نوع مقاله : مقاله کامل پژوهشی

نویسندگان

1 کارشناسی ارشد، پژوهشکده نیمه‌هادی‌ها، پژوهشگاه مواد و انرژی، مشکین دشت، البرز، ایران

2 دانشیار، پژوهشکده نیمه‌هادی‌ها، پژوهشگاه مواد و انرژی، مشکین دشت، البرز، ایران

چکیده

ویژگی­ های منحصربه­فرد چارچوب­های زئولیتی ایمیدازولی (ZIF) مانند قابلیت تنظیم اندازه حفرات، تنوع ساختاری، پایداری شیمیایی، مکانیکی و حرارتی، این ساختارها را به کاندید مناسبی برای کاربردهای عملی تبدیل کرده است. ازاین‌رو در این کار، ZIF-8، به‌عنوان ماده‌ای مزومتخلخل بر پایه روی (Zn)، به‌وسیله طیف‌سنجی افت انرژی الکترون بازتابی (REELS) و با الگوریتم یوبرو-توگارد که بر اساس نظریه پاسخ دی‌الکتریک بنا شده است، مورد مطالعه قرار گرفت. برون­یابی اعمال‌شده روی طیف REELS، شکاف انرژی (Eg) مربوط به ZIF-8 را 2/4 الکترون‌ولت نشان داد. همچنین تابع افت انرژی سطحی و توده­ای تعیین شد و مقادیر مسافت آزاد میانگین ناکشسان (IMFP) الکترون­ هایی که با انرژی­های متفاوت به ZIF-8 منتقل شده­ اند، مشخص شد و اختلاف آن­ها با مقادیر به‌دست‌آمده، از رابطه تانوما-پاول-پِن (TPP)، مورد بررسی قرار گرفت. افزون ‌براین، از ELF به‌دست‌آمده، با استفاده از تبدیلات کرامرز-کرونیگ، قسمت حقیقی (ε1) و قسمت موهومی (ε2) تابع دی­الکتریک (ε)، ضریب شکست (n)، ضریب میرایی (k)، ضریب بازتاب (R) و ضریب جذب (µ)، به‌عنوان پارامترهای مهم اپتیکی این ماده تعیین شدند.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Determination of Dielectric and Optical Properties of Zeolitic Imidazolate Framework-8 (ZIF-8) by Reflection Electron Energy Loss Spectroscopy (REELS)

نویسندگان [English]

  • Mehdi Pooriraj 1
  • Shaaker Hajati 2
  • Morteza Moradi 2

1 M. Sc., Department of Semiconductors, Materials and Energy Research Center (MERC), MeshkinDasht, Alborz, Iran

2 Associate Professor, Department of Semiconductors, Materials and Energy Research Center (MERC), MeshkinDasht, Alborz, Iran

چکیده [English]

Specific properties such as pore tunability, structural variety as well as chemical, mechanical, and thermal stability, make zeolitic imidazolate frameworks (ZIFs) suitable and of high importance for practical applications. Optical and chemical sensors and supercapacitors are among these applications which necessitate the detailed study of optical and dielectric properties of ZIFs. Therefore, ZIF-8 as a zinc-based mesoporous material was studied by reflection electron energy loss spectroscopy (REELS) applying the Yubero-Tougaard algorithm which is based on dielectric response theory. The band gap energy (Eg) of ZIF-8 was determined to be 4.2 eV using an extrapolation procedure applied to an experimental REELS spectrum. Its bulk and surface energy loss functions were also determined. Inelastic mean free path (IMFP) values of electrons of different energies transported in ZIF-8 were determined and their large differences with values calculated from the Tanuma-Powell-Penn (TPP) formula were discussed. In addition, the obtained ELF was used to apply the Kramers-Kronig transformation to obtain the real part (ε1) and imaginary part (ε2) of the dielectric function (ε), refractive index (n), extinction coefficient (k), reflection coefficient (R) and absorption coefficient (µ) of ZIF-8 as important optical properties of this widely applicable material.

کلیدواژه‌ها [English]

  • Optical Properties
  • Dielectric Properties
  • REELS
  • ZIF-8
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