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<p>In Quantum Dots (QDs), the surface modifications are highly vulnerable due to size and offer superior optical properties. In this study, a fluorescent Cadmium Telluride (CdTe) quantum dots were synthesised via a chemical colloidal method and investigated for the effect of surface passivation on their nonlinear optical properties. The pristine CdTe quantum dots exhibit fluorescence intermittency (blinking), which strongly influences carrier dynamics and results in degraded optical response. To suppress these trap-mediated effects, a passivating agent like β-mercaptoethanol (BME) was introduced as a surface passivating ligand, which improves the surface stability. The synthesised QDs and surface passivated QDs were characterized using UV–Vis absorption, photoluminescence spectroscopy, FTIR, XRD, and TEM, which confirmed particle sizes in the range of 8–11&#xa0;nm. Further, these QDs were investigated for their nonlinear optical response using the z-scan technique. The pristine CdTe quantum dots showed reverse saturable absorption (RSA), whereas BME-passivated CdTe quantum dots showed a transition to saturable absorption (SA), indicating a significant alteration in excited-state absorption dynamics due to surface passivation. Both systems displayed a negative nonlinear refractive index (n₂), confirming self-defocusing behaviour. Furthermore, the BME-induced surface modification enhanced optical confinement (W) and modulation depth (T), suggesting improved nonlinear optical performance. These findings establish that passivation of surface trap states is critical to tuning the nonlinear optical properties of CdTe quantum dots, making BME-passivated CdTe quantum dots promising candidates for optical switching, optical limiting, and other nonlinear photonic applications.</p>

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Surface-driven nonlinear optical responses in CdTe quantum dots: a z-scan approach under diverse conditions

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Rashi Mahendra Patil,
  • Shubhankar Singh Chandel,
  • Akshay Raj,
  • Shyamal Mondal,
  • Tejashree Bhave,
  • Appala Venkata Ramana Murthy

摘要

In Quantum Dots (QDs), the surface modifications are highly vulnerable due to size and offer superior optical properties. In this study, a fluorescent Cadmium Telluride (CdTe) quantum dots were synthesised via a chemical colloidal method and investigated for the effect of surface passivation on their nonlinear optical properties. The pristine CdTe quantum dots exhibit fluorescence intermittency (blinking), which strongly influences carrier dynamics and results in degraded optical response. To suppress these trap-mediated effects, a passivating agent like β-mercaptoethanol (BME) was introduced as a surface passivating ligand, which improves the surface stability. The synthesised QDs and surface passivated QDs were characterized using UV–Vis absorption, photoluminescence spectroscopy, FTIR, XRD, and TEM, which confirmed particle sizes in the range of 8–11 nm. Further, these QDs were investigated for their nonlinear optical response using the z-scan technique. The pristine CdTe quantum dots showed reverse saturable absorption (RSA), whereas BME-passivated CdTe quantum dots showed a transition to saturable absorption (SA), indicating a significant alteration in excited-state absorption dynamics due to surface passivation. Both systems displayed a negative nonlinear refractive index (n₂), confirming self-defocusing behaviour. Furthermore, the BME-induced surface modification enhanced optical confinement (W) and modulation depth (T), suggesting improved nonlinear optical performance. These findings establish that passivation of surface trap states is critical to tuning the nonlinear optical properties of CdTe quantum dots, making BME-passivated CdTe quantum dots promising candidates for optical switching, optical limiting, and other nonlinear photonic applications.