Month: April 2018

Warning: Graphite oxide explosions

Graphite oxide (GO; also known as graphene oxide) is an intermediate compound used in its own right and as a route to graphene. Several papers over the last few years have indicated that bulk GO, when heated, can explode; samples of a few milligrams created energy releases that damaged laboratory equipment. (Qiu, Y., et.al. Explosive thermal reduction of graphene-oxide based materials: Mechanism and safety implications. Carbon 72, 2014, pp215-223. Doi: https://doi.org/10.1016/j.carbon.2014.02.005)

Self-heating is also possible, particularly with addition of dopants such as hydroxyl ions (-OH), which drop the temperature for thermal runaway by as much as 50˚C. Such a reduction can overlap with common processing temperatures for GO.

Results presented at the recent American Chemical Society meeting in New Orleans (Green, M.J., et.al. Study of safer storage of graphene oxide. Paper number CHAS 3.) indicate that the temperature at which thermal runaway/explosion occurs drops as the amount of material increases due to mass and thermal transfer effects.

Storage of substantial quantities of GO therefore may pose both a laboratory and a process hazard. It is recommended that researchers working with this material minimize storage, perform a thorough literature search before heating GO, and take appropriate precautions to protect against mishaps.

Warning: Laser eye protection for ultrafast lasers may not be protective

Laser eye protection is normally rated using continuous-wave, narrow-bandwidth lasers. Nevertheless, some labs use pulsed lasers, which have wider bandwidths and higher peak powers; in the case of pico- and femtosecond pulses, this is taken to extremes.

Recent work at NIST and Hood College in Frederick, MD, has shown that much laser protective eyewear is not capable of withstanding fast laser pulses. (J. Laser Appl. 2017, DOI: 10.2351/1.5004090) 22 different pairs of eye protection were tested against a 40-80 fs pulsed laser, and more than half failed to perform as rated. All plastic protective lenses failed.

It is strongly recommended that when selecting laser protective eyewear, you test the eyewear against your particular use condition to ensure that they provide adequate protection. The Laser Safety Advocate, Niel Leon, is available to assist with testing of this sort.

Further information can be found in the cited paper and in this article in Chemical & Engineering News.

Hazard assessment resources from the ACS

Hazard assessment is an important part of the overall process of controlling hazards in the laboratory. The American Chemical Society recently developed a website that gives detailed information and tools for doing hazard assessments–tools that apply not only to chemistry but to all laboratory research.

I encourage all researchers to look at the ACS’s site to see what lessons can be learned. If you would like an introduction to the resources available or a “teach-in” on a particular part (e.g., standard operating procedures–what we call “experimental protocols” in academia), please contact me at [email protected].

Warning: Azidophenylalanine

The unnatural amino acid azidophenylalanine is used for modifying and labeling proteins in biological and biochemical research. The azido group, though, is often a bad actor, leading to “energetic events,” (i.e., explosions).

A recent article in J. Org. Chem. (doi:10.1021/acs.joc.8b00270) by Mark Richardson, Gregory Weiss, and other University of California researchers describes an inexpensive synthesis of this amino acid. In the course of the research, the researchers studied the intermediates and final product using differential scanning calorimetry and discovered that azidophenylalanine “behaved like an explosive compound,” an unexpected result. The authors recommend that crystalline samples of azidophenylalanine not be stored for long periods and that all stocks of the material be kept in dilute aqueous solution.

Further details can be found in a Safety Note in Chemical & Engineering News.