A known property of QDs is their characteristic luminescence, which would make it possible to detect different types of cancers after being functionalized with some type of biological molecule. For this reason, in the present investigation a methodological analysis of the physicochemical characteristics of the CdTe/ZnS core/shell QDs was carried out, using techniques such as UV-Vis absorbance, Molecular Fluorescence, FT-IR, DLS and Zeta Potential that allowed to verify the photoluminescent effectiveness of these semiconductor nanocrystals as an alternative to conventional techniques currently used for the detection of specific cancers smaller than 1cm. The study consisted of theoretically determining the bandgap energy, the size of the nanocrystals and the molar absorptivity from the wavelength value for the maximum intensity of the excitonic peak. It was also possible to verify the maximum intensity for each sample and thus evaluate its photoluminescent response, as well as it was possible to determine the charge distribution, the hydrodynamic size and the surface composition of each quantum dot. The results obtained correspond to what has been reported in the literature, which makes them good candidates for the detection of cancer in precancerous stages.
Research Article
One-pot synthesis of CdTe/ZnS quantum dots and their physico- chemical characterization
https://doi.org/10.21203/rs.3.rs-3140425/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 25 Aug, 2023
You are reading this latest preprint version
Quantum Dots
CdTe
ZnS
Core Shell
Biosensors
Nanotechnology has become a key area in the scientific community from the early 1990s [1]. Thence, the considerable development of some of its most important branches such as nanomedicine and nanodiagnostics, have allowed to know and study with depth of different types of diseases that can directly affect different parts of the human body, since their earliest stages using nanodevices [2].
Cancer belongs to this group of diseases, which can be expressed in uncontrolled cell changes and cell division as common symptoms of the disease. Some types of cancer cause the cell to grow rapidly, while others cause the cells to grow and divide at a slower rate. However, when these changes reach the metastatic stage, it can lead to the death of the patient [3–5]. Nowadays, the use of chemical sensors, nanosensors and biosensors to measure low concentrations of pharmacological compounds seems too attractive [6]. The sensor is actually a chemical device or species that is capable of reversibly interacting with the analyte. This interaction is observed by color and fluorescence changes [7]. Among the different types of sensors, quantum dot nanosensors have received the most attention due to their dimensions providing very high precision and reactivity which are comparable in size to most biological molecules making them one of the most used and promising nanomaterials today. However, QDs can be toxic, so they must be protected with organic polymers or with an ultra-thin layer of inorganic material deposited on the nanocrystal surface (core/shell system) [8].
Quantum dots (QDs) are semiconductor nanocrystals that emit and absorb energy at different wavelengths. They are considered as artificial atoms because their energy levels are discretized because of the quantum confinement effect. The quantum confinement is reached when a semiconductor material is synthesized with building blocks sized in at least one of its dimensions smaller than the exciton Bohr-radius of the corresponding semiconductor material. Quantum dots, therefore, exhibit the phenomenon of quantum confinement in its three dimensions [9–11]. Furthermore, these semiconductor nanoparticles overcome the limitations of current conventional markers, as they are highly capable of being exposed to excitation and photoluminescence cycles for several days without losing their efficiency. Quantum dots are resistant to metabolic degradation, high extinction coefficients, and can act as detectors when conjugated with some type of biomolecule [1]. Since QDs are used at low concentrations in these experiments and no organic solvents are used to measure the analyte, environmental contamination is minimal when working with these type of semiconductor nanomaterials [12].
Quantum dots that have been successfully applied in technology and biomedical areas, they are composed of elements belonging to groups II-VI, III-V, or IV-VI of the periodic table [13–14], and they can be structured by a core/shell system [1]. In the present research, an inorganic core of CdTe, a shell of ZnS, and an external organic layer of 3-mercaptopropionic acid molecules, covering up the QDs analyzed. Additionally, emission properties emerge from the quantum confinement effect, through which electronic excitations are sensitive to the presence of nanocrystal boundaries and respond to changes in its size, adjusting its energy spectrum. In this way, the properties of the particle, such as its optical absorption and its emission depend on particle the size. As a consequence, the size effect on electrons and holes competes with the coulombic interaction between them. [15]
To prevent the effects of toxicity by a possible diffusion of metals due to the oxidation of the imperfections on the nanocrystal surface, a shell of nontoxic material is deposited on nanocrystal surface. In this case, the synthesis of materials for core/shell (CS) structures depends on the band gap energy and the location of the energy levels of the semiconductor electronic components [16–19]. In the present research, ZnS was deposited on the CdTe nanocrystal surface since this compound is not dangerous for living organisms and is a chemically stable semiconductor material. [20] Furthermore, this compound has a band gap of 3.6 eV, larger than of uncoated CdTe (1.43 eV), which reduces the probability of non-radiative recombination at trap sites due to the electron wave function in the central region is confined [21–22]. This coating would increase the quantum yield, photostability, and dispersibility of CdTe QDs stabilized with mercaptopropionic acid making them a better fluorescent probe in biomedical application [23], compared to organic fluorescence, as the wavelength of tunable emission, multi-application capabilities and high photoluminescence [24].
A solution for the preparation of CdTe nanocrystals were prepared at room temperature by a one-pot synthesis reported elsewhere [25]. Then, the solutions were subjected to a chemical treatment to form a CdTe/ZnS core/shell system, for which precursor solutions of zinc chloride (ZnCl2) and thiourea (CH4N2S) were used, with equimolar concentrations of 0.04 M (Sample 1) and 0.08 M (Sample 2). Whit a relation 8 :1:1 CdTe:ZnCl2:thiourea. Subsequently samples were heated on a hot plate for 1 hour at 100°C to activate their luminescence and then proceed to their characterization.
Optical Absorbance Spectroscopy
To determine the wavelength of the maximum of optical absorption, that is, the position of the maximum of the excitonic peaks, the samples were characterized by optical absorbance spectroscopy, using a Shimadzu UV-1800 spectrophotometer, in the electromagnetic spectrum from ultraviolet to visible.
Dynamic Light Scattering and Zeta Potential
For the experimental determination of the hydrodynamic size of QDs, and their Zeta Potential, a particle analyzer, Anton Paar Litesizer 500, at a wavelength of 660 nm, with a refractive index of 2.456, and an absorption coefficient of 1.0m− 1 was employed. All measurements were made at normal incidence.
Previously, two filtrations of both samples (Sample 1 and Sample 2) were carried out to avoid a possible agglomeration of the nanocrystals in the solution. The particle size distribution was measured by depositing 1 mL of QDs solution in a 105.202-QS type quartz cell. Secondly, the determination of Zeta Potential of the samples was carried out using a 0.8mL OMEGA JVLAB acrylic cell.
Molecular Fluorescence
Fluorescence was measured at room temperature by a Jasco FP-8200 Hellma spectrofluorometer, and 105.202-QS quartz cuvettes were used. The measurement was performed under optical excitation of 466nm, and the detector was adjusted to low sensitivity.
Fourier Transform Infrared Spectroscopy (FT-IR)
FT-IR measurements were made with a Shimadzu Prestige 21 spectrophotometer. An aliquot of 5 mL of sample were placed on a porcelain capsule and dried in an oven at room temperature for five days until complete water evaporation was achieved. Subsequently, 100 mg of potassium bromide were taken and spread throughout the capsule to drag the microparticles of the solid and thus form a tablet that would be placed in the equipment. Spectra were obtained in a wave number interval of 4000 − 600 cm− 1.
Optical Absorbance Spectroscopy.
In Fig. 1, the absorbance spectrum of both CdTe/ZnS quantum dot samples is exhibited. Both the reference sample and Sample 1 (it which contains an equimolar concentration of ZnCl2 and thiourea of 0.04 M), have an excitonic peak with well-defined line shape, and with a mean width at maximum intensity of the order of 40 nm, which indicates that the size distribution is nearly monodisperse. Different case resulted for Sample 2, prepared with an equimolar concentration of ZnCl2 and thiourea of 0.08 M, whose excitonic peak has a widened line shape compared to the other two samples, possibly due to a dispersed size distribution [26–27]. We can also observe that the position of the excitonic peaks of the samples varies slightly with respect to the reference sample, possibly these variations are due to temperature gradients present during the heating process.
Dynamic Light Scattering
Results of DLS measurements are exhibited in Fig. 2, for Sample 1, and Fig. 3, for Sample 2, respectively. The hydrodynamic diameter obtained for Sample 1 was of 4.4 nm, and in the case of Sample 2, the value was 4.9nm. The larger value of the particle size obtained for both samples compared with theoretical calculations for samples whose excitonic peaks are localized in the interval of 400–500 nm [28] (nearly green luminescence), is related to the deposition of a ZnS shell layer and the solvation of the CdTe/ZnS system surface. According to the graphs, there is a distribution of homogeneously sized nanocrystals, with a single mean size population in the case of Sample 1 and with two mean size populations in the case of Sample 2, where one distribution is the majority and the other one is the minority. This result was verified with the DLS results based on size distribution by volume shown in Figs. 2b) and 3 b), respectively.
The second population of particles seen in Fig. 3a) can corresponds to a slight number of agglomerated particles due to the growth of the solvation layer associated with the increase in temperature and concentration due to the functional groups present in the QDs surface. In addition, the presence of ZnS nanocrystals is also possible, whose excitonic peaks are below 400 nm [28.] and have a weak luminescence [29]. However, these bands were not observed in the absorbance and fluorescence spectra of the samples.
On the other hand, Sample 1 exhibited a nearly monodisperse distribution compared to Sample 2, so that a 0.04 M equimolar concentration of ZnCl2 and thiourea allowed uniform deposition of a ZnS layer on the surface of CdTe QDs. For this reason, the excitonic peak of sample 1 resulted in a closely symmetrical line shape, with a mean width at maximum intensity less than that corresponding to Sample 2. This nearly monodisperse feature was also observed in the fluorescence spectrum.
Molecular Fluorescence
The line shape of the photoluminescent emission spectra is also a characteristic measure of the quality, and size distribution of the prepared nanocrystals. The photoluminescence spectra obtained for the studied samples are showed in Fig. 4. Both spectra exhibit a well-defined and intense line shape, within the interval of 480 and 550nm and with peaks of maximum intensity centered at 527nm and 525nm, respectively, producing a nearly green emission. Since samples 1 and 2 exhibit the same luminescent wavelength as the reference sample, in spite quantum dots have hydrodynamic sizes of 4.4 and 4.9 nm, respectively.It follows that the emitting center of CdTe maintains its initial size and therefore an ultra-thin film of ZnS was deposited on its surface. It is well known that the hydrodynamic size includes the CdTe/ZnS core/shell size and part of the ionic atmosphere that moves with it [30].
Making a comparison between both samples, it is possible to conclude that the solvation layer that surrounds and moves with Sample 2 is greater than the one that surrounds Sample 1, and this affects its fluorescence intensity, due the tendency to the molecules agglomeration and therefore there are larger particles inside, which were not excited and therefore did not emit radiation [29]. It must be taken into account that the pH of both samples is different, due to the fact that the concentrations of the ZnS precursors vary. This has an impact on the photoluminescent intensity [31] and is expected to also influence the hydrodynamic surface of the sample, changing its size.
Finally, emission bands relative to ZnS nanocrystals, localized in the blue region of the electromagnetic spectrum, were not observed in the spectra of Fig. 4. We can deduce the second population of nanoparticles exhibited in the size distribution by volume curve corresponding to Sample 2, consist of CdTe/ZnS agglomerates.
Fourier Transform Infrared Spectroscopy
The FT-IR spectra corresponding to 3-MPA and both samples are shown in the Fig. 5, and the Table 1 summarizes the main absorption bands, characteristics of functional groups of 3-MPA molecule. The characteristic absorption band of the C = O vibration of 3-MPA (1726 cm-1) for the case of both samples has been displaced to lower frequencies. This can be due to the inductive (-I) and mesomeric (+ M) effects of the functional R-SH- [31], or also due to the presence of carboxylate ions (R-COO-) on the surface of both samples. [32] This hydrophilic group is responsible for the negative charge on said surface, making the nanoparticle an excellent candidate for realize another external bonds [33], that is, functionalize. In addition, it is observed how the ionization of the COOH makes the two C-O bonds equivalent, which gives rise to an intense condenser of oscillators. Indeed, this shift occurs when the thiol group, through sulphur ion (R-S) had some chemical activity, such as the formation of a bond with a zinc since the synthesis is considered to result in a CdTe/ZnS core/shell system ion located on the surface of the CdTe/ZnS core/shell. It is also possible to identify in the samples a mode which is not observed in the FT-IR of 3-MPA. It is the asymmetric mode of the C-O-H anion, around 1398 cm-1, this may be due to QDs dispersion effects in the aqueoussolution. [34] With these results it is verified that the 3-MPA molecule binds to the surface of the quantum dot, possibly through a superficial zinc ion and the other end of the molecule provides solubility in aqueous solution to the nanostructure.
The bond corresponding to the H-S thiol group is a weak bond, which is easily broken once the 3-MPA is dissolved in water, so the H-S vibrational mode disappears before the 3-MPA molecule anchors to the nanocrystal surface.[35]
Zeta Potential
The results of the Z potential measurements for the samples are presented in Fig. 6. According to FT-IR spectroscopy results discussed in the previous section, we expect that QDs surface gets negatively charged, since the carboxyl group provides a negative charge when is dissociating in carboxylate ions. Therefore, the carboxyl functional remains outside the sphere of coordination and is available to conjugate with any molecule of the biological type, while, inside the quantum dot, the R-SH- group is found coordinating the zinc ions (Zn-S) in excess on QDs surface.in Fig. 6, the distribution of the Zeta Potential is showed, and its corresponding negative values are reported in Table 2. The different concentration values of charges in Sample 2 with respect to Sample 1 are due to the difference in charges existing between the surface, that is, the solvation layer, and the interior of the nanoparticle. The value of the distribution peak for Sample 1 is positive due to a higher concentration of Cd2+ and Zn2+ ions that remained in excess once coordination was established. These results are consistent with what was obtained by Carrasco, D.E in 2021 with his work on the synthesis and characterization of QDs of g-C3N4 and its application in fluorescence detection systems [36].
Both the position of the distribution peak, as well as the negative zeta potential values for the samples indicate that they meet the requirements to be functionalized for biological labeling. These results corroborate the presence mostly of carboxylate groups responsible for the negative charges on the surface.
Table 2: Measurement statistics for samples 1 and 2.
In this research CdTe/ZnS quantum dots were analyzed to verify their effectiveness for future bioconjugation that allows for the detection of tissues and malignant tumors up to less than 1 cm in diameter. The possible functional groups present in each sample of quantum dot were checked by FT-IR where the presence of the R-COOH group in resonance with the free R-COO in the coordination sphere was demonstrated and no characteristic bands of SH- were observed indicating that the bond between the core/shell and the ligand is through it. By means of the Zeta potential technique the above is corroborated since negative values corresponding to the presence of the carboxylate group on the surface of the quantum dot were obtained
Using the DLS technique,it was verified that the hydrodynamic diameter of quantum dots exceeded the theoretical value, due to deposition of an ultra-thin film of ZnS on the quantum dots surface and the entire ionic atmosphere that surrounds it. Additionally, it was possible to verify the improvement of the optical properties of samples by means of UV-Vis and Molecular Fluorescence, on the one hand the particle size distribution and on the other the intensity of luminescence. The full width at maximum intensity of fluorescence peak as well as the results by dynamic light scattering, indicated that, quantum dots are nearly monodispersed. The hydrodynamic size was of 4.4 nm for the best sample, which an equimolar concentration of ZnCl2 and thiourea of 0.04 M was used.
Quantum dots, based on CdTe/ZnS, can be considered as efficient markers in the detection of cellular abnormalities due to their high photoluminescence and their stability in aqueous medium. For this reason and taking into account their other applications, it is expected that bioconjugate materials may have special relevance in biological studies and in the possibility of improving the quality of life of human beings.
Funding
This work was supported by programa de apoyo a la investigación científica y tecnológica 2022 UANL 244-CE-2022
Competing Interests
The authors declare no competing interests
Author Contributions
Francisco Solis-Pomar, C. D. Gutiérrez-Lazos, Eduardo Pérez-Tijerina and Abel Fundora Cruz contributed to the study conception and design. Gabriela Travieso Aguilar, Francisco Solís-Pomar, C. D. Gutiérrez-Lazos, Eduardo Pérez-Tijerina, Abel Fundora Cruz contributed to data interpretation and manuscript drafting. Gabriela Travieso Aguilar, Maykel Márquez Mijares, Francisco Solís-Pomar, C. D. Gutiérrez-Lazos contributed Material preparation, data collection and analysis
Data Availability
All data are available as part of the article
Ethics approval
n/a
Consent to participate
n/a
Consent to publish
n/a
- Sánchez, A. (2016) Síntesis y caracterización de puntos cuánticos de PbSe con aplicaciones en celdas fotovoltaicas con configuración FTO/TiO2/CdS/PbSe/ZnS. Tesis para obtener el grado de Máster en Ciencias. Universidad de Guanajuato, México. http://cio.repositorioinstitucional.mx/jspui/handle/1002/295
- Mejías, Y et al (2009) “La nanotecnología y sus posibilidades de aplicación en el campo científico-tecnológico,” Revista Cubana de Salud Pública. Vol. 35, No. 3, Pp. 1–9. http://scielo.sld.cu/scielo.php?script=sci_arttext&pid=S0864-34662009000300006
- Bardajee G R et.al. (2021) Capacidad de la nueva nanosonda de puntos cuánticos de CdTe/ZnS conjugada con ADN fluorescente para la detección de COVID-19. Journal Medbiotech. Vol.5. No. 2. Pp. 23-26. https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.sciencedirect.com/science/article/abs/pii/S1386142521012798&ved=
2ahUKEwioidPqhOr_AhU0FlkFHbFmDrAQFnoECA4QAQ&usg=AOvVaw1sAX4H1ENFaJn21-P8C6di - Uribe C J, Sánchez C M, Serrano S E (2018), Cancer incidence and mortality in Bucaramanga, Colombia. 2008-2012, Colombia Médica Vol 49 No.1. Pp. 73-80. http://www.scielo.org.co/scielo.php?pid=S1657-95342018000100073&script=sci_arttext
- Acosta, Á. E., Fierro, E., Velásquez, V. E., & Rueda, X. (2009). Melanoma: patogénesis, clínica e histopatología. Rev Asoc Col de Dermatol. Vol 17, No. 2 Pp. 87-108. https://revistasocolderma.org/articulo-revista/melanoma-patogenesis-clinica-e-histopatologia
- Majeed M I, Nawaz H, Arshad F N. (2020). Detecting the Presence of Illicit Drugs Using Biosensors. Nanobiosensors: From Design to Applications, 223-253. https://onlinelibrary.wiley.com/doi/abs/10.1002/9783527345137.ch10
- Wilson, J. S. (2005). Sensor technology handbook. Editor: Jon S. Wilson. Elsevier. https://books.google.es/books?hl=es&lr=&id=5UE6YCjDG-MC&oi=fnd&pg=PP1&dq=7.%09Wilson,+J.+S.+(2004).+Sensor+technology+handbook.+Elsevier.&ots=jgOYh9gKK1&sig=NZOC1iboO3Snuf0Ec-ds97aahSw#v=onepage&q&f=false
- Woldu, M A, Lenjissa, J L, & Satessa, G. D. (2014). Design and Evaluation of Nanoparticulate Drug Delivery Systems for Imaging and Treatment of Malignant Brain Tumor. Global Journal of Science Frontier Research: G Bio-Tech & Genetics, Vol.14. No 1. https://www.academia.edu/11306878/Design_and_Evaluation_of_Nanoparticulate_Drug_Delivery_Systems_for_Imaging_and_Treatment_of_Malignant_Brain_Tumor
- Cardoso, M, Algar W R, Medintz I L, Hildebrandt, N. (2020). Quantum Dots for Förster Resonance Energy Transfer (FRET). TrAC Trends in Analytical Chemistry, 125. No. 115819. https://www.sciencedirect.com/science/article/abs/pii/S0165993619306612
- Sun, J., Cui, F., Zhang, R., Gao, Z., Ji, J., Ren, Y, Sun, X. (2018). Comet-like Heterodimers “Gold Nanoflower @Graphene Quantum Dots” probe with FRET “Off” to DNA circuit signal “On” for sensing and imaging microRNA in vitro and in vivo. Analytical chemistry. Vol. 90 No.1. Pp. 11538-11547. https://doi.org/10.1021/acs.analchem.8b02854
- Kumar, N, Kumbhat S. Essential in Nanoscience and Nanotechnology. Editado por John Wiley & Song. Library of Congress Cataloging-in Publication. New York. https://www.google.com.cu/books/edition/Essentials_in_Nanoscience_and_Nanotechno/jVTWCwAAQBAJ?hl=es&gbpv=1&dq=Quantum+dots,+therefore,+exhibit+the+phenomenon+of+quantum+confinement+in+its+three+dimensions&pg=PA329&printsec=frontcover
- Ensafi, A A, Kazemifard, N, Rezaei, B. (2015) A simple and rapid label-free fluorimetric biosensor for protamine detection based on glutathione-capped CdTe quantum dots aggregation. Biosensors and Bioelectronics, 71. Pp. 243-248. Doi: 10.1016/j.bios.2015.04.015
- Xie, S., Beni, M. S., Cai, J., & Zhao, J. (2018). Review of critical-heat-flux enhancement methods. International Journal of Heat and Mass Transfer, 122, 275-289. https://doi.org/10.1016/j.ijheatmasstransfer.2018.01.116
- Liang, X., Wu, T., Wang, Y., Wei, T., Zou, L., Bai, C., ... & Tang, M. (2020). CdTe and CdTe@ ZnS quantum dots induce IL-1ß-mediated inflammation and pyroptosis in microglia. Toxicology in Vitro, 65, 104827. https://pubmed.ncbi.nlm.nih.gov/32179110/
- Castillo, L.A. (2017) Incidencia de la NIIF 15 en la situación económica y financiera de la empresa Servicios Eléctricos Laredo S.A.C, Distrito de Trujillo, en el ano 20217. Informe Final De Prácticas Pre Profesionales Presentado En El Cumplimiento A Los Requisitos Para Optar Por El Título De Licenciado En Física. Universidad De Trujillo. México. http://repositorio.upao.edu.pe/handle/20.500.12759/4319
- S Rakshath, B Suresha, R Sasi Kumar, I Saravanan (2020) Dry sliding and abrasive wear behaviour of Al-7075 reinforced with alumina and boron nitride particulates.Materials Today: Proceedings. Vol. 626 no 22. Pp. 619-626 https://scholar.google.es/scholar?hl=es&as_sdt=0%2C5&q=S.+Subramanian.++Materials+Today%3A+Proceedings.+Vol.+626.+.2020&btnG=#d=gs_qabs&t=1688169344586&u=%23p%3DsipVi3yldv8J
- Nguyen, X. C., & Nguyen, T. H. (2020). Phonon Characterization, Structural and Optical Properties of Type-II CdSe/CdTe core/shell and Type-II/type-I CdSe/CdTe/ZnS core/shell/shell Quantum Dots. VNU Journal of Science: Mathematics-Physics, Vol 36 No.3 https://doi.org/10.25073/2588-1124/vnumap.4452
- Reiss P. Carriere, M. Lincheneau, Ch et al. (2016) Synthesis of Semiconductor Nanocrystals, Focusing on Nontoxic and Earth-Abundant Materials. Chemical Reviews 116(18) DOI: 10.1021/acs.chemrev.6b00116
- Zhang, W., Chen, G., Wang, J., Ye, B. C., & Zhong, X. (2009). Design and synthesis of highly luminescent near-infrared-emitting water-soluble CdTe/CdSe/ZnS core/shell/shell quantum dots. Inorganic chemistry, Vol. 48 No. 20. 9723-9731. https://doi.org/10.1021/ic9010949
- Sanjay, S., Prabakaran, K., & Baskar, K. (2020). Epitaxy of gallium nitride pyramids on few layer graphene for metal-semiconductor-metal based photodetectors. Materials Chemistry and Physics, 240, 122189. https://doi.org/10.1016/j.matchemphys.2019.122189
- Coto García, Ana María. "Síntesis y solubilización de Quantum Dots: su aplicación al desarrollo de sensores químicos fotoluminiscentes." (2012). https://dialnet.unirioja.es/servlet/tesis?codigo=75326
- S. Sanjay, K. Prabakaran, K. Baskar. ACS Omega. Vol. 4 Pp.14772–14779.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751544/
- Saikia, D., Chakravarty, S., Sarma, N. S., Bhattacharjee, S., Datta, P., & Adhikary, N. C. (2017). Aqueous synthesis of highly stable CdTe/ZnS Core/Shell quantum dots for bioimaging. Luminescence, 32(3), 401-408. https://doi.org/10.1002/bio.3193
- Roco, E A (2016) Generación de imágenes de microestructuras fluorescentes: un estudio comparativo entre agentes de contraste basados en puntos cuánticos y nanoagregados orgánicos. Tesis Maestría, Centro de Investigaciones en Óptica, AC, León, Guanajuato, México. https://scholar.google.es/scholar?hl=es&as_sdt=0%2C5&q=en+comparaci%C3%B3n+con+la+fluorescencia+org%C3%A1nica+como+la+longitud+de+onda+
de+emisi%C3%B3n+sintonizable+&btnG=#d=gs_qabs&t=1688171146376&u=%23p%3DkLItSxPACC0J - Silva, L.G.; Ruíz, M.A.; Gutierrez,C.D.; Solís, F.; Fundora,A.; Meléndrez,E.; Pérez, E. Chalcogenide. Vol 16. No. 5 (2019) p.241-248. https://chalcogen.ro/241_Silva-VidaurriLG.pdf
- Montes, E. (2015) Síntesis y Caracterización de Quantum-Dots por Difracción de Rayos X y Microscopía Electrónica. Tesis en opción al grado de Máster en Ciencias Analíticas y Bioanalíticas. Universidad de Oviedo. https://digibuo.uniovi.es/dspace/bitstream/handle/10651/31987/TFM_Montes%20Blanco.pdf?sequence=3
- Torresan, M. F. ´´y col´´ (2014) ‘’Metodologías para la obtención de puntos cuánticos de cristales semiconductores de CdSe.’’ Bitácora Digital Cuarto número. Vol. 2 No. 4. Disponible en: https://revistas.unc.edu.ar/index.php/Bitacora/article/view/7511
- Rogach, A. L., Katsikas, L., Kornowski, A., Su, D., Eychmüller, A., & Weller, H. (1996). Synthesis and characterization of thiol‐stabilized CdTe nanocrystals. Berichte der Bunsengesellschaft für physikalische Chemie, 100(11), 1772-1778. https://doi.org/10.1002/bbpc.19961001104
- Gómez-Piñeros, B. S., & Granados-Oliveros, G. (2018). Síntesis y caracterización de las propiedades ópticas de puntos cuánticos de CdSe y CdSe/ZnS. Revista Colombiana de Química, 47(1), 57-63. https://doi.org/10.15446/rev.colomb.quim.v47n1.61067
- Shaw, R. (2022) ANALYTICAL INSTRUMENTS SPECIALISTS. Dynamic Light Scattering Training. Malvern. https://www.atascientific.com.au/
- Xu, S., Wang, C., Zhang, H., Wang, Z., Yang, B., & Cui, Y. (2011). pH-sensitive photoluminescence for aqueous thiol-capped CdTe nanocrystals. Nanotechnology, 22(31), 315703. DOI 10.1088/0957-4484/22/31/315703.
- C.S. Pérez. and P.J. Ortíz. Espectroscopia. Editorial Félix Varela. La Habana. Cuba. 2014. Capítulo 2: Espectroscopia Ultravioleta Visible. Epígrafe: 2.6.9.5 Compuestos titocarbonílicos. https://isbn.cloud/9789590719998/espectroscopia/
- Gutiérrez L. (2019). Estudio de la encapsulación de metalofármacos y su efecto sobre el transporte célular. Tesis en Opción al título de Máster en Ciencias Analíticas y Bioanalíticas. Universidad de Oviedo. https://digibuo.uniovi.es/dspace/handle/10651/59518
- Jiang, H., & Ju, H. (2007). Electrochemiluminescence sensors for scavengers of hydroxyl radical based on its annihilation in CdSe quantum dots film/peroxide system. Analytical chemistry, 79(17), 6690-6696. https://doi.org/10.1021/ac071061j
- Zhai, H., Wang, Y., Wang, M., Liu, S., Yu, F., Gao, C., ... & Wu, Q. (2018). Construction of a glutathione-responsive and silica-based nanocomposite for controlled release of chelator dimercaptosuccinic acid. International journal of molecular sciences, 19(12), 3790. https://doi.org/10.3390/ijms19123790
- D.E. Carrasco. Tesis para obtener el grado MSc. de Ingeniería con orientación en nanotecnología. UANL, México. 2021. http://eprints.uanl.mx/22057/
No competing interests reported.