A useful piece of patent law to know: if a technical description in a public forum is sufficient to enable a person skilled in the art to practice the method, meaning someone could read it and make the thing work, it becomes prior art. In the United States, the disclosing party has a one-year grace period to file their own application. After that, the disclosure precludes anyone else from patenting the same method. Public description is a legal instrument, not just a post.
With that in mind, here's where I think the trace-detection work on lead using methylammonium bromide should go next.
Wang et al. (2021) demonstrated that trace detection was feasible at low lead concentrations. Their method adhered a sulfur compound to alumina, then used it to extract lead from a 5 ppb solution in water. Across the run they accumulated approximately 0.25 micrograms of lead, which produced a visible green glow under UV. The alumina was two-sided, meaning roughly half the emitted fluorescence was radiated away from the observer, and the target area was larger than a square centimeter.
My own work on lead-based-paint particles has shown that a single particle about 40 micrometers across can glow visibly under the same chemistry. The particle does not need to be large. That points to the next move: shrink the target.
A small, dense, one-sided target concentrates the signal. The chemicals used in Wang's method work as-is on the modified surface. Practically, I have had success functionalizing the surface of alumina and silica powder (60-angstrom pore size, 400 mesh), using kapton tape as a resist on ordinary glass, cutting small circles in the resist with a fiber laser (0.1 mm), applying crazy glue, UV-cured resin, or heat-cured resin to the exposed glass, then dusting the alumina or silica powder onto the bare substrate before peeling the resist.
The result is a small target that captures a lot of lead for its size. The sample solution is then passed over the dot, using a tesla valve to recirculate the solution multiple times through a single inlet, or a flow-metered injection infusion setup positioned close to the dot for maximum contact.
Under UV, perovskite crystals of methylammonium lead bromide formed at the target are an efficient way to find very small amounts of lead. Even a 100-nanogram dust particle smeared across half an inch reads as a visible line.
This post is intended to document where the work is, for the record. The method sketch above is publicly disclosed.
That's what the rest of this book is going to be about.
You can catch it with a flashlight and spray bottle in your hands.
Test your stuff. Move on.
Glow-based primary lead detection, direct from the manufacturer.
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