Zero-dimensional molybdenum disulfide (MoS₂) quantum dots (QDs) have attracted remarkable interest due to their peculiar properties such as the quantum-confinement effect and high surface area. Exploring recombination dynamics in MoS₂ QDs is not only expected to gain a deeper insight into their fundamental physics, it is also important for potential applications in optoelectronics and energy-conversion technology. This study synthesized p-type MoS₂ QDs doped with diethylenetriamine (DETA) using pulsed laser ablation method. A hole concentration as high as 2.08 × 10¹² cm^–2 has been demonstrated by gate-dependent conductance measurements. A 110-fold enhancement of photoluminescence in the p-type MoS₂ QDs has been found after the introduction of DETA, and the dependence of the radiative and nonradiative recombination of MoS₂ QDs on carrier densities were studied. As the carrier density was increased, a decrease of the radiative lifetime was found, which is similar to the behavior of the radiative lifetime in monolayer MoS₂. The Shockley-Read-Hall (SRH) and Auger recombination dominates the nonradiative recombination at low and high carrier densities, respectively. The SRH lifetime of MoS₂ QDs increases with the increased carrier density, suggesting that the recombination mechanism at the low carrier density is dominated by the SRH recombination. This study found that as the carrier densities exceeded 0.53 × 10¹² cm^–2, the Auger recombination was responsible for the reduction of PL. Furthermore, MoS₂ QDs was used as a fluorescent sensor for the detection of ammonium hydroxide (NH₄OH). The PL intensity of MoS₂ QDs demonstrates a gradual decrease with increasing NH₄OH concentration. By investigating the time-resolved PL (TRPL), the mechanism that leads to the decrease of PL in MoS₂ QDs is addressed. This investigation is expected to demonstrate a promising development of an effective and low-cost MoS₂ QDs-based fluorescent sensor with superior sensitivity for the rapid detection of ammonia in aqueous media.

中文翻译：

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MoS ₂量子点中密度依赖的载流子复合及其对氢氧化铵发光传感的意义

零维二硫化钼（MoS ₂）量子点（QDs）由于其独特的性质（如量子约束效应和高表面积）而引起了人们的极大兴趣。探索MoS ₂ QD中的重组动力学不仅有望对它们的基本物理学有更深入的了解，而且对于光电子学和能量转换技术的潜在应用也很重要。这项研究使用脉冲激光烧蚀方法合成了掺有二亚乙基三胺（DETA）的p型MoS ₂ QD。依赖于栅极的电导测量结果表明，空穴浓度高达2.08×10 ¹² cm ^-2。p型MoS的光致发光增强110倍引入DETA后已发现_2个量子点，并研究了MoS ₂量子点的辐射和非辐射重组对载流子密度的依赖性。随着载流子密度的增加，发现了辐射寿命的降低，这与单层MoS ₂中的辐射寿命的行为相似。在低和高载流子密度下，Shockley-Read-Hall（SRH）和俄歇重组分别占据着非辐射重组的主导地位。MoS ₂ QD的SRH寿命随着载流子密度的增加而增加，这表明低载流子密度下的重组机制受SRH重组的支配。这项研究发现，随着载流子密度超过0.53×10 ¹² cm^–2，俄歇重组导致PL降低。此外，MoS ₂ QDs被用作荧光传感器，用于检测氢氧化铵（NH ₄ OH）。MoS ₂ QD的PL强度随着NH ₄ OH浓度的增加而逐渐降低。通过研究时间分辨的PL（TRPL），解决了导致MoS ₂ QD中PL减少的机制。预期这项研究将显示出一种有效且低成本的基于MoS ₂ QDs的荧光传感器的有前途的发展，该传感器具有出色的灵敏度，可快速检测水性介质中的氨。