Lanthanide-doped upconversion nanoparticles (UCNPs) are capable of converting near-infra-red excitation into visible and ultraviolet emission. Their unique optical properties have advanced a broad range of applications, such as fluorescent microscopy, deep-tissue bioimaging, nanomedicine, optogenetics, security labelling and volumetric display. However, the constraint of concentration quenching on upconversion luminescence has hampered the nanoscience community to develop bright UCNPs with a large number of dopants. This review surveys recent advances in developing highly doped UCNPs, highlights the strategies that bypass the concentration quenching effect, and discusses new optical properties as well as emerging applications enabled by these nanoparticles.

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by 2023 the global anticounterfeiting packaging market is projected to reach 208.4 billion USD. [9] The field of anticounterfeiting has a moving target. Initially, for example, almost every country implemented watermarks or fluorescence labels on banknotes to deter copying. [1] Nowadays, a broad range of optical nanomaterials, including metallic nanoparticles, organic dyes, semiconducting quantum dots, and lanthanide-doped nanoparticles (Figure 1) are available to be explored for developing next-generation anticounterfeiting technologies. Thanks to the rapid development of material science, wet-chemistry methods are available for highly controllable synthesis, allowing a large range of nanoparticles with distinguished optical features to be employed as anticounterfeiting taggants. Among them, lanthanide-doped upconversion nanoparticles (UCNPs) are outstanding for the feasibility to tune their optical properties in multiple dimensions. Here, we survey the recent progress in anticounterfeiting applications using new collections of optical nanomaterials as security inks and point out that UCNPs are one of the most promising candidates for high-security-level anticounterfeiting applications. [10] Moreover, we present an outlook for future trends in encryption and decryption devices and technologies toward their real-world adoptions. Nanoparticles for Anticounterfeiting ApplicationsGenerally, anticounterfeiting is done by verifying authentic information that can be either covert or overt. In a typical decoding process, the retrieved information may manifest itself as fluorescence color and intensity in patterns that are varying in the time and space domains. As a crucial element of anticounterfeiting technology, an encoding material serves as a carrier of distinct authentic information. [15] Hence, to achieve a high anticounterfeiting level, the encoding material should be able to offer abundant optical states that can be tailored to carry unique information. In this regard, nanoparticle materials (Table 1) have attracted tremendous interest owing to their exceptional stability, controllability, and diversity in tuning their optical properties in multiple dimensions, e.g., fluorescence color, intensity, and lifetime value. We surveyed and summarized several key fundamental optical features including reflection, absorption, scattering, and fluorescence that can be Optical nanomaterials have been widely used in anticounterfeiting applications. There have been significant developments powered by recent advances in material science, printing technologies, and the availability of smartphone-based decoding technology. Recent progress in this field is surveyed, including the availability of optical reflection, absorption, scattering, and luminescent nanoparticles. It is demonstrated that advances in the design and synthesis of lanthanide-doped upconversion nanoparticles will lead to the next generation of anticounterfeiting technologies. Their tunable optical properties and optical responses to a range of external stimuli a...

Recombination of rapidly evolving RNA-viruses provides an important mechanism for diversification, spread, and emergence of new variants with enhanced fitness. Foot-and-mouth disease virus (FMDV) causes an important transboundary disease of livestock that is endemic to most countries in Asia and Africa. Maintenance and spread of FMDV are driven by periods of dominance of specific viral lineages. Current understanding of the molecular epidemiology of FMDV lineages is generally based on the phylogenetic relationship of the capsid-encoding genes, with less attention to the process of recombination and evolution of non-structural proteins. In this study, the putative recombination breakpoints of FMDVs endemic to Southeast Asia were determined using full-open reading frame sequences. Subsequently, the lineages' divergence times of recombination-free genome regions were estimated. These analyses revealed a close relationship between two of the earliest endemic viral lineages that appear unrelated when only considering the phylogeny of their capsid proteins. Contrastingly, one lineage, named O/CATHAY, known for having a particular host predilection (pigs) has evolved independently. Additionally, intra-lineage recombination occurred at different breakpoints compared to the inter-lineage process. These results provide new insights about FMDV recombination patterns and the evolutionary interdependence of FMDV serotypes and lineages. Foot-and-mouth disease (FMD) is one of the most important diseases of livestock worldwide 1,2. Many countries with endemic FMD have rural populations that are highly reliant on their livestock as critical assets. The causal agent, FMD virus (FMDV), affects cloven-hoofed animals and is endemic in all countries in mainland Southeast Asia, where clinical cases are regularly observed in livestock, including pigs, cattle, Asian buffalo and small ruminants. FMDV belongs to the genus Aphthovirus of the family Picornaviridae and has a single-stranded, positive-sense, non-segmented RNA genome consisting of an open reading frame (ORF) region of ~7000 nucleotides (nt). The genome encodes for a single polyprotein that is post-translationally processed into 4 capsid proteins (VP1-4) and 10 non-structural proteins (NSP; leader proteinase (L pro), 2A, 2B, 2C, 3A, 3B1 VPg1 , 3B2 VPg2 , 3B3 VPg3 , 3C pro and 3D pol), bounded by 5′and 3′untranslated regions (UTRs) 3. FMDV has been classified into seven distinct serotypes, namely A, O, C, Asia-1, Southern African Territories (SAT) 1, SAT 2 and SAT 3 4 , many of which exist as multiple strains or lineages circulating in endemic regions 5 .

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