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Quantum dots for temperature sensing

Doskaliuk Natalia, Lukan Yuliana, Khalavka Yuriy

Scientiae Radices

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2023

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Vol. 2, Iss. 2

93--111

EN

Quantum dots are three-dimensional nanoparticles of semiconductors with typical sizes ranging from 2 to 10 nm. Due to the quantum confinement effect the energy gap increase with the size decreasing resulting in size-depended and fine-tunable optical characteristics. Besides this, the energy structure of a quantum dot with a certain size is highly sensitive to environmental conditions. These specific properties open a wide range of applications starting from optical and optoelectronic devices and ending with biosensing and life science. Temperature is one of those parameters influencing strongly on the optical properties of semiconductor nanocrystals, which make them promising materials for temperature sensing, more often using a fluorescent response. Compared to the conventional organic dyes already applied in this field, quantum dots exhibit a set of advantages, such as high quantum yield and photostability, long fluorescence lifetime, higher Stokes shift, and ability to surface functionalization with targeted organic molecules aimed to provide them biocompatibility. In this review, we briefly discuss the properties of II-VI and assumingly less toxic I-III-VI quantum dots, mechanisms of temperature-induced fluorescence response, and the feasibility of their practical application in the field of thermal sensing.

2

Hybrid white light emitting devices (HWLEDs) from organic polymer and PbS nanocrystals by multiple excitons

Kadim Akeel M.

Materials Science Poland

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2020

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Vol. 38, No. 4

693--698

EN

Hybrid white light-emitting devices (HWLEDs) were fabricated using FTO/PEDOT: PSS/PbS/Alq3/Ni system and synthesized by phase separation process. In the present study, the multiple excitons generation in lead sulfide (PbS) NCs, which is characteristic of PbS NCs, was used to induce an effective and regulated energy transfer to an HWLED. The HWLED consisted of three layers successively deposited on FTO glass substrate; the first layer consisted of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) blended with polymethyl methacrylate (PMMA) organic polymer in the 1:1 ratio, while the second layer consisted of PbS NCs. Finally, above the layer of the PbS NCs, Tris (8-hydroxyquinoline) aluminum (Alq3) layer was deposited. The white light was generated with quite a good efficiency due to the confinement effect that makes the energy gap greater. The characteristics of the current-voltage (I-V) indicate acceptable conditions for the generation of white light by multiple excitons. It was found that the emission levels able to produce white luminescence, classified based on the coordinate system of chromaticity (CIE 1931), are x = 0.31, y = 0.33 while the correlated color temperature (CCT) is about 6250 K. The HWLEDs made from PbS NCs with hole injection from the organic polymer (PEDOT: PSS with PMMA), and electron injection from organic molecules (Alq3) are capable of white light generation.

3

Hydrothermal synthesis and thermoelectric properties of PbS

Zhang H., Wang H., Zhu H., Li H., Su T., Li S., Hu M., Fan H.

Materials Science Poland

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2016

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Vol. 34, No. 4

754--759

EN

In this paper, hydrothermal approach combined with high pressure sintering method was employed to synthesize PbS. The X-ray diffraction results show that single phase PbS can be obtained by a simple hydrothermal method. The scanning electron microscope results show that the PbS sample has nearly cubic shape and preserves well crystallized and coarse grains after high pressure sintering. The thermoelectric performance of PbS obtained in this study is comparable to that of a PbS sample prepared by conventional method. The carrier type and concentration of PbS can be tuned effectively by doping with Bi. The maximum figure of merit for PbS doped with 1 mol% Bi reaches 0.44 at 550 K, which is about 30 % higher than that of undoped PbS. These results indicate that hydrothermal method provides a viable and controllable way of tuning the electrical transport and thermoelectric properties for PbS.

4

Chemically synthesized PbS nanoparticulate thin films for a rapid NO2 gas sensor

Burungale V. V., Devan R. S., Pawar S. A., Harale N. S., Patil V. L., Rao V. K., Ma Y. R., Ae J. E., Kim J. H., Patil P. S.

Materials Science Poland

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2016

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Vol. 34, No. 1

204--211

EN

Rapid NO2 gas sensor has been developed based on PbS nanoparticulate thin films synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method at different precursor concentrations. The structural and morphological properties were investigated by means of X-ray diffraction and field emission scanning electron microscope. NO2 gas sensing properties of PbS thin films deposited at different concentrations were tested. PbS film with 0.25 M precursor concentration showed the highest sensitivity. In order to optimize the operating temperature, the sensitivity of the sensor to 50 ppm NO2 gas was measured at different operating temperatures, from 50 to 200 degrees C. The gas sensitivity increased with an increase in operating temperature and achieved the maximum value at 150 degrees C, followed by a decrease in sensitivity with further increase of the operating temperature. The sensitivity was about 35 % for 50 ppm NO2 at 150 degrees C with rapid response time of 6 s. T90 and T10 recovery time was 97 s at this gas concentration.

5

Optymalizacja warunków otrzymywania kropek kwantowych metodą SILAR

Trenczek-Zając A., Łącz A., Ziąbka M., Radecka M.

Materiały Ceramiczne

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2014

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T. 66, nr 1

49--54

PL

W celu otrzymania kropek kwantowych PbS i CdS zastosowano metodę adsorpcji kolejnych warstw jonów i reakcji (SILAR) z wykorzystaniem roztworów siarczku(II) sodu, azotanu(V) ołowiu(II) i siarczanu(VI) kadmu na bazie wody destylowanej lub metanolu. Zastosowano stężenia z zakresu 0,001-0,1 M oraz liczbę cykli osadzania zmieniającą się w granicach 5-15. Obecność poszczególnych pierwiastków w otrzymanych strukturach potwierdzona została analizą widma EDS. Na podstawie wyników XRD stwierdzono, że zarówno PbS jak i CdS krystalizują w układzie regularnym. Analiza zdjęć otrzymanych metodą SEM pozwoliła na określenie zależności pomiędzy parametrami procesu SILAR, takimi jak stężenie roztworów prekursorów, liczba cykli osadzania i rodzaj rozpuszczalnika, a rozmiarem nanostruktur PbS i CdS. W przypadku obu siarczków, zastosowanie roztworów wodnych prekursorów o stężeniu nie przekraczającym 0,01 M stwarza warunki do krystalizacji pojedynczych kropek kwantowych, których rozmiar rośnie wraz ze wzrostem stężenia. Analogiczne zależności obserwowane są w przypadku zwiększania liczby cykli, bez względu na rodzaj rozpuszczalnika. Stosowanie roztworów wodnych o większym stężeniu (≥ 0,1 M) prowadzi do częściowej aglomeracji. Zmiana rozpuszczalnika na metanol pozwala na zmniejszenie rozmiaru nanostruktur.

EN

In order to deposit quantum dots of PbS and CdS successive ionic layer adsorption and reaction, SILAR route was employed. Water- and methanol-based solutions of sodium sulfide(II), lead(II) nitrate and cadmium sulfate were used. A concentration of solutions varied from 0.001-0.1 M and a number of cycles changed from 5-15. The EDS analysis confirmed the presence of sulphur and lead or cadmium in the obtained structures. Based on the XRD results it was found that both PbS and CdS crystallizeed in the cubic structure. SEM images allowed us to determine the relationship between size of deposited QDs and SILAR parameters such as the solution concentration, the number of cycles and the solvent type. In the case of both sulphides, deposition from the water-based solutions of concentrations up to 0.01 M creates the conditions suitable for crystallization of individual QDs. Along with the increase in the solution concentration the size of QDs increases. Similar effects are observed in case of the increase in the number of cycles regardless of the solvent type. The usage of more concentrated solutions (≥ 0.1 M) leads to partial agglomeration. Changing the solvent to methanol leads to smaller nanostructures.

6

Nanoparticles of lead sulfide in porous glasses prepared by the sol-gel method

Reisfeld R., Sarajdarov T., Minti H., Wodnicka K.

Optica Applicata

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2003

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Vol. 33, nr 1

61-73

EN

PbS semiconductor nanoparticles were grown inside the matrices of zirconium oxide (ZrO2) and zirconium-silica-polyurethane (ZSUR) prepared by the sol-gel method. Zirconium ormosil included polyurethane used to control the growth and aggregation of PbS nanoparticles. The new matrix allows the incorporation of up to 40% PbS forming a characteristic structure of dendrite by reacting lead acetate with ammonium thiocyanate in the sol-gel matrix. The sol precursors of the matrix for ZSUR contain ZrO2 matrix solution, epoxy-silica-ormosil (ESOR) and diurethane siloxane (DURS) synthesized separately. The size of nanoparticles as determined by transmission electron microscopy (TEM) ranges between 2–4 nm for 20% PbS in zirconium oxide and 8–10 nm for 20% PbS in ZSUR matrices. The porosity of the glasses is determined using the nitrogen adsorption technique. The pore size for ZSUR doped with 2% of PbS as determined by BET is 1.54 nm. Quantum size effect was observed from the shifts of absorption and photoluminescence (PL).