.

Micro- and nanoplastics (MNPs) are accumulating worldwide, posing a threat to ecosystems and biodiversity due to the ongoing global demand. In the literature there is a wide variety of procedures for sampling and characterizing MNPs in water samples, highlighting a lack of standardized methods, particularly plastics in the nanometric range (<0.1 μm), which require the removal of larger particles (>1.0 μm) followed by a concentration step to reach the quantification limits of analytical techniques. Proper sampling is essential for collecting representative samples, followed by a pre-treatment to remove suspended particles, which may interfere in the subsequent analysis. Consequently, specific techniques are employed to isolate the MNPs from the matrix samples and proceed to visual and chemical characterization. This review compiles key data on MNP characterization and advocates for a “best practices” toolbox to overcome current challenges, proposing a conceptual framework for developing efficient MNP characterization and supporting potential decontamination technologies.

Artificial lighting, essential for geotouristic purposes in subterranean sites, has facilitated the growth of colored photosynthetic organisms (lampenflora) on monumental 19th century bas-reliefs of the Pommery Champagne cellar-a UNESCO-protected heritage site-causing significant aesthetic and physical deterioration. To sustainably preserve these stone artworks, biocidal polyoxometalate-ionic liquids (POM-ILs) are tested alongside the commercial biocide Preventol RI80 on three trial zones: cleaned and colonized areas of a wall and clean stone samples positioned on a testing station within the cellar. After 1 year, untreated control areas exhibit growth/regrowth of biofilms, whereas surfaces treated with POM-ILs or Preventol RI80 remain biofilm free. Measurements of colorimetry and chlorophyll fluorescence confirm the effectiveness of both biocides in controlling photosynthetic micro-organisms. However, confocal fluorescence microscopy highlights a reduced long-term inhibition by Preventol RI80 compared to POM-ILs, despite the latter being applied at lower concentrations. Metagenomic analysis further validates the performance of POM-ILs, showing a notable decrease in microbial richness and diversity in treated areas. While both products effectively inhibit phototrophs and fungi, their efficacy against Pseudomonadota is limited, likely due to microbial adaptation via antibiotic resistance genes. This study underscores the potential of POM-ILs as a sustainable alternative for preserving cultural heritage against microbial colonization.

Invasive fungal infections kill more than 1.7 million and affect over a billion people each year; however, their devastating impact on human health is not widely appreciated and frequently neglected by public health authorities. In 2022, the WHO highlighted the urgent need for efficient diagnostic tests as well as safe and effective new compounds, drugs, and vaccines. Our hypothesis was that the naturally occurring polymer chitosan (CS) could be combined with molecular polyoxometalates (POMs) to produce POM@CS hybrid materials to promote broad-spectrum activity and habilitate synergic effects, which will ultimately help to prevent the appearance of resistances. Here we report the synthesis, characterisation, and antimicrobial activity of POM@CS hydrogels. Spectroscopic (FT-IR & EDS) and electron microscopy (SEM & TEM) techniques revealed the structural composition and morphology of the hybrid materials, whilst dynamic mechanical analysis demonstrated that the mechanical properties of the hydrogels were stable between pH 2 and 10 and were highly resistant to acidic conditions. The POM@CS hydrogels were active against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacteria, and proved to completely reduce fungal growth of Aspergillus niger and Cladosporium cladosporioides. Furthermore, the antimicrobial activity of the hydrogels could be enhanced through the inclusion of naturally occurring antimicrobial agents such as eugenol and cinnamaldehyde. Altogether, the development of such surface-active antimicrobial hydrogels pave the way to functional materials that can prevent biofilm formation in health and environmental applications and contribute to reducing the spread of antimicrobial resistance.

Iron gall ink (IGI), renowned for its indelibility, was the most important writing ink in the Western world from the 15th to the late 19th century. However, it is now known that IGIs induce acid-catalyzed hydrolysis and iron-catalyzed oxidation of the cellulose in historical paper documents. These mechanisms of deterioration cause significant damage to the writing support materials, including color alteration and burn-through appearance, and in the worst scenarios, physical disintegration of the supports. Minimally invasive, long-term effective conservation treatments that tackle the underlying mechanisms of IGI degradation and their corrosion effects are yet to be developed. This study introduces the deployment of hydrophobic and anticorrosive polyoxometalate-ionic liquids (POM-ILs) as colorless coatings to counteract IGI-corrosion of cellulosic supports. Model IGI-containing papers (mockups) were prepared, coated with POM-ILs, and artificially aged to assess the compatibility of POM-ILs with IGI-containing documents. Comprehensive monitoring using colorimetric and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM/EDS) analyses showed minimal interference with the aesthetic properties and morphology of the IGI mockups. In addition, polyoxometalates (POMs) with vacant metal atom sites in the cluster shell can be used to coordinate free transition metal ions. The ability of a monolacunary Keggin-type polyoxotungstate to coordinate free Fe(II) from IGI solution was demonstrated using UV-vis analysis. This led to the formation of a dimeric species, [(SiW11O39Fe)2O]K12·28H2O, which was characterized by single-crystal X-ray diffraction. Altogether, this study points to POM-ILs as promising protective coatings for effectively preserving historical IGI-written heritage.

In recent years, 3D printing has undergone a significant transformation, expanding beyond its initial niche applications, such as rapid prototyping and hobbyist projects. This evolution has been characterized by advancements in equipment, software, and, most notably, materials. However, the development of materials that present high-resolution and advanced tunable functionalities is still a challenge. Herein, we report the development of modular 3D-printable antimicrobial polymeric ionic liquid (PIL) scaffolds with in situ formation of copper-based nanoparticles within the polymeric matrix (Cu@PILs). A variety of formulations were specially designed and optimized to be printed by digital light processing and masked stereolithography techniques at high resolution. The antimicrobial activity as well as the biocompatibility of the different formulations was tested, changing the monomeric ionic liquid and the photoinitiator. Tailor-made objects were successfully manufactured, and as a demonstrator, a geometry compatible with a medical stent was printed.

New gold(I) complexes with coordination to 5-fluorouracil (5-FU), an anticancer drug with antibacterial properties, have been synthesised and characterised, and are the first reported examples of 5-FU-Au compounds. These new complexes show high solution stability, even in the presence of a cysteine derivative, and so were evaluated as antibacterial compounds against model Gram-positive and Gram-negative bacteria. All the complexes show excellent antibacterial activity against Gram-positive B. subtilis, most of them improving the activity of 5-FU alone. Furthermore, these new complexes are also active against Gram-negative E. coli, where [Au(5-FU)(PTA)], the complex with the smallest phosphane, is the most bactericidal, 32 times more active than 5-FU on its own.

Rock-based materials exposed to outdoor environments are naturally colonised by an array of microorganisms, which can cause dissolution and fracturing of the natural stone. Biocolonisation of monuments and architectures of important cultural heritage therefore represents an expensive and recurring problem for local authorities and private owners alike. In this area, preventive strategies to mitigate biocolonisation are generally preferred to curative approaches, such as mechanical cleaning by brush or high-pressure cleaning, to remove pre-existing patina. The aim of this work was to study the interaction between biocidal polyoxometalate-ionic liquid (POM-IL) coatings and calcareous stones and evaluate the capacity of these coatings to prevent biocolonisation through a series of accelerated ageing studies in climate chambers, carried out in parallel with a two-year period of outdoor exposure in north-eastern France. Our experiments show that POM-IL coatings did not affect water vapour transfer nor significantly alter the total porosity of the calcareous stones. Simulated weathering studies replicating harsh (hot and wet) climatic weather conditions demonstrated that the colour variation of POM-IL-coated stones did not vary significantly with respect to the natural uncoated stones. Accelerated biocolonisation studies performed on the weathered POM-IL-coated stones proved that the coatings were still capable of preventing colonisation by an algal biofilm. However, a combination of colour measurements, chlorophyll fluorescence data, and scanning electron microscopy imaging of stones aged outdoors in northern France for two years showed that coated and uncoated stone samples showed signs of colonisation by fungal mycelium and phototrophs. Altogether, our results demonstrate that POM-ILs are suitable as preventative biocidal coatings for calcareous stones, but the correct concentrations must be chosen to achieve a balance between porosity of the stone, the resulting colour variation and the desired duration of the biocidal effect over longer periods of time, particularly in outdoor environments.

Too little is known about areia de escrever, i.e., blotting sands, the intriguing particles sprinkled on freshly written scripts to accelerate the drying time of the ink. Blotting sands constitute a valuable but underestimated historical source. This work investigated the blotting sands used on the account books of the religious houses scattered across continental Portugal and Madeira Island (16th-19th centuries). The sands were mainly composed of different minerals, predominately black sands, but in a few cases, minerals were found mixed with gums, paper cocoons or bone shavings. The combined use of SEM-EDS, µ-Raman and FT-IR techniques uncovered the materials' chemical or mineralogical composition and morphology. This approach, allied with image analysis and statistics complemented with multivariate analysis, allowed us to look for trends between the samples and hypothesise about their provenance. Heavy minerals, such as ilmenite, hematite and almandine, were identified as major components, together with other silicates (e.g. quartz). Samples were dominated by medium-sized grains with shape features indicating texturally mature sediments resulting from a medium-to-long sedimentary transport. Due to shorter geological transport distances, Madeira Island was the exception, with more angular grains. This work allowed us to uncover blotting sands, value them as historical sources, and establish a roadmap for their use in Portugal, aiming to pave the way towards a more global context in Europe.

Historical and archival research focused on the Portuguese Inquisition documents (1551-1800) uncovered the use of arena known as blotting sands, a writing accessory used to hasten ink drying. We present in this work the first systematic study combining image analysis, SEM/EDS and mu-Raman techniques, statistics and chemometrics to characterise the blotting sands used by the Portuguese Inquisition and hypothesise their provenance. Iron-titanium and iron oxide minerals categorised as texturally mature sands are the dominant species, consistent with sediment extraction from fluvial or beach contexts and later processed. Chemometrics unveiled time period trends by clustering the samples according to morphology and composition data. This work constitutes a groundbreaking step towards uncovering this intricate writing tool. (c) 2023 The Author(s). Published by Elsevier Masson SAS on behalf of Consiglio Nazionale delle Ricerche (CNR). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

EDITORIAL article Front. Chem., 09 August 2022Sec. Inorganic Chemistry https://doi.org/10.3389/fchem.2022.977317

A substantial part of our written heritage is threatened by the fact that much of it has been written using iron-gall ink (IGI). One such example is the documents of the Portuguese Inquisition Tribunals, held by the Arquivo Nacional da Torre do Tombo. Here we present the first systematic analytical approach, using SEM/EDS, µ-FT-IR-ATR and µ-Raman techniques, to characterise fragments from historical records of the Inquisition Tribunals of Évora, Lisboa and Coimbra from the 16th to 18th centuries. The writing ink was identified as IGI, providing complementary compositional data and establishing differences between various formulations of the ink. Additionally, the deleterious effects of the inks-associated degradation phenomena were highlighted. This work allowed understand the writing inks used by this Portuguese institution.

Widespread use of plastics poses a serious environmental hazard to our planet and should be substituted by ecofriendly and biodegradable alternatives, simultaneously reducing waste of perishable food products and the risk of transmission of pathogenic microbes. In our study, we describe how the water solubility of the antimicrobial surfactant ethyl lauroyl arginate (LAE) can be reduced through complexation with a Keggin-type polyoxometalate (POM), K-8[SiW11O39]. The POM-LAE complex, LAE(7)K[SiW11O39], was effective against Listeria monocytogenes (L. monocytogenes) and Escherichia coli (E. coli) with minimal inhibitory concentrations (MICs) of 32 and 64 mu g/mL, respectively, with the important finding that the concentrations of LAE required to inhibit bacterial growth were as much as two times lower in the POM-LAE complex, compared with LAE on its own. In addition, our results demonstrate that POM-LAE is both an effective inhibitor of biofilm formation and is also able to destroy pre-formed biofilms of L. monocytogenes and E. coli at MIC concentrations. Further, POM-LAE was incorporated into carboxymethyl cellulose (CMC) films that were able to reduce 7-8 log (CFU/mL) of L. monocytogenes at concentrations of 5-10% POM-LAE. In vivo assays of the POM-LAE-CMC films with cured ham prevented initialk bacterial growth with a 0.77 log significative reduction in bacterial counts. Overall, this work provides new alternatives for the development of antimicrobial biodegradable films for ready-to-eat (RTE) foods prone to contamination with pathogenic bacteria, such as L. monocytogenes, while also circumventing practical issues related to the incorporation of LAE into active packaging films.

Developing artificial metalloenzymes that possess a superior performance to their natural counterparts is an attractive concept. Polyoxometalates (POMs) are a class of anionic molecular metal-oxides with excellent redox properties and bioactivity. We have recently introduced "POMlymers" - covalently conjugated POM-peptide hybrid materials - where the polypeptide chain is obtained through a ring-opening polymerisation (ROP) of α-amino acid N-carboxyanhydrides (NCA) on an inorganic POM scaffold. Attracted by the idea of preparing artificial metalloenzymes, here we report the supramolecular self-assembly of POMlymer hybrids into nanoparticles where an optimal environment for catalysis is created. Our results demonstrate that the self-assembly of covalent POMlymers, enhances the peroxidase-like activity of the parent POM anion whereas, in contrast, the catalytic activity for nanoparticles obtained by ionic self-assembly of the same peptide and POM components practically disappears. Furthermore, POMlymer nanoparticles also present antimicrobial and antibiofilm activity against the skin bacterium Staphylococcus epidermidis; whereas, ionic POM-peptide hybrids significantly increase biofilm production and endogenous production of reactive oxygen species. In summary, we present the self-assembly of POMlymer hybrids into nanoparticles and a combination of peroxidase activity and microbiology assays that show that the POM-peptide covalent bond is essential for the stability of the self-assembled nanoparticles and therefore for their catalytic and biological activity.

The increasing resistance of pathogenic microorganisms against common treatments requires innovative concepts to prevent infection and avoid long-term microbe viability on commonly used surfaces. Here, we report the preparation of a hybrid antimicrobial material based on the combination of microbiocidal polyoxometalate-ionic liquids (POM-ILs) and a biocompatible polymeric support, which enables the development of surface coatings that prevent microbial adhesion. The composite material is based on an antibacterial and antifungal room-temperature POM-IL composed of guanidinium cations (N,N,N',N'-tetramethyl-N″, N″-dioctylguanidinum) combined with lacunary Keggin-type polyoxotungstate anions, [α-SiW11O39]8-. Integration of the antimicrobial POM-IL into the biocompatible, flexible, and stable polymer poly(methyl methacrylate) (PMMA) results in processable films, which are suitable as surface coatings or packaging materials to limit the proliferation and spread of pathogenic microorganisms (e.g., on public transport and hospital surfaces, or in ready-to-eat-food packaging).