Rising Like a Phoenix from the Ashes: Fire‐Proof Magnetically Retrievable Supraparticles with an Optical Fingerprint for Postmortem Identification of Products

Abstract

correctly and rarely meet the required safety standards. [1,2] Frequently, counterfeit components cause a short circuit, overheat, and subsequently catch fire. Manufacturers are liable in such a scenario and face an enormous reputational loss unless they can prove forgery. This topic is highly relevant for forward-looking industries such as electromobility and automatization, since counterfeit battery cells, for example, can result in vehicle fires.Fire-proof postmortem labels could, for example, enable publicly appointed and sworn experts to verify the originality of a product even after a fire. To our knowledge, however, there are currently no suitable marking technologies available to prove beyond doubt the originality of an object after a fire.In forensic science, comprehensive analytical methods have been applied and further developed to characterize fire debris. Examples include gas chromatography coupled with a mass spectrometry detector, [3][4][5] isotopic ratio mass spectrometry, [6,7] capillary electrophoresis, [8][9][10] or vibrational spectroscopic analysis methods, such as Raman or infrared spectroscopy. [11][12][13] All established methods for the characterization of fire residues have in common that they are complicated, as well as time-and cost-intensive, since also partly complex extraction steps of the analyte are necessary. Moreover, they are based exclusively on the analysis of the intrinsic material properties of burned objects, which, however, can change considerably and manifold depending on the fire condition. [14] Conventional anticounterfeiting features, such as miniaturized printed watermarks or quick response (QR) codes, as well as radio-frequency Identification (RFID) chips, show a sufficient performance during the useful life of a product but are unsuitable for postmortem identification as they are to a large extent not fire-proof. There have been attempts to coat RFID chips with anti-fire materials to increase their resistance when exposed to fire. However, tests were successful only up to 250 °C and the tags are limited in that their components decompose thermally above temperatures beyond ≈500 °C. [15] In addition, these tags are in the macroscopic size range and are not suitable for marking components of electronic devices (e.g., microchips).For these reasons, novel approaches are needed to verify the originality of burned electronic devices. Within the last Counterfeit electronic products not only cause financial losses but also come with safety risks. The worst-case failure scenario certainly is a fire event. Since manufacturers are liable for damages and suffer image loss, fire-proof postmortem taggants are needed, enabling differentiation between originals and counterfeits even after a fire incident. This work presents such taggants: optomagnetic supraparticles (SPs), i.e., complex microscale particles composed of luminescent and magnetic nanoparticles (NPs) are generated. Their hybrid nature is pivotal, as magnetic separation can effectively remove the tags from light-absorb...

Multifunctional, Hybrid Materials Design via Spray‐Drying: Much more than Just Drying

“…These building blocks might be very different, for instance, to enable an optical or magnetic ID, nano and molecular moieties such as organic dyes, lanthanides, MOFs, quantum dots, nanosilica, nano-polymer-particles, nano-iron-oxides, and many more are employed. [6,7,21,137,148] Often, the ID is based on ratiometric and spectral pattern principles that can be designed via a flexible choice of building block combinations and ratios. [6,148,153] This flexibility in choice is key and can only be guaranteed if the process of joining the building blocks comes without too many restrictions, i.e., this is another example where spray-drying is superior compared to many other techniques.…”

“…The self-assembly of building blocks, such as nanoparticles and molecules within a single droplet upon solvent evaporation [8,15] can produce a variety of compositions (e.g., single-component, [16] multi-component, [17,18] inorganic-organic hybrid, [19] metal oxide hybrid [20,21] ) and structures (e.g., solid, [22] hollow, [23] core-shell [23] ) with unique properties and potential applications. Recently, many types of unique building blocks such as nanofibers, [24] nanorods, [25] and metal-organic frameworks (MOFs) [26,27] have become available and offer potential advantages.…”

Communicating Supraparticles to Enable Perceptual, Information‐Providing Matter

“…Alternatively, the distribution of signal carriers can be altered by the addition of nonsignal-carrying, environmentally robust, NPs, e.g., SiO 2 NPs, and their utilization as spacers (Figure 5a4). [54,114,170,171] Such an architecture reduces the interplay between interacting species by increasing their distances. Another strategy to reduce the interaction of all signal-carrying building blocks is the encapsulation of individual or soft-agglomerated signal carrier types into, for instance, polymer NPs and their subsequent assembly into multihierarchical SP architectures (Figure 5a5).…”

“…Pioneering examples include the creation of SP-based coatings via doctor blade coating, [145,146,156,167,168,186] spray-coating, [187] or low-tech alternatives using acrylate- [188] or polysilazane-based lacquers. [151,171] Such SP coatings could be suitable for CSPS with an optical communication pathway and allow optically transmitted information to be detected if transparent coating materials are used. [151,156,167,168] Other studies showed that magnetic SPs can be embedded into agar, [189] adhesives, [54] or polymers via melt-blending.…”

Magnetic Supraparticles Capable of Recording High‐Temperature Events

“…[7,8] Yet, it was found that the favorable superparamagnetic properties can be conserved even after temperature exposure up to 1000 °C via embedment of SPIONs into silica (SiO 2 ) matrices. [8][9][10][11][12][13][14] Herein, we demonstrate a way how to exploit the vulnerability toward oxidation and the consequent loss of (strong) magnetic properties on the one hand and the protectability of the magnetic properties using silica on the other hand in a combined system in order to achieve a functional magnetic system, namely a magnetic high-temperature recorder (See Supporting Information for the definition of "recorder" in this context). To do so, SPIONs with and without silica protection, respectively, are combined as two distinct building blocks in a so-called supraparticle (SP) via forced assembly using spray-drying.…”