Highly luminescent and direct band gap black phosphorus (BP) nanocrystals (NCs) synthesized using a cost‐effective sonochemical exfoliation route are reported. Microscopic studies have confirmed the exfoliation of few‐layer nanoflakes and BP NCs with variable average size between ≈2 and ≈8 nm. Structural and vibrational characteristics reveal the superior crystalline quality by retaining the phase and crystalline symmetry in NCs. Size‐dependent absorption characteristics are observed by controlling the nanoparticle size and show a progressive blue shift near band edge absorption on reducing the size, useful for selective multicolor photodetection. Temperature‐dependent photoluminescence measurements from room temperature (300 K) down to 10 K are performed. Most interestingly, BP NCs with the lowest diameter exhibit a novel negative thermal quenching behavior as compared to positive thermal quenching observed usually in bulk semiconductors and BP NCs with larger diameter. Metal–semiconductor–metal type (Au/BP‐NCs/Au) photodetectors are fabricated to study their photoresponse properties, which reveal the potential application of BP NCs as optical modulators.

中文翻译：

---

高发光磷光纳米晶的负热猝灭和尺寸依赖性光学特性

据报道，采用成本有效的声化学剥落途径合成的高发光和直接带隙黑磷（BP）纳米晶体（NC）。显微镜研究证实了几层纳米薄片和BP NCs的剥落，其平均尺寸在≈2和≈8nm之间变化。通过保留NC中的相和晶体对称性，结构和振动特性显示出优异的晶体质量。通过控制纳米粒子的大小可以观察到与尺寸有关的吸收特性，并且在减小尺寸后显示出在带边吸收附近的逐渐蓝移，对选择性多色光电检测很有用。进行从室温（300 K）到10 K的随温度变化的光致发光测量。最有趣的是 与通常在块状半导体和直径较大的BP NC中通常观察到的正热淬火相比，具有最小直径的BP NC具有新颖的负热淬火行为。制作了金属-半导体-金属类型（Au / BP-NCs / Au）光电探测器以研究其光响应特性，从而揭示了BP NC作为光调制器的潜在应用。