The present invention provides materials, devices, and methods related to determination of an analyte. In some embodiments, an analyte may be determined by monitoring, for example, a change in an optical signal of a luminescent material (e.g., particle) upon exposure to an analyte. The present invention may be particularly advantageous in that some embodiments may comprise an emissive species useful as an internal reference standard. Methods of the invention may also be useful in the quantitative determination of an analyte. In some cases, the present invention may allow for selective determination of an analyte.