Pickering Emulsions Based on Wax and Halloysite Nanotubes: An Ecofriendly Protocol for the Treatment of Archeological Woods

A thermosensitive luminescence halloysite-based nanocomposite enabling encryptable thermal printing

In situ formation of carbon dots on halloysite nanotubes is demonstrated by treating polyacrylamide-grafted halloysite nanotubes with polycarboxylic acid without the recourse to extremely high temperatures or solvents. Thermosensitive luminescence and phosphorescence properties are carefully investigated. The polyacrylamide-grafted halloysite nanotubes are further processed as composite films for encryptable thermal printing.

Halloysite nanotubes as nano-support matrix for programming the photo/H2O dual triggered reversible gel actuator

Gel actuators are a kind of soft intelligent material that can convert external stimuli into deformations to generate mechanical responses. The development of gel actuators with advanced structures to integrate multiple responsiveness, programmability, and fast deformation ability is urgently needed. Here, we explored a poly(7-(2-methacryloyloxyethoxy)-4-methylcoumarin-co-acrylic acid-co-glycol) ternary gel network as an actuator with reprogrammable photo/H2O dual responsibilities. In such a design, [2 + 2] photodimerization and photocleavage reactions of coumarin moieties can be realized under 365 and 254 nm light irradiation, respectively, affording reversible photodriven behaviour of the gels. The abundant carboxylic acid in the backbone has the capacity to form additional crosslinks to assist and accelerate the photodriven behaviour. The incorporation and orientation of halloysite nanotubes (HNTs) in gel matrices support an axial direction force and result in a more controllable and programmable actuating behaviour. The synergistic response enables fast grasping-releasing of 5-times the weight of the object in water within 10 min by fabricating HNT-incorporated gels as a four-arm gripper.

Preparation and characterization of carnauba wax-based particle with hierarchical structure and its use as hydrophobic coating for chitosan films

To improve the hydrophobicity of polysaccharide-based films, hydrophobic carnauba wax-based particles were prepared by Pickering emulsion. The influence of the different size of the particles on the structure and hydrophobicity of the chitosan coating films were investigated. The results showed that micro-scale particles (average particle size 25.04 μm) with nano-scale (5-10 nm) TiO2 uniformly distributed on the surface of the particles were formed by Pickering emulsion. The chitosan coating films showed higher contact angle and lower sliding angle compared to the control due to the hierarchical structure, hydrophobicity and arrangement of the particles. In addition, the small particle (23-48 μm) coating film showed higher hydrophobicity than the large particle coating film (48-70 μm) due to the small particle size and the formation of more small gaps. The gaps were conducive to form "air cushion" which reduced the contact area between water and the coating films and thus increased contact angle and decreased sliding angle. The coating films showed high chemical stability and low residual rates of liquid food. The results suggest that Pickering emulsion is an effective method to create wax-based particles with hierarchical structure and the particles have potential to be used as hydrophobic coating materials.

A ferroptosis-targeting ceria anchored halloysite as orally drug delivery system for radiation colitis therapy

Radiation colitis is the leading cause of diarrhea and hematochezia in pelvic radiotherapy patients. This work advances the pathogenesis of radiation colitis from the perspective of ferroptosis. An oral Pickering emulsion is stabilized with halloysite clay nanotubes to alleviate radiation colitis by inhibiting ferroptosis. Ceria nanozyme grown in situ on nanotubes can scavenge reactive oxygen species, and deferiprone was loaded into the lumen of nanotubes to relieve iron stress. These two strategies effectively inhibit lipid peroxidation and rescue ferroptosis in the intestinal microenvironment. The clay nanotubes play a critical role as either a medicine to alleviate colitis, a nanocarrier that targets the inflamed colon by electrostatic adsorption, or an interfacial stabilizer for emulsions. This ferroptosis-based strategy was effective in vitro and in vivo, providing a prospective candidate for radiotherapy protection via rational regulation of specific oxidative stress.

Highly Elastic and Anisotropic Wood-Derived Composite Scaffold with Antibacterial and Angiogenic Activities for Bone Repair

Scaffold-based tissue engineering is a promising strategy to address the rapidly growing demand for bone implants, but developing scaffolds with bone extracellular matrix-like structures, suitable mechanical properties, and multiple biological activities remains a huge challenge. Here, it is aimed to develop a wood-derived composite scaffold with an anisotropic porous structure, high elasticity, and good antibacterial, osteogenic, and angiogenic activities. First, natural wood is treated with an alkaline solution to obtain a wood-derived scaffold with an oriented cellulose skeleton and high elasticity, which can not only simulate collagen fiber skeleton in bone tissue but also greatly improve the convenience of clinical implantation. Subsequently, chitosan quaternary ammonium salt (CQS) and dimethyloxalylglycine (DMOG) are further modified on the wood-derived elastic scaffold through a polydopamine layer. Among them, CQS endows the scaffold with good antibacterial activity, while DMOG significantly improves the scaffold's osteogenic and angiogenic activities. Interestingly, the mechanical characteristics of the scaffolds and the modified DMOG can synergistically enhance the expression of yes-associated protein/transcriptional co-activator with PDZ binding motif signaling pathway, thereby effectively promoting osteogenic differentiation. Therefore, this wood-derived composite scaffold is expected to have potential application in the treatment of bone defects.

Study on the Wood Characteristics of the Chinese Ancient Ship Luoyang I

Luoyang No.1 is a Qing Dynasty (1644-1902) inland river ancient wooden shipwreck discovered in September 2013. It adds significantly to the study of Grand Canal transport history and Luoyang's economic history. The wood characteristics of Luoyang No.1 were investigated in this study using chemical compositions, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nano-indentation (NI), and scanning electron microscopy (SEM). The results showed that the holocellulose content was only 32.84-37.69%, indicating that the cellulose and hemicellulose had been seriously degraded. Based on the XRD pattern, the degree of crystallinity of cellulose in wood ranged from 19.82 to 22.83%. The nano-indentation demonstrated that compared with the undegraded contemporary wood, the elastic modulus and hardness of the ancient ship wood decreased by 45.5% and 32.1%, respectively. Furthermore, the FTIR spectra revealed that the biological deterioration of ancient wood was indicated by a decrease in the peaks related to cellulose and hemicellulose, but the change in lignin was insignificant. The results could provide knowledge for appropriate dewatering, strengthening, restoration strategies and regulation of the museum environment.

Soap-Free Emulsion Composed of Polymer Solutions and an Aqueous Clay Suspension

Novel emulsification was found in the system of aqueous suspension of a clay mineral (a synthetic hectorite) and a solution of polyvinyl butyral in 1-butanol without using surface-active agents. Droplets of the oil phase exhibited different sizes depending on the concentration of polyvinyl butyral solution and aqueous clay suspension. Shearing force produced from the high viscosity of the clay suspension was a factor to lead oil droplets to size smaller. The clay mineral was confirmed to be in the water phase, not at the oil and water interface. The emulsion showed useful thermal stability up to 80 °C. The present emulsion was successfully applied as a platform of the photochromic reaction of spiropyran.

Characteristics of Ancient Shipwreck Wood from Huaguang Jiao No. 1 after Desalination

Huaguangjiao I refers to the ancient Chinese wooden shipwreck of the South Song Dynasty (1127-1279 AD) discovered in the South China Sea in 1996. From 2008 to 2017, the archaeological waterlogged wood was desalted using deionized water combined with ultrasonic treatment, and desalted using EDTA-2Na, EDTAHO, and NaH₂PO₄·2H₂O solutions. In this paper, the degree of degradation of the modified waterlogged archaeological wood and the moisture and content of the main components were determined. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nanoindentation (NI), and scanning electron microscopy (SEM) were employed to investigate the state of wood degradation after desalination and desulfurization. The results showed that the water content of the wood was as high as 532~1149%, while the basic density was only 0.14~0.18 g/cm³, indicating that the wood had been seriously degraded. The holocellulose content was only 36-40%. Based on the XRD patterns, the degree of cellulose crystallinity in the modified wood was 14.08%. The elastic modulus and hardness of the ancient shipwreck wood after desalination and desulfurization were 1.28-4.31 and 0.10-0.28 GPa, respectively, according to nanoindentation. In addition, the FTIR spectra revealed that the biological deterioration of the modified wood caused cellulose and hemicellulose degradation, but no apparent lignin alteration occurred. The results could provide knowledge for appropriate dewatering, strengthening, and restoration strategies.

Natural Amphiphilic Shellac Nanoparticle-Stabilized Novel Pickering Emulsions with Droplets and Bi-continuous Structures

Shellac is a natural amphiphilic substance, and its nanoparticles can be used to stabilize Pickering emulsions with droplets and bi-continuous structures. In this study, shellac nanoparticles (SNPs) were produced through the anti-solvent method, and these SNPs were used to produce a series of Pickering emulsions. Fourier transform infrared results showed that SNPs were generated through hydrogen bonding and hydrophobic effects. The contact angle of SNPs was 122.3°, indicating that hydrophobicity was their dominant characteristic. According to the results of confocal laser scanning microscopy, the Pickering emulsions stabilized by SNPs showed oil-in-water, bi-continuous structure, and water-in-oil characteristics, which were dependent on the oil-phase content. The resistance value of the emulsified part of these Pickering emulsion systems significantly increased at an oil-phase ratio of 80-90% (more than 10⁵ MΩ), as compared with the 10-70% oil-phase content (around 1 MΩ). The viscosity of SNP-stabilized Pickering emulsions with bi-continuous structures was highest at 40% oil-phase content. The porous material prepared by using Pickering emulsions with bi-continuous structures as a template had an interconnected structure and was able to absorb both water and oil. This study indicated that these amphiphilic SNPs readily form bi-continuous structures and effectively stabilize Pickering emulsions with droplets. These SNPs are expected to have increased application in food and pharmaceutical industries.

Characteristics of Ancient Ship Wood from Taicang of the Yuan Dynasty

In this study, wood samples extracted from the Taicang ancient ship, dating back to the Yuan Dynasty, were investigated to study the characteristics of waterlogged archaeological wood. The macroscopic characteristics and microscopic structures were used to identify the wood species. To assess the degree of degradation of the waterlogged archaeological wood, X-ray diffraction (XRD), nanoindentation (NI), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to compare the new and ancient wood samples from the same species. The microscopic structures of the samples were identified as Pinus massoniana. The XRD and nanoindentation results revealed that the crystallinity index of the cellulose decreased from 41.07% to 33.85%, the elastic modulus was reduced by 20.90%, and hardness was reduced by 55.6% compared with the new wood. The FTIR spectra revealed that biological deterioration occurred in the cellulose and hemicellulose, but there was no noticeable change in the lignin content. These results provide helpful information for the conservation and restoration of ancient ships.

Exploring maleimide-anchored halloysites as nanophotoinitiators for surface-initiated photografting strategies

Maleimide-functionalized HNTs (HNTs-I) were prepared and explored as a nanophotoinitiator. Vinyl monomers can be grafted onto the nanotubes following a spatially controllable, metal-free and non-contact photoinitiated approach. The obtained HNTs-I were further used in a 3D printing system to fabricate hydrogels with designed configurations.

Thermal and Mechanical Characterization of Yarn Samples from Flemish Tapestry of the Sixteenth Century

We propose a physico-chemical approach for theharacterization of the conservation condition of yarns from a Flemish tapestry of the sixteenth century. The aging effect on the yarns' performance was evaluated by comparison with commercial materials. Water uptake experiments highlighted the aptitude of yarns toward water sorption and their increased hydrophilicity upon aging. Thermogravimetric analysis can be considered a fast approach for the fiber identification and assessment on the material life-time. The dynamic mechanical analysis provided direct evidence on the yarns, conservation state and their performance under different mechanical stresses. The proposed characterization path can be relevant for stating the condition of the tapestry and for designing a conservation protocol for the preservation of the artwork.

Improvement of Surface Coating and Interfacial Properties of Hot-Waxed Wood Using Maleic Anhydride Grafted Polypropylene Wax

Beeswax is used on wood furniture surfaces in China. Beeswax is expensive and has a low melting temperature, and the wax film is easily softened and destroyed. To overcome these problems, a modified polypropylene wax grafted with maleic anhydride, with a high melting temperature and low price, was used in hot-waxed wood. The adhesion, hardness, hydrophobic properties, heat resistance, color, and gloss of hot-waxed woods were also examined. The surface and interfacial properties were characterized by FTIR, XRD, and SEM. The modified polypropylene wax showed a higher melting temperature than beeswax by DSC, and the heat resistance of hot-waxed wood using it was revealed by TG. The adhesion for the modified polypropylene wax hot-waxed wood surface was shown to achieve grade 1. In addition, it maintained original grades in adhesion after soaking in water and was greater than beeswax hot-waxed wood. The hot-waxed wood surfaces become hydrophobic compared with untreated wood, and the hydrophobicity of the modified polypropylene wax hot-waxed wood surfaces, with a decreased water contact angle, were slightly weaker than beeswax hot-waxed wood and polypropylene wax hot-waxed wood. Moreover, in hardness, the modified polypropylene wax hot-waxed wood surfaces (2H) were harder than beeswax hot-waxed wood (3B), representing stronger scratch resistance and performing well in decorative characteristics, such as color and gloss. The results of SEM, FTIR, and XRD showed mechanical and weak chemical bonding between the waxes and the surface of the wood with the presence of wax in a wood structure. Therefore, the modified polypropylene wax could be used in hot-waxed wood with great heat resistance, adhesion, and surface performance. The study is beneficial for the application of wood coatings using synthetic wax in the future.

One-step, highly stable Pickering emulsions stabilized by ZnO: tuning emulsion stability by in situ functionalization

HYPOTHESIS

Oxide-stabilized emulsions generally require a surface functionalization step to tune the oxide wettability, often involving hazardous hydrophobizing agents. Here, we propose the in situ functionalization of ZnO in vegetable oils without the addition of any modifier, resulting in the one-step formation of highly stable Pickering emulsions.

EXPERIMENTS

The role of ZnO surface features was studied by modifying the particles' wettability through surface functionalization and by comparing different oil phases. The emulsion stability was assessed through aging tests, multiple hot-and-cold cycles, centrifugation, and addition of multiple electrolytes.

FINDINGS

While the wetting features of the functionalized oxide play a crucial role when the oil phase is methyl octanoate, emulsions based on vegetable oils form also using hydrophilic ZnO. During the emulsification, an in situ functionalization of bare ZnO particles takes place due to the fatty acids present in vegetable oil. These in situ-generated systems lead to stable emulsions showing < 2 μm-diameter oil droplets. The resulting emulsions display excellent stability over time (over seven months) and against temperature variations, mechanical stress and increased ionic strength. Finally, we demonstrate that this approach can be extended to a variety of vegetable oils and oxides with different morphologies.

Electrospun halloysite nanotube loaded polyhydroxybutyrate-starch fibers for cartilage tissue engineering

Articular cartilage is a connective load-bearing tissue with a low rate of regeneration due to slow metabolism. Fabricating tissue-like structure modified based on natural features can improve healing process. Fibrous scaffolds based on the composition of hydrophobic polyhydroxybutyrate (PHB) and hydrophilic starch reinforced using halloysite nanotubes (HNTs) with appropriate physico-chemical and biological properties was produced via electrospinning technique for long-term applications like cartilage regeneration. Textural properties were analyzed through SEM imaging that showed incorporating HNTs up to 2 wt% decreased mean fiber diameter to 158 ± 48 nm with larger pore size and appropriate porosity percentage. Moreover, the tensile strength was improved up to 4.21 ± 0.31 MPa after HNTs incorporation support chondrocyte cell growth. Furthermore, incorporating HNTs induced surface hydrophilicity and in vitro degradation. The biological assays both MTT assay and cell attachment of chondrocyte cells on 2 wt% HNTs incorporated into PHB-starch fibers indicated that HNTs incorporation can support cell growth and attachment without any toxicity for biomedical applications. To conclude, the obtained results demonstrated PHB-starch/HNTs fibrous scaffold could be potential for further experimental studies for tissue engineering applications like cartilage.

Printable Hydrogels Based on Alginate and Halloysite Nanotubes

The design of hydrogels for the controlled release of active species is an attractive challenge. In this work, we prepared hybrid hydrogels composed of halloysite nanotubes as the inorganic component, and alginate as the organic counterpart. The reported procedure allowed us to provide the resulting materials with a peculiar wire-like shape. Both optical and scanning electron microscopy were used to characterize the morphological properties of the hydrogel wires, whose diameters were ca. 0.19 and 0.47 mm, respectively. The possibility to be exploited as drug delivery systems was carried out by loading the nanoclay with salicylic acid and by studying the release profiles. Thermogravimetric experiments showed that the amount of encapsulated drug was 4.35 wt%, and the salicylic acid was thermally stabilized after the loading into the nanotubes, as observed by the shift of the degradation peak in the differential thermograms from 193 to 267 °C. The kinetics investigation was conducted using UV–Vis spectrophotometry, and it exhibited the profound effects of both the morphology and dimensions on the release of the drugs. In particular, the release of 50% of the payload occurred in 6 and 10 h for the filiform hydrogels, and it was slower compared to the bare drug-loaded halloysite, which occurred in 2 h. Finally, an induction period of 2 h was observed in the release profile from the thicker sample.

Evaluation of membrane tailored with biocompatible halloysite‒polyaniline nanomaterial for efficient removal of carcinogenic disinfection by‒products precursor from water

Humic acid (HA) is the main component of natural organic matter that generates carcinogenic by‒products during disinfection and its removal from water resources is challenging. Biocompatible halloysite (HNTs) nanomaterial decorated with polyaniline (HNTs‒PANI) was synthesized via polymerization technique. HNTs‒PANI was added to prepare polyethersulfone mixed matrix membranes (MMMs). The influence of HNTs‒PANI concentration on HA removal efficiency was studied by varying the HNTs‒PANI (0.5, 1 and 1.5 wt%). The characterization studies of MMMs revealed that the addition of HNTs‒PANI improved the morphology of the membranes, surface properties, chemical stability and thermal property. The amine and hydroxyl groups within the MMMs improved the membrane wettability. The addition of HNTs‒PANI within the MMMs had significantly enhanced the pure water flux and HA filtration. YHP2 MMM with 1 wt% of HNTs‒PANI demonstrated sieving coefficient of 0.10 and the highest HA removal efficiency of 91% greater than the neat PES membrane. Furthermore, the antifouling property of the MMMs was studied using HA as foulant. 1 wt% of HNTs‒PANI added MMM showed a high flux recovery ratio (94.9%) with low total fouling of 12% and low irreversible fouling of 5%, respectively. Thus, HNTs‒PANI was an efficient nanomaterial for enhancing the pure water flux, removal efficiency and antifouling property to treat water contaminated with HA.

Chitosan Functionalized with Carboxyl Groups as a Recyclable Biomaterial for the Adsorption of Cu (II) and Zn (II) Ions in Aqueous Media

The modification of chitosan represents a challenging task in obtaining biopolymeric materials with enhanced removal capacity for heavy metals. In the present work, the adsorption characteristics of chitosan modified with carboxyl groups (CTS-CAA) towards copper (II) and zinc (II) ions have been tested. The efficacy of the synthesis of CTS-CAA has been evaluated by studying various properties of the modified chitosan. Specifically, the functionalized chitosan has been characterized by using several techniques, including thermal analyses (differential scanning calorimetry and thermogravimetry), spectroscopies (FT-IR, XRD), elemental analysis, and scanning electron microscopy. The kinetics and the adsorption isotherms of CTS-CAA towards both Cu (II) and Zn (II) have been determined in the aqueous solvent under variable pH. The obtained results have been analyzed by using different adsorption models. In addition, the experiments have been conducted at variable temperatures to explore the thermodynamics of the adsorption process. The regeneration of CTS-CAA has been investigated by studying the desorption process using different eluents. This paper reports an efficient protocol to synthesize chitosan-based material perspective as regenerative adsorbents for heavy metals.

Barrier Dispersion-Based Coatings Containing Natural and Paraffin Waxes

Petroleum, synthetic, and natural waxes have been used as hydrophobic bases for dispersions intended for use as barrier coatings for packaging paper. Oil-in-water dispersions with alkaline pH were prepared by a two-step homogenization procedure containing paraffin wax, with various characteristics, the Fischer–Tropsch synthesis product or beeswax. The size of the dispersed particles determined by dynamic light scattering depended on the type of hydrophobic base used and was in the range of 350–440 nm. The ability of dispersion particles in aggregation driven by electrostatic attraction, evaluated by Zeta potential analysis by electrophoretic light scattering, was from −26 to −50 mV. Static multiply light scattering was used for 30 days of stability assessment and helped to select the dispersion with a Sarawax SX70 wax base as the most stable. Dispersions were further used for coating the backing of kraft paper by the Meyer rod method. Coated paper with an applied coating of 6 g/m² had very good hydrophobic properties (Cobb60 < 4 g/m²), sufficient strength properties, and air permeation, which enabled its application as a packaging material. The dispersions based on Sarawax SX70 wax were evaluated as the best coating for Mondi ProVantage Kraftliner 125 g/m² backing paper. Good hydrophobic properties and strength properties indicate the possibility of using the SX70-based wax dispersion coating as a replacement for PFAS coatings in some applications.

Recent Developments in the Application of Inorganic Nanomaterials and Nanosystems for the Protection of Cultural Heritage Organic Artifacts

Cultural heritage (CH) represents human identity and evidence of the existence and activities that people have left over time. In response to the action of aggressive degrading factors, different materials have been developed and used to protect cultural heritage artifacts. The discovery of optimal materials for this purpose also raises several problems, mainly related to their compatibility with the support material, the most important aspect being that they must preserve their aesthetic characteristics. In this context, the present review paper aims to provide a critical discussion about the possibilities of using different inorganic nanomaterials and recipes for the conservation of cultural heritage objects of organic nature (such as paper, wood, and other support materials). In addition, also are covered different aspect concerning protection mechanisms and application methods as well as future perspectives in this area.

Synergistic Study of Solid Lubricant Nano-Additives Incorporated in canola oil for Enhancing Energy Efficiency and Sustainability

In recent years, with the development of eco-friendly lubricants, different vegetable oils have been studied and found to improve the overall tribological performance compared to petroleum-based oils. Being one of the commonly used vegetable oils, canola oil has become popular due to its non-toxicity and low cost. However, this bio-lubricant lacks tribological performance compared to petroleum-based oils. To improve its performance, sustainable solid additives such as graphene nanoplatelet (GNP) and hexagonal boron nitride (hBN) have recently gained the researcher’s attention. While incorporating nanomaterials in the oil as additives is a promising way to improve base oil’s performance, the excessive use of nanoparticles can introduce undesirable effects. This study investigated canola oil’s tribological performances with the addition of 0.5, 1.0, 1.5, and 2.0 wt.% GNP and 0.5, 1.0, and 1.5 wt.% hBN nanoparticles. The dynamic viscosities of these seven settings showed higher viscosity for GNP-incorporated oils compared to that with hBN. The boundary lubrication regime was targeted for the coefficient of friction (COF) and wear analyses during each pin on the disk test. It was observed that for the GNP, 1.5 wt.% provided the minimum COF (52% less than base oil), whereas, for the hBN, 1.0 wt.% provided the lowest (40% less than base oil) values. Based on these insights, three nano lubricant mixtures were formulated by incorporating both GNP and hBN settings in different ratios. These mixtures provided an optimum positive synergy by reducing 56% friction and 90% wear compared to the base oil. These percentage values were significantly more compared to both GNP and hBN based lubricants in their individual settings. These improvements in the mixture were due to a composite film formed which protected the interacting surfaces and also due to the polishing mechanisms. Therefore, incorporating both these nanoparticles in canola oil could reduce friction and wear and thus help in better energy conservation.

Sustainability in Heritage Wood Conservation: Challenges and Directions for Future Research

Conserving the world’s cultural and natural heritage is considered a key contributor to achieving the targets set out in the United Nation’s Sustainable Development Goals, yet how much attention do we pay to the methods we use to conserve and protect this heritage? With a specific focus on wooden objects of cultural heritage, this review discusses the current state-of-the-art in heritage conservation in terms of sustainability, sustainable alternatives to currently used consolidants, and new research directions that could lead to more sustainable consolidants in the future. Within each stage a thorough discussion of the synthesis mechanisms and/or extraction protocols, particularly for bio-based resources is provided, evaluating resource usage and environmental impact. This is intended to give the reader a better understanding of the overall sustainability of each different approach and better evaluate consolidant choices for a more sustainable approach. The challenges facing the development of sustainable consolidants and recent research that is likely to lead to highly sustainable new consolidant strategies in the future are also discussed. This review aims to contribute to the ongoing discussion of sustainable conservation and highlight the role that consolidants play in truly sustainable heritage conservation.

Conversion of Organic Dyes into Pigments: Extraction of Flavonoids from Blackberries (Rubus ulmifolius) and Stabilization

The blackberry’s color is composed mainly of natural dyes called anthocyanins. Their color is red–purple, and they can be used as a natural colorant. Anthocyanins are flavonoids, which are products of plants, and their colors range from orange and red to various shades of blue, purple and green, according to pH. In this study, the chemical composition of an extract obtained from blackberries was defined by LC-ESI/LTQOrbitrap/MS in positive and negative ionization mode. Furthermore, we investigated the adsorption process of blackberry extract using several inorganic fillers, such as metakaolin, silica, Lipari pumice, white pozzolan and alumina. The pigments exhibit different colors as a function of their interactions with the fillers. The analysis of the absorption data allowed the estimation of the maximum adsorbing capacity of each individual filler tested. Through thermogravimetric measurements (TGA), the thermal stability and the real adsorption of the organic extract were determined.

The Viscoelastic Behaviour of Waterlogged Archaeological Wood Treated with Methyltrimethoxysilane

Waterlogged wood treatment with methyltrimethoxysilane (MTMS) proved effective in stabilising wood dimensions upon drying (anti-shrink efficiency of 76-93%). Before the method can be proposed as a reliable conservation treatment, further research is required that includes the evaluation of the mechanical properties of treated wood. The aim of the study was to characterise the effect of the treatment on the viscoelastic behaviour of archaeological waterlogged elm and oak wood differing in the degree of degradation. Dynamic mechanical analysis in the temperature range from -150 to +150 °C was used for the study. To better understand the viscoelastic behaviour of the treated wood, pore structure and moisture properties were also investigated using Scanning Electron Microscopy, nitrogen sorption, and Dynamic Vapour Sorption. The results clearly show that methyltrimethoxysilane not only prevents collapse and distortions of the degraded cell walls and decreases wood hygroscopicity (by more than half for highly degraded wood), but also reinforces the mechanical strength by increasing stiffness and resistance to deformation for heavily degraded wood (with an increase in storage modulus). However, the MTMS also has a plasticising effect on treated wood, as observed in the increased value of loss modulus and introduction of a new tan δ peak). On the one hand, methyltrimethoxysilane reduces wood hygroscopicity that reflects in lower wood moisture content, thus limiting the plasticising effect of water on wood polymers, but on the other hand, as a polymer itself, it contributes to the viscous behaviour of the treated wood. Interestingly, the effect of silane differs with both the wood species and the degree of wood degradation.

Sepiolite-Hydrogels: Synthesis by Ultrasound Irradiation and Their Use for the Preparation of Functional Clay-Based Nanoarchitectured Materials

Sepiolite and palygorskite fibrous clay minerals are 1D silicates featuring unique textural and structural characteristics useful in diverse applications, and in particular as rheological additives. Here we report on the ability of grinded sepiolite to generate highly viscous and stable hydrogels by sonomechanical irradiation (ultrasounds). Adequate drying of such hydrogels leads to low-density xerogels that show extensive fiber disaggregation compared to the starting sepiolite—whose fibers are agglomerated as bundles. Upon re-dispersion in water under high-speed shear, these xerogels show comparable rheological properties to commercially available defibrillated sepiolite products, resulting in high viscosity hydrogels that minimize syneresis. These colloidal systems are thus very interesting as they can be used to stabilize many diverse compounds as well as nano-/micro-particles, leading to the production of a large variety of composites and nano/micro-architectured solids. In this context, we report here various examples showing how colloidal routes based on sepiolite hydrogels can be used to obtain new heterostructured functional materials, based on their assembly to solids of diverse topology and composition such as 2D and 1D kaolinite and halloysite aluminosilicates, as well as to the 2D synthetic Mg,Al-layered double hydroxides (LDH).

Conservation of Waterlogged Wood—Past, Present and Future Perspectives

This paper reviews the degradation, preservation and conservation of waterlogged archaeological wood. Degradation due to bacteria in anoxic and soft-rot fungi and bacteria in oxic waterlogged conditions is discussed with consideration of the effect on the chemical composition of wood, as well as the deposition of sulphur and iron within the structure. The effects on physical properties are also considered. The paper then discusses the role of consolidants in preserving waterlogged archaeological wood after it is excavated as well as issues to be considered when reburial is used as a means of preservation. The use of alum and polyethylene glycol (PEG) as consolidants is presented along with various case studies with particular emphasis on marine artefacts. The properties of consolidated wood are examined, especially with respect to the degradation of the wood post-conservation. Different consolidants are reviewed along with their use and properties. The merits and risks of reburial and in situ preservation are considered as an alternative to conservation.

Grafting of (3-Chloropropyl)-Trimethoxy Silane on Halloysite Nanotubes Surface

Modified halloysite nanotubes (HNTs-Cl) were synthesized by a coupling reaction with (3-chloropropyl) trimethoxysilane (CPTMS). The incorporation of chloro-silane onto HNTs surface creates HNTs-Cl, which has great chemical activity and is considered a good candidate as an active site that reacts with other active molecules in order to create new materials with great applications in chemical engineering and nanotechnology. The value of this work lies in the fact that improving the degree of grafting of chloro-silane onto the HNT’s surface has been accomplished by incorporation of HNTs with CPTMS under different experimental conditions. Many parameters, such as the dispersing media, the molar ratio of HNTs/CPTMS/H2O, refluxing time, and the type of catalyst were studied. The greatest degree of grafting was accomplished by using toluene as a medium for the grafting process, with a molar ratio of HNTs/CPTMS/H2O of 1:1:3, and a refluxing time of 4 h. The addition of 7.169 mmol of triethylamine (Et3N) and 25.97 mmol of ammonium hydroxide (NH4OH) led to an increase in the degree of grafting of CPTMS onto the HNT’s surface.

Understanding the Effects of Crosslinking and Reinforcement Agents on the Performance and Durability of Biopolymer Films for Cultural Heritage Protection

In the last two decades, the naturally occurring polysaccharides, such as chitosan and pectin, have gained great attention having potential applications in different sectors, from biomedical to new generation packaging. Currently, the chitosan and pectic have been proposed as suitable materials also for the formulation of films and coatings for cultural heritage protection, as well as packaging films. Therefore, the formulation of biopolymer films, considering only naturally occurring polymers and additives, is a current challenging trend. This work reports on the formulation of chitosan (CS), pectin (PC), and chitosan:pectin (CS:PC) films, also containing natural crosslinking and reinforcement agents, such as citric acid (CA) and halloysite nanotubes (HNT), through the solvent casting technique. The produced films are characterized through water contact angle measurements, infrared and UV–visible spectroscopy and tensile test, while the durability of the CS:PC films is evaluated subjecting the film to accelerated UVB exposure and monitoring the photo-oxidation degradation in time though infrared spectroscopy. All obtained results suggest that both crosslinking and reinforcement agents have beneficial effects on the wettability, rigidity, and photo-oxidation resistance of biopolymer films. Therefore, these biopolymer films, also containing naturally occurring additives, have good properties and performance and they are suitable as coverage films for cultural heritage protection.

Drying Stress and Strain of Wood: A Review

Wood drying stress causes various drying defects, which result from the wood microstructure and the transfer of heat and mass during the drying. It is the fundamental way to solve the problem of defects to clarify the law and mechanism of wood stress and strain development during drying. In this paper, based on the defects of wood drying, the theory and experimental testing methods of drying stress and strain were summarized. Meanwhile, artificial neural networks (ANN) and their application in the wood drying field were also investigated. The traditional prong and slicing methods were used practically in the research and industry of wood drying, but the stress changes in-process cannot be trapped. The technologies of image analysis and near-infrared spectroscopy provide a new opportunity for the detection of drying stress and strain. Hence, future interest should be attached to the combination of the theory of heat and mass transfer and their coupling during drying with the theory of microscopic cell wall mechanics and macroscopic drying. A more complete image acquisition and analysis system should be developed to realize the real-time monitoring of drying strain and cracking, practically. A more feasible and reasonable prediction model of wood drying stress and strain should be established to achieve the accuracy of the prediction.

Halloysite Nanotubes with Immobilized Plasmonic Nanoparticles for Biophotonic Applications

Halloysite nanotubes (HNTs) with immobilized gold (Au) and silver (Ag) nanoparticles (NPs) belong to a class of nanocomposite materials whose physical properties and applications depend on the geometry of arrangements of the plasmonic nanoparticles on HNT’ surfaces. We explore HNTs:(Au, Ag)-NPs as potential nano-templates for surface-enhanced Raman scattering (SERS). The structure and plasmonic properties of nanocomposites based on HNTs and Au- and Ag-NPs are studied by means of the transmission electron microscopy and optical spectroscopy. The optical extinction spectra of aqueous suspensions of HNTs:(Au, Ag)-NPs and spatial distributions of the electric fields are simulated, and the simulation results demonstrate the corresponding localized plasmonic resonances and numerous “hot spots” of the electric field nearby those NPs. In vitro experiments reveal an enhancement of the protein SERS in fibroblast cells with added HNTs:Ag-NPs. The observed optical properties and SERS activity of the nanocomposites based on HNTs and plasmonic NPs are promising for their applications in biosensorics and biophotonics.

Effect of Surfactant Molecular Structure on Emulsion Stability Investigated by Interfacial Dilatational Rheology

Polyglycerol polyricinolate (PGPR) and polyglycerol-2 dioleate were selected as model surfactants to construct water-in-oil (W/O) emulsions, and the effect of interfacial rheological properties of surfactant film on the stability of emulsions were investigated based on the interfacial dilatational rheological method. The hydrophobicity chain of PGPR is polyricinic acid condensed from ricinic acid, and that of polyglycerol-2 dioleate is oleic acid. Their dynamic interfacial tensions in 15 cycles of interfacial compression-expansion were determined. The interfacial dilatational viscoelasticity was analyzed by amplitude scanning in the range of 1–28% amplitude and frequency sweep in the range of 5–45 mHz under 2% amplitude. It was found that PGPR could quickly reach adsorption equilibrium and form interfacial film with higher interfacial dilatational viscoelastic modulus to resist the deformation of interfacial film caused by emulsion coalescence, due to its branched chain structure and longer hydrophobic chain, and the emulsion thus presented good stability. However, polyglycerol-2 dioleate with a straight chain structure had lower interfacial tension, and it failed to resist the interfacial disturbance caused by coalescence because of its lower interfacial dilatational viscoelastic modulus, and thus the emulsion was unstable. This study reveals profound understanding of the influence of branched structure of PGPR hydrophobic chain on the interfacial film properties and the emulsion stability, providing experimental reference and theoretical guidance for future design or improvement of surfactant.

Restoration of a XVII Century’s predella reliquary: From Physico-Chemical Characterization to the Conservation Process

We report on the restoration of a XVII century’s predella reliquary, which is a part of a larger setup that includes a wall reliquary and a wooden crucified Christ, both belonging to the church of “Madre Maria SS. Assunta”, in Polizzi Generosa, Sicily, Italy. The historical/artistic and paleographic research was flanked successfully by the scientific objective characterization of the materials. The scientific approach was relevant in the definition of the steps for the restoration of the artefact. The optical microscopy was used for the identification of the wood species. Electron microscopy and elemental mapping by energy-dispersive X-ray (EDX) was successful in the identification of the layered structure for the gilded surface. The hyperspectral imaging method was successfully employed for an objective chemical mapping of the surface composition. We proved that the scientific approach is necessary for a critical and objective evaluation of the conservation state and it is a necessary step toward awareness of the historical, liturgical, spiritual and artistic value. In the second part of this work, we briefly describe the conservation protocol and the use of a weak nanocomposite glue. In particular, a sustainable approach was considered and therefore mixtures of a biopolymer from natural resources, such as funori from algae, and naturally occurring halloysite nanotubes were considered. Tensile tests provided the best composition for this green nanocomposite glue.

Assessment of Mechanical Properties and Structural Morphology of Alkali-Activated Mortars with Industrial Waste Materials

Alkali-activated products composed of industrial waste materials have shown promising environmentally friendly features with appropriate strength and durability. This study explores the mechanical properties and structural morphology of ternary blended alkali-activated mortars composed of industrial waste materials, including fly ash (FA), palm oil fly ash (POFA), waste ceramic powder (WCP), and granulated blast-furnace slag (GBFS). The effect on the mechanical properties of the Al2O3, SiO2, and CaO content of each binder is investigated in 42 engineered alkali-activated mixes (AAMs). The AAMs structural morphology is first explored with the aid of X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy measurements. Furthermore, three different algorithms are used to predict the AAMs mechanical properties. Both an optimized artificial neural network (ANN) combined with a metaheuristic Krill Herd algorithm (KHA-ANN) and an ANN-combined genetic algorithm (GA-ANN) are developed and compared with a multiple linear regression (MLR) model. The structural morphology tests confirm that the high GBFS volume in AAMs results in a high volume of hydration products and significantly improves the final mechanical properties. However, increasing POFA and WCP percentage in AAMs manifests in the rise of unreacted silicate and reduces C-S-H products that negatively affect the observed mechanical properties. Meanwhile, the mechanical features in AAMs with high-volume FA are significantly dependent on the GBFS percentage in the binder mass. It is also shown that the proposed KHA-ANN model offers satisfactory results of mechanical property predictions for AAMs, with higher accuracy than the GA-ANN or MLR methods. The final weight and bias values given by the model suggest that the KHA-ANN method can be efficiently used to design AAMs with targeted mechanical features and desired amounts of waste consumption.