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Microorganisms, including fungi, bacteria, cyanobacteria, and algae, frequently colonize the surfaces of cultural heritage materials. These biological agents can cause biodeterioration through various mechanisms, resulting in aesthetic alteration, physical disruption, or compromise of mechanical integrity. To assess the presence and diversity of microorganisms, a combination of microscopy techniques is commonly used in conjunction with results from both culture-dependent and culture-independent methods. However, microbial populations are often underestimated. To address this issue, microorganisms can be detected by their intrinsic fluorescence, which can be observed via fluorescence microscopy. This approach facilitates the mapping of the spatial arrangement of microorganisms and the understanding of colonization patterns, thereby complementing established imaging techniques and providing insight into the interactions of microbial communities with the substrate. Given the limited research in this area, we examine the potential of microorganism autofluorescence as a molecular tool for investigating biodeterioration in artistic and architectural heritage, with a particular focus on paper and stone materials. Identifying and understanding the diverse microbiota that may be present is crucial for developing tailored and effective preventive measures and conservation treatments, as some of the species discovered may pose significant risks to both artifacts and human health., (© 2024 Wiley-VCH GmbH.)

The correlation of mechanical properties of polymer materials with those of their molecular constituents is the foundation for their holistic comprehension and eventually for improved material designs and syntheses. Over the last decade, optical force probes (OFPs) were developed, shedding light on various unique mechanical behaviors of materials. The properties of polymers are diverse, ranging from soft hydrogels to ultra-tough composites, from purely elastic rubbers to viscous colloidal solutions, and from transparent glasses to super black dyed coatings. Only very recently, researchers started to develop tailored OFP solutions that account for such material requirements in energy (both light and force), in time, and in their spatially detectable resolution. We here highlight notable recent examples and identify future challenges in this emergent field., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Invited for the cover of this issue are Robert Göstl and co-workers at DWI-Leibniz Institute for Interactive Materials, RWTH Aachen University and Heidelberg University. The image depicts the tailoring of optical force probes for analyzing polymer materials. Read the full text of the article at 10.1002/chem.202102938., (© 2021 Wiley-VCH GmbH.)

The fracture of polymer materials is a multiscale process starting with the scission of a single molecular bond advancing to a site of failure within the bulk. Quantifying the bonds broken during this process remains a big challenge yet would help to understand the distribution and dissipation of macroscopic mechanical energy. We here show the design and synthesis of fluorogenic molecular optical force probes (mechanofluorophores) covering the entire visible spectrum in both absorption and emission. Their dual fluorescent character allows to track non-broken and broken bonds in dissolved and bulk polymers by fluorescence spectroscopy and microscopy. Importantly, we develop an approach to determine the absolute number and relative fraction of intact and cleaved bonds with high local resolution. We anticipate that our mechanofluorophores in combination with our quantification methodology will allow to quantitatively describe fracture processes in materials ranging from soft hydrogels to high-performance polymers., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Invited for this month's cover is the group of Dr. Robert Göstl at DWI - Leibniz Institute for Interactive Materials, Germany. The cover shows the mechanochemically induced retro Diels-Alder reaction of the adduct of a π-extended anthracene and maleimide yielding highly fluorescent anthracenes. This mechanophore motif as well as other force-responsive molecules are reviewed with regard to their efficient activation and quantification. Read the full text of the Minireview at 10.1002/cplu.201900737., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In recent years, polymer mechanochemistry has evolved as a methodology to provide insights into the action-reaction relationships of polymers and polymer-based materials and composites in terms of macroscopic force application (stress) and subsequent deformation (strain) through a mechanophore-assisted coupling of mechanical and chemical phenomena. The perplexity of the process, however, from the viewpoint of mechanophore activation via a molecular-scaled disruption of the structure that yields a macroscopically detectable optical signal, renders this otherwise rapidly evolving field challenging. Motivated by this, we highlight here recent advancements of polymer mechanochemistry with particular focus on the establishment of methodologies for the efficient activation and quantification of mechanophores and anticipate to aptly pinpoint unresolved matters and limitations of the respective approaches, thus highlighting possible developments., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)