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Sains Malaysiana 47(11)(2018): 2841–2849 http://dx.doi.org/10.17576/jsm-2018-4711-27
Kajian terhadap Sifat Optik Titik
Kuantum Kadmium Sulfida pada Pelbagai Nilai pH dan Modifikasi
Permukaan dengan Asid Tioglikolik (Study on Optical Properties of Cadmium
Sulphide Quantum Dots in Various pH Values and Surface Modification
by Thioglycolic Acid) SITI AISYAH
SHAMSUDIN*
& JENNIVER JUNAS School of Applied Physics, Faculty
of Science and Technology, Universiti Kebangsaan Malaysia, 43600
UKM Bangi, Selangor Darul Ehsan, Malaysia Diserahkan: 30 April 2018/Diterima:
2 Ogos 2018 ABSTRAK Pengimejan tradisi mempunyai
banyak kekurangan seperti mempunyai jangka hayat yang pendek serta
bersaiz besar kerana sifat pendafluornya tidak tahan lama atau
berlakunya pelunturanfoto. Melalui kajian ini, nanohablur kadmium
sulfida dihasilkan dan berfungsi sebagai pengimejan titik kuantum
yang sesuai dengan sifat optiknya yang pelbagai mengikut saiz
zarahnya. Sifat optik titik kuantum kadmium sulfida (TK
CdS) boleh dipengaruhi oleh saiz dan juga komposisi
kimia TK
seperti perubahan pH. Dalam kajian ini, sifat optik
TK CdS
dikaji terhadap perubahan nilai pH dengan menghasilkan TK CdS
melalui kaedah koloidal. Kadmium asetat dihidrat (C4H6CdO4.2H2O)
dan natrium sulfida (Na2S) digunakan sebagai sebagai bahan pemula
bagi menghasilkan TK CdS. Nilai pH diubah suai dengan menitiskan
natrium hidroksida (NaOH) ke dalam larutan TK CdS.
Lima jenis larutan disediakan iaitu pada nilai pH5, pH7, pH8,
pH9 dan pH10. Masalah penggumpalan sering berlaku semasa proses
sintesis CdS. Oleh itu, kajian ini menggunakan asid tioglikolik
(HSCH2CO2H)
sebagai agen penstabil kepada TK CdS. Spektra keserapan UV
memberi anjakan biru apabila TK CdS pada pH alkali kerana saiz nanohablur
mengecil. Hasil daripada spektroskopi pendarfluor mendapati larutan
yang mempunyai nilai pH8 memberi puncak yang tertinggi. Hal ini
adalah kerana pada pH ini nanohablur mampu berubah pada posisi
yang tepat dan membentuk TK
CdS pada kehabluran yang tinggi. Oleh itu, mekanisme
ini dapat membentuk perangkap lubang dan seterusnya eksiton terbentuk.
Kata kunci: Asid tioglikolik;
nilai pH; sifat optik; titik kuantum kadmium sulfide ABSTRACT Traditional imaging has many
drawbacks such as a short lifetime and larger particles’ sizes
as the result the fluorescence property does not long lasting
due to the photo-bleaching phenomenon. Via this study, nanocrystal
cadmium sulphide has been synthesized and functioned as a quantum
dot imaging corresponding to optical properties that vary with
particle size. Optical properties of the quantum dots of cadmium
sulphide (CdS QDs) can be changed by particles’ size and also of the chemical
composition while synthesis such as pH values. In this study,
the optical properties of CdS QDs were studied against the change in
the pH values by preparing CdS QDs via the colloidal method.
Cadmium acetate dehydrated (C4H6CdO4.2H2O)
and sodium sulphide (Na2S) are used as the precursors for producing
CdS QDs. The pH values are modified by titrating sodium hydroxide
(NaOH) into CdS QDs’ aqueous solution. Five pH values
of aqueous solutions at pH5, pH7, pH8, pH9 and pH10 were prepared
however, agglomeration often occurs during the synthesising process.
Therefore, thioglycolic acid (HSCH2CO2H)
was used as a stabilizer agent for CdS QDs. UV-vis
Spectra have shown blue-shifted when CdS QDs on the alkaline medium due
to the nanocrystals’ sizes are decreased. The result from fluorescence
spectroscopy has given the CdS QDs in pH8 gives the highest peak
compared to others pH values. This happened because at this pH
value, the nanocrystalline is able to change to the right position
and formed the CdS QDs
with high crystallization. Thus, this mechanisms of the occurrence
of the trap hole obtained and caused the exciton. Keywords: CdS quantum dot; optical properties; pH value; thioglycolic
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email: aisyah@ukm.edu.my
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