Optical Characterization of Colloidal AgInS2 Quantum Dots Synthesized from Aqueous Solutions

Abstract

Colloidal AgInS2 quantum dots (QDs) with intense broadband photoluminescence (PL) were synthesized in aqueous solutions in the presence of glutathione at mild conditions. Size-selective fractioning of QDs was performed by repeated centrifugation of the colloidal solution with the addition of 2-propanol. Based on the optical absorption and PL data, the dependences of the band gap and the PL maximum position on the QD size are analyzed. The Raman spectra of AgInS2 QDs exhibit only a slight variation with decreasing QD size explained by phonon confinement. Changes in the Raman spectra with increasing laser power density are most likely related to photoinduced oxidation of the AgInS2 QD surface with the formation of S-O bonds.

Glutathione-Capped Quaternary Ag–(In,Ga)–S Quantum Dots Obtained by Colloidal Synthesis in Aqueous Solutions

“…However, no drastic differences of the signal-to-noise ratio were observed. Note that an earlier study of Raman scattering for size-selected AgInS 2 QDs [34] where the bandgap was varied for the QDs of different sizes, did not reveal any pronounced resonant behavior either. The targeted Raman study of small-size (3-5 nm) non-stoichiometric Ag-(In)-S QDs [41] did not report drastic resonance-related effects, although a redistribution of intensities for 𝜆 exc = 633 nm and a noticeably worse single-to-noise ratio for 𝜆 exc = = 325 nm (both quite away from the bandgap value for the major part of the QDs in the polydisperse ensemble) were observed.…”

“…In all cases, the observed first-order spectra were approximated by a superposition of overlapping vibrational peaks, their number ranging from 4 [38] up to 10 [41]. Interestingly, Raman scattering in Ag-In-S QDs is studied much more widely [21,34,38,39,41,46,57,59] than in bulk AgInS 2 crystals, for which, to our knowledge, the only experimental Raman data currently available refer to unpolarized spectra of polycrystalline AgInS 2 [60].…”

“…The colloidal synthesis of Ag-(In,Ga)-S QDs, including the end-point Ag-In-S and Ag-Ga-S ternary compounds, was based on an exchange reaction between Na 2 S and a mixture of Ag(I), In(III), and Ga(III) thiolate complexes in the desired proportions with GSH in an aqueous solution (with addition of NH 4 OH) at mild heating (93-98 ∘ C) similarly to the earlier reports on obtaining brightly luminescent Ag-In-S [10,11,33,34], Cu-In-S [35,36], and Ag-Ga-S [37] QDs. We gave preference to GSH over MAA for the synthesis, since formerly [38] we found that GSHcapped Ag-In-S QDs exhibit a better stability upon long-term room-temperature storage than those stabilised by MAA.…”

Structural and Optical Characterisation of Size-Selected Glutathione-Capped Colloidal Cu–In–S Quantum Dots

“…On the other hand, it is known that, for various sulphide materials, especially in disordered systems [61,62], a band attributed to homopolar S-S vibrations is known to be observed in the frequency imterval 430-490 cm −1 . In particular, it was reported in the earlier studies of colloidal AgIn𝑆 2 QDs obtained by a similar method as a broad band near 450 cm −1 [63,64].…”

A Study of Photoreactivity of Inorganic Nanocrystals with Significant Organic Colors

“…This means that the development of novel lasers, LEDs, solar cells, and other optoelectronic devices is possible. Since QDs have a small emission range and their highest peak emission wavelength is located within the visible spectral range, these materials hold considerable promise for improving the photometric and colorimetric features of white LEDs [13]. This allows for numerous QD emitters finely tuned one at a time to generate the desired spectrum collectively.…”