Table 1.

The difference between a graphene-based electrical sensor and a graphene-based optical sensor.

	Work Principle	Advantages	Disadvantages	References
Graphene electrical sensor	Since graphene exhibits ambipolar behavior, the p-type or n-type behavior can be tuned effectively by the gate voltage. The principle of sensing is based on changes in drain-source conductivity of the graphene channel upon the binding of the sample to the receptor-functionalized graphene.	Small size, large surface area, fast electron transfer, fast response time, high sensitivity, and reduced surface contamination	Only measure current changes, low spatial resolution, damage samples, affect results	Ang et al. 2011 [63]
Graphene optical sensor	Under total internal reflection, graphene exhibits characteristics of enhanced polarization absorption and broadband absorption. The sensor uses the attenuated total reflection method to detect the refractive index change near the sensor surface.	High spatial resolution, wide and deep detection range, high sensitivity and high precision, accurate and fast detection, unlabeled samples	Since the light absorption rate of single-layer graphene is too low, the area generated by the active photocurrent is too small. Aggregation and precipitation of high concentration samples may affect optical detection.	Wu et al. 2010 [68]