*Article* **Portable Instrument for Hemoglobin Determination Using Room-Temperature Phosphorescent Carbon Dots**

**Fabio Murru 1, Francisco J. Romero 2, Roberto Sánchez-Mudarra 2, Francisco J. García Ruiz 2, Diego P. Morales 2,3,4, Luis Fermín Capitán-Vallvey 1,3,4 and Alfonso Salinas-Castillo 1,3,4,\***


Received: 30 March 2020; Accepted: 24 April 2020; Published: 26 April 2020

**Abstract:** A portable reconfigurable platform for hemoglobin determination based on inner filter quenching of room-temperature phosphorescent carbon dots (CDs) in the presence of H2O2 is described. The electronic setup consists of a light-emitting diode (LED) as the carbon dot optical exciter and a photodiode as a light-to-current converter integrated in the same instrument. The reconfigurable feature provides adaptability to use the platform as an analytical probe for CDs coming from di fferent batches with some variations in luminescence characteristics. The variables of the reaction were optimized, such as pH, concentration of reagents, and response time; as well as the variables of the portable device, such as LED voltage, photodiode sensitivity, and adjustment of the measuring range by a reconfigurable electronic system. The portable device allowed the determination of hemoglobin with good sensitivity, with a detection limit of 6.2 nM and range up to 125 nM.

**Keywords:** carbon dots; hemoglobin determination; luminescence; room temperature phosphorescence; portable instrumentation
