Supramolecular nanoparticle hybrids for biosensing of analytes have been a major focus due to their tunable optical and surface properties. Quantum dots-Gold nanoparticle (QDs-GNP) based FRET probes involving turn on/off principles have gained immense interest due to their specificity and sensitivity. Recent focus is on applying these supramolecular hybrids for enzyme operated biosensors that can specifically turn-on fluorescence induced by co-factor or product formed from enzymatic reaction. The present study focuses on locking and unlocking the interaction between QD-GNP pair leading to differential fluorescent properties. Cationic GNPs efficiently quenched the anionic QD fluorescence by forming nanoparticle hybrid. Quenching interaction between QD-GNP pair was unlocked by NADH leading to QD fluorescence turn-on. This phenomenon was applied for the successful detection of formaldehyde using NAD⁺ dependent formaldehyde dehydrogenase. The proposed nano-sniffer could successfully detect formaldehyde from 0.001 to 100000 ng/mL (R² = 0.9339) by the turn off-turn on principle. It could also detect formaldehyde in fruit juice and wine samples indicating its stability and sensitivity in real samples. The proposed nanoprobe can have wide applications in developing enzyme biosensors in future.

由于其可调节的光学和表面特性，用于分析物生物传感的超分子纳米杂化物已成为主要关注点。基于量子点-金纳米颗粒（QDs-GNP）的涉及开启/关闭原理的FRET探针由于其特异性和敏感性而引起了极大的兴趣。最近的重点是将这些超分子杂交体用于酶操作的生物传感器，该传感器可以特异性地开启由辅因子或由酶促反应形成的产物诱导的荧光。本研究的重点是锁定和解锁QD-GNP对之间的相互作用，从而导致荧光特性差异。阳离子GNP通过形成纳米粒子杂化物有效地猝灭了阴离子QD荧光。NAD释放QD-GNP对之间的猝灭相互作用，导致QD荧光开启。⁺依赖的甲醛脱氢酶。拟议的纳米嗅探器可以通过“关闭-开启”原理成功检测到0.001至100000 ng / mL的甲醛（R ² = 0.9339）。它还可以检测果汁和葡萄酒样品中的甲醛，表明其在真实样品中的稳定性和敏感性。所提出的纳米探针在将来开发酶生物传感器方面可以具有广泛的应用。