A novel colorimetric nanosensor is reported for the selective and sensitive determination of cysteine using magnetic-sulfur, nitrogen graphene quantum dots (Fe₃O₄/S, N-GQDs), and gold nanoparticles (Au NPs). Thus, S, N-GQDs was firstly immobilized on Fe₃O₄ nanoparticles through its magnetization in the presence of Fe³⁺ in the alkali solution. The prepared Fe₃O₄/S, N-GQDs were dispersed in cysteine solution resulting in its quick adsorption on the surface of the Fe₃O₄/S, N-GQDs through hydrogen bonding interaction. Then, Au NPs solution was added to this mixture that after a short time, the color of Au NPs changed from red to blue, the intensity of surface plasmon resonance peak of Au NPs at 530 nm decreased, and a new peak at a higher wavelength of 680 nm appeared. The effective parameters on cysteine quantification were optimized via response surface methodology using the central composite design. Under optimum conditions, the absorbance ratio (A₆₈₀/A₅₃₀) has a linear proportionality with cysteine concentration in the range of 0.04–1.20 μmol L⁻¹ with a limit of detection of 0.009 μmol L⁻¹. The fabrication of the reported nanosensor is simple, fast, and is capable of efficient quantification of ultra traces of cysteine in human serum and urine real samples.

报道了一种新型比色纳米传感器，用于使用磁硫，氮石墨烯量子点（Fe ₃ O ₄ / S，N-GQDs）和金纳米颗粒（Au NPs）选择性和灵敏地测定半胱氨酸。因此，首先，在碱溶液中存在Fe ^3+时，通过磁化将S，N-GQDs固定在Fe ₃ O ₄纳米颗粒上。将制备的Fe ₃ O ₄ / S，N-GQDs分散在半胱氨酸溶液中，使其快速吸附在Fe ₃ O ₄的表面上/ S，N-GQDs通过氢键相互作用。然后，向该混合物中添加Au NPs溶液，短时间内，Au NPs的颜色从红色变为蓝色，Au NPs在530 nm处的表面等离振子共振峰的强度降低，而在较高波长处出现新的峰出现680nm的波长。使用中央复合设计，通过响应面方法优化了半胱氨酸定量的有效参数。在最佳条件下，吸光度比（A ₆₈₀ / A ₅₃₀）与半胱氨酸浓度在0.04-1.20μmolL ^-1范围内成线性比例，检出限为0.009μmolL ^-1。所报道的纳米传感器的制造简单，快速，并且能够有效地定量人血清和尿液实际样品中的半胱氨酸超痕量。