Generate several questions and corresponding answers for each sentence：
Sensors are used in diverse industries and firms for military, health care, food processing as well as agriculture for several applications in a recent industrial landscape. The device that enhances the detection and transformation of a substance's quantifiable chemical, biological and physical qualities into human-readable signals are referred to as sensors. Ever since the discovery of nanosensors that operate on a nanoscale (10–9 m), the use of traditional sensors has been limited due to the hypersensitivity of this nanoscale device. Carbon quantum dots (CQD) are a fast-metamorphosing new class of zero-dimensional carbon-based nanosystem (<10 nm) that has recently grown popular due to its outstanding sensing properties and has become of great importance after graphene, carbon materials, and carbon nanotubes. CQD have been reportedly observed to have the combined advantage of high conductivity, low purchasing cost, easy surface modification, high stability, low toxicity, and tunable photoluminescence (PL). 

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