Question

how can you tell that this example is open or paywalled?
advanced photonics research
open access
review open access
apparent colors of 2d materials
sergio pueblo hai li, hua zhang, andres castellanos gomez
first published: 05 january 2022 | https://doi.org/10.1002/adpr.202100221
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abstract
finding 2d and thin-film layered materials have become essential to develop not only in
scientific-related fields, but also in a wide industry, which is constantly feeding from this
progress. for electronic devices, thin-film materials are supposed to be a step forward to
overcome moore’s law. in many other technologic areas, the development of tools based
on flakes of materials has found new physics, becoming a rising field. although,
destructive techniques are commonly used to characterize the thickness of these
materials, herein, a list of materials is presented, whose thicknesses are characterized by
their apparent colors in several substrates, a harmless, fast, and reliable technique that
has been already used to determine the number of layers in several works. this list is
also enlarged with other materials and substrates.

Explanation:

To determine if the example is open or paywalled, we look for indicators. The journal title "ADVANCED PHOTONICS RESEARCH" has an "Open Access" label. Also, there's an "Open Access" tag next to the "Review" label. These visual cues (the "Open Access" text) show it's open - access (not paywalled), as open - access publications explicitly label themselves as such to indicate free availability.

Answer:

This example is open (not paywalled) because the journal "ADVANCED PHOTONICS RESEARCH" has an "Open Access" label, and there is also an "Open Access" tag next to the "Review" label, indicating it is an open - access publication.