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The presence of calcareous concretions on the surface of marine archaeological ceramics is a frequently observed phenomenon. It is necessary to remove these materials when the deposits obscure the feature of ceramics. Unfortunately, calcareous concretions provide distinctive documentation of the burning history of ceramics. The interaction of acid solution or detachment of the deposit layers in physical ways leads to the loss of archeological information. To prevent the loss of archeological information and to achieve precise and gentle concretion removal, responsive hydrogel cleaning systems have been developed. The hydrogels synthesized are composed of networks of poly(vinyl acetate)/sodium alginate that exhibit desirable water retention properties, are responsive to Ca2+ ions, and do not leave any residues after undergoing cleaning treatment. Four distinct compositions were selected. The study of water retention properties involved quantifying the weight changes. The composition was obtained from Fourier transform infrared spectra. The microstructure was obtained from scanning electron microscopy. The mechanical properties were obtained from rheological measurements. To demonstrate both the efficiency and working mechanism of the selected hydrogels, a representative study of mocked samples is presented first. After selecting the most appropriate hydrogel composite, a cleaning process was implemented on the marine archaeological ceramics. This article demonstrates the advantages of stimuli-responsive hydrogels in controlling the release of acid solution release, thereby surpassing the limitations of traditional cleaning methods.

Waterlogged archaeological wood samples may degrade during long-term immersion in microbial-activity environments, which causes its biodegradation. Simultaneous dynamic vapor sorption (SDVS) and two-dimensional correlation infrared (2D COS-IR) spectroscopy reveal the degradation inhomogeneity of waterlogged fir wood from the Shengbeiyu shipwreck. The waterlogged and reference wood exhibit type II sorption isotherms. The equilibrium moisture contents of waterlogged archaeological fir wood from a decay region (WFD) were 22.5% higher than those of waterlogged archaeological fir wood from a sound region (WFS). WFD exhibits a higher measurable sorption hysteresis than WFS, implying greater variation in the surface moisture content in the WFD region compared to the WFS region, which may compromise the dimensional stability of the shipwreck. 2D COS-IR spectra confirmed the inhomogeneous degradation of the waterlogged wood via numerous mechanisms. The efficacy of SDVS and 2D COS-IR spectroscopy in the evaluation of the degradation state of waterlogged wood was demonstrated. This study verifies the existence of hygroscopic and chemical differences between visually similar samples from the same shipwreck.

Hygroscopicity is one of the most important properties of wood and plays a decisive role in its dimensional stability. In this context, conservation plans for waterlogged archaeological wood (WAW) and relevant waterlogged artefacts must be created. The size of the sample required for a moisture sorption assessment may affect the results for (and thus the perception of) the hygroscopicity of a testing artefact. Herein, to investigate the effects of the sample size on the hygroscopicity of WAW as measured via dynamic vapour sorption (DVS), typical WAW and recent (i.e., sound) wood are processed into four differently sized samples, ranging in thickness from 200 mesh to millimetre. The equilibrium moisture contents (EMCs) of the wood samples are simultaneously measured using simultaneous DVS. The sorption isotherms show that the EMC values of the recent wood at each relative humidity increase as the sample size decreases, with the superfine powder sample achieving the highest EMC of all of the recent samples. Although the WAW has a higher EMC than that of recent wood, the effect of the size of the WAW sample on its hygroscopic properties is surprisingly not as pronounced as that for the recent wood. In addition, the hysteresis between the samples of different sizes of the archaeological wood is significantly smaller than that for the reference samples. Furthermore, regarding the standard deviations of the parameters obtained from the Guggenheim Anderson de Boer and Hailwood–Horrobin models, the values for WAW are all much smaller than those for the reference wood. This further verifies the disappearance of the size effect of the hygroscopicity for WAW.

Temporary consolidation technique becomes more and more popular in archaeological excavation. Cyclododecane and menthol are the mostly studied and used temporary consolidants. However, their best applying temperatures are about 20-40 °C higher than their melting points, which can be a problem for temperature-sensitive artifacts or excavation in cold environment. In this work, we take advantage of the concept of eutectic mixtures. Menthyl lactate, a menthol derivative, which can also sublime at ambient conditions, is introduced into menthol to form binary eutectic mixtures. Their potentials as temporary consolidants are carefully and systematically examined. The results indicate the eutectic mixtures are good temporary consolidants and their performances at very low temperatures are much better than the parent compounds. Through this work, a list of temporary consolidants whose melting points range from below 0 to 45 °C are built up for conservators to choose based on their needs.

Archaeological wood is a kind of ‘new material’ that has deteriorated due to long-term degradation. The existing wood science theory and evaluation methods are not fully applicable to archaeological wood. Moreover, current physical-mechanical evaluation methods are inadequate for fragile archaeological wood due to their insufficient accuracy and the large sample amount required, causing difficulties in many necessary physical-mechanical repeatability tests. In light of these limitations, the representative samples on Nanhai No. 1, a merchant shipwreck in the Song Dynasty, were selected as the research objects in this paper. The shipwreck is a typical waterlogged wooden artifact. A quasi-nondestructive physical-mechanical evaluation technique for archaeological wood was developed with the thermomechanical analyzer (TMA). This study used TMA to evaluate the bending strength of representative waterlogged archaeological samples of Nanhai No. 1 shipwreck and sound wood with the same species. Besides, the thermal linear expansion coefficients in the ambient temperature range were obtained. The sizes of the samples used in the tests were only 2 mm × 8 mm × 0.3 mm and 1 cm × 1 cm × 1 cm, respectively. Bending strength results of archaeological wood by the TMA method conformed to the tendency that the bending strength decreases with the increase of decay degree. In addition, the longitudinal linear expansion coefficients of archaeological wood reached 80%–115% of those in the transverse grain direction, which were about 10 times higher than those of the sound wood. The linear expansion coefficients of archaeological wood in three directions were similar. Based on the results of Fourier transform infrared analysis (FT-IR), the significant differences in the physical-mechanical properties of the archaeological wood and the sound wood were induced to be mainly ascribed to the decomposition and the loss of hemicellulose in the archaeological wood. The cell wall substrate could not stabilize the cellulose skeleton, which led to the instability of the tracheid structure of the archaeological wood. This study provided a proven quasi-nondestructive method for the preservation state evaluation of waterlogged archaeological wood (WAW) from the Nanhai I shipwreck and other similar waterlogged wooden relics.

Comparing to the research work on the polychromy protection of Qin Shihuang’s Terracotta Army, the protection of the terracotta body itself is somewhat being overlooked. But a very recent survey organized by the State Administration of Cultural Heritage of China shows that the water erosion and salt damage of ancient potteries, including terracotta, are more obvious than previous thoughts. In this work, the protective performances on simulated Qin terracotta samples of two bridged siloxanes with various alkyl bridge groups, bis(triethoxysilyl) ethane and bis(triethoxysilyl) octane, are investigated and compared with tetraethoxysilane and triethoxyoctylsilane. Influences on the porosity and pore size distribution, morphology, physical properties, color alteration and capillary water absorption of untreated and treated terracotta samples are carefully examined. The accelerated freeze-thaw and salt crystallization aging tests are further carried out to evaluate the resistance to aging after protection treatment. The results indicate that both bridged siloxanes show great potential in terracotta consolidation.

Menthol, a natural organic compound from plant extract, due to its unique aromatic smell and cooling effect, has wide applications in food, cosmetic and pharmaceutical industries. By taking advantage of its volatile ability at room temperature, this compound has the potential to be used as a temporary consolidant in the field of art conservation. In order to evaluate the effectiveness of menthol as a temporary consolidant for urgent conservation in archaeological field, in this paper, laboratory investigations, such as menthol's penetration, consolidation efficacy and morphological changes during sublimation, are carried out on two kinds of organic and inorganic materials respectively, representing four types of fragile archaeological artifacts. In particular, the morphological changes of consolidated substrates during menthol sublimation process are systematically observed. The result shows that menthol's consolidation efficacy is strongly affected by the inherent nature of substrate to be treated. Menthol whisker growth on these substrates surfaces is observed, and a weak intermolecular hydrogen bond is formed between menthol and substrate, which is confirmed by the shift of hydroxyl group stretching bond in the IR spectrum.

The photoactivity of semiconductor nanostructures makes them potentially useful for environmental remediation and antibacterial applications. Understanding the mechanism underlying the photochemical and photobiological activities of photoexcited semiconductors is of great importance for developing applications and assessing associated risks. In the current work, using electron spin resonance spectroscopy coupled with spin trapping and spin labeling techniques, we comparatively and systematically investigate the abilities of ZnO and ZnS to generate hydroxyl radical, superoxide, singlet oxygen, photoinduced electrons, and oxygen consumption during irradiation. It was found that although ZnO and ZnS, when photoexcited, can produce hydroxyl radical, superoxide, and singlet oxygen, ZnO is more effective than ZnS in producing hydroxyl radical and singlet oxygen while ZnS is more effective than ZnO in generating superoxide. The characterization with ESR spin labeling and oximetry indicates ZnS is about 4 times m...

Nanostructured enzyme mimics are of great interest as promising alternatives to artificial enzymes for biomedical and catalytic applications. Studying the chemical interactions between antioxidants and nano-enzymes may result in a better understanding of the antioxidant capability of antioxidants and may help improve the function of artificial enzymes to better mimic natural enzymes. In this study, using Co3O4 nanoparticles (NPs) as peroxidase mimics to catalyze the oxidation of chromophoric substrates by H2O2, we developed a platform that acts as a biosensor for hydrogen peroxide and glucose and that can study the inhibitory effects of natural antioxidants on peroxidase mimics. This method can be applied specifically to glucose detection in real samples. Three natural antioxidants, gallic acid (GA), tannic acid (TA), and ascorbic acid (AA), were compared for their antioxidant capabilities. We found that these three antioxidants efficiently inhibit peroxidase-like activity with concentration dependence. The antioxidants showed different efficiencies, in the following order: tannic acid > gallic acid > ascorbic acid. They also showed distinct modes of inhibition based on different interaction mechanisms. This study serves as a proof-of-concept that nano-enzyme mimics can be used to evaluate antioxidant capabilities and to screen enzyme inhibitors.

Identifying the dominantly active species and their reactive behaviors in semiconductor photocatalysis is important for developing a full understanding of their photochemical and photophysical properties. Here we report an effective method for studying the reactive oxygen species (ROS) and charge carriers generated by irradiating single crystalline CdS and Ag2S micro-nano structures (MNS). Our method, based on electron spin resonance spectroscopy (ESR) combined with spin trapping and spin labeling techniques, confirmed the generation of superoxide and charge carriers and their contribution to photocatalytic degradation of rhodamine B elicited by CdS and Ag2S MNS. The electronic band structures determined the reactivity of photogenerated holes/electrons and the generation of reactive oxygen species. Our comparison of CdS and Ag2S MNS showed that, because of the large difference between their band edge positions, these two sulfides differ greatly in ROS production and in the reactivity of photoinduced elect...

Temporary consolidation is widely used to protect delicate artefacts or other fragile relics in art conservation. Although cyclododecane is extensively accepted, the safety-related issues have become an increasing concern and its short working time is always annoying. Inspired by its low melting point, polar structure, well-established safety profile, easy local availability and low cost, we propose menthol as a new temporary consolidant on the new excavation site of Qin Shihuang's Terracotta Army. In this paper, we offer a preliminarily exploration of the kinetics of menthol sublimation on two different matrices, its residue after volatilization, its penetrability and distribution in simulated terracotta samples, as well as other important properties in the laboratory. The results obtained from these tests reveal that the sublimation of menthol can be a zero- or a first-order process, depending on the porosity of the matrices, and its best operational temperature resides in the range of 60–80°C. Finally, two field cases at the archaeological site of Qin Shihuang's Terracotta Army are presented to show that menthol is a very effective temporary consolidant.

Tetraethoxysilane (TEOS) is the most commonly used silicon-based stone consolidant in art conservation. However, it is known that the resulting silica gel phase tends to develop cracks inside the stone as the gel shrinks during aging and drying. Such phenomenon may lead to severe damage to the protected objects. By introducing silica nanoparticles into TEOS, a so-called particle modified consolidant (PMC), may minimize such shrinkage by reducing the volume loss and forming mesoporous structure to weaken the capillary forces. But many previous results show significant color changes on the surface of PMC-treated stones which can not be tolerated in the conservation treatments of cultural heritage. In this work, we designed a three-component composite consolidant which consists of 15 nm silica particles, α,ω-hydroxyl-terminated polydimethylsilane (PDMS-OH) and TEOS. Among the three components, TEOS provides the consolidation function, silica nanoparticles prevent the cracking and increase the salt resistance and PDMS-OH further reduces cracking, decreases the color alteration and increases the resistance to wetting of the stone. Experimental results show that the three components have significant synergistic effect, which makes the material exhibiting best overall performance in terms of cultural heritage protection.

Tuning the enzyme-like activity and studying the interaction between biologically relevant species and nano-enzymes may facilitate the applications of nanostructures in mimicking natural enzymes. In this work, AuPt alloy nanoparticles (NPs) with varying compositions were prepared through a facile method by co-reduction of Au3+ and Pt2+ in aqueous solutions. The composition could be tuned easily by adjusting the molar ratios of added Pt2+ to Au3+. It was found that both peroxidase-like and oxidase-like activity of AuPt alloy NPs were highly dependent on the alloy compositions, which thus suggesting an effective way to tailor their catalytic properties. By investigating the inhibitory effects of HS− on the enzyme-like activity of AuPt alloy NPs and natural enzyme, we have developed a method for colorimetric detection of HS− and evaluation of the inhibiting effects of inhibitors on natural and artificial enzymes. In addition, the responsive ability of this method was influenced largely by the composition: AuPt alloy NPs show much lower limit of detection for HS− than Pt NPs while Pt NPs show wider linear range than AuPt alloy NPs. This study suggests the facile way not only for synthesis of alloy nanostructures, but also for tuning their catalytic activities and for use in bioanalysis.

During excavation, archaeologists always discover very fragile materials which require immediate in situ consolidation before removal to laboratories for conservation treatment. Cyclododecane is on...