Application of Quantum Dots in Bio-Sensing, Bio-Imaging, Drug Delivery, Anti-Bacterial Activity, Photo-Thermal, Photo-Dynamic Therapy, and Optoelectronic Devices

Quantum dots (QDs) are of prevalent scientific and technological consideration because of their tunable size and thus frequency change (band-gap energy) in the NIR optical region. QDs have exceptional properties such as optical, physiochemical, electrical, and capacity to be bound to biomolecules. These selective size-dependent attributes of QDs assist them with having versatile applications in optoelectronic and biomedical fields. Their capacity to emit light at various frequencies because of an outer stimulus makes quantum dots perfect for use in imaging, diagnostics, tests for individual particles, and medication transportation frameworks. Ongoing advances in quantum dot design incorporate the potential for these nanocrystals to become therapeutic agents to restore numerous disease conditions themselves via bioconjugation with antibodies or medications. In this chapter, a few advances in the field of biomedical applications, such as bio-sensing, bio-imaging, drug loading capacity, targeted drug delivery, anti-stacking limit hostile to bacterial activity, photo-thermal treatment, photodynamic treatment, and optical properties for biomedical applications are presented, further to a short conversation on difficulties; for example, the biodistribution and harmful toxic effects of quantum dots is also discussed

Ternary Quantum Dots in Chemical Analysis. Synthesis and Detection Mechanisms

Ternary quantum dots (QDs) are novel nanomaterials that can be used in chemical analysis due their unique physicochemical and spectroscopic properties. These properties are size-dependent and can be adjusted in the synthetic protocol modifying the reaction medium, time, source of heat, and the ligand used for stabilization. In the last decade, several spectroscopic methods have been developed for the analysis of organic and inorganic analytes in biological, drug, environmental, and food samples, in which different sensing schemes have been applied using ternary quantum dots. This review addresses the different synthetic approaches of ternary quantum dots, the sensing mechanisms involved in the analyte detection, and the predominant areas in which these nanomaterials are usedThe authors give thanks to the CONACYT support for the grant number 771019S

Aptamer-Modified Semiconductor Quantum Dots for Biosensing Applications

Semiconductor quantum dots have attracted extensive interest in the biosensing area because of their properties, such as narrow and symmetric emission with tunable colors, high quantum yield, high stability and controllable morphology. The introduction of various reactive functional groups on the surface of semiconductor quantum dots allows one to conjugate a spectrum of ligands, antibodies, peptides, or nucleic acids for broader and smarter applications. Among these ligands, aptamers exhibit many advantages including small size, high chemical stability, simple synthesis with high batch-to-batch consistency and convenient modification. More importantly, it is easy to introduce nucleic acid amplification strategies and/or nanomaterials to improve the sensitivity of aptamer-based sensing systems. Therefore, the combination of semiconductor quantum dots and aptamers brings more opportunities in bioanalysis. Here we summarize recent advances on aptamer-functionalized semiconductor quantum dots in biosensing applications. Firstly, we discuss the properties and structure of semiconductor quantum dots and aptamers. Then, the applications of biosensors based on aptamer-modified semiconductor quantum dots by different signal transducing mechanisms, including optical, electrochemical and electrogenerated chemiluminescence approaches, is discussed. Finally, our perspectives on the challenges and opportunities in this promising field are provided

Aptamer-Modified Semiconductor Quantum Dots for Biosensing Applications

Semiconductor quantum dots have attracted extensive interest in the biosensing area because of their properties, such as narrow and symmetric emission with tunable colors, high quantum yield, high stability and controllable morphology. The introduction of various reactive functional groups on the surface of semiconductor quantum dots allows one to conjugate a spectrum of ligands, antibodies, peptides, or nucleic acids for broader and smarter applications. Among these ligands, aptamers exhibit many advantages including small size, high chemical stability, simple synthesis with high batch-to-batch consistency and convenient modification. More importantly, it is easy to introduce nucleic acid amplification strategies and/or nanomaterials to improve the sensitivity of aptamer-based sensing systems. Therefore, the combination of semiconductor quantum dots and aptamers brings more opportunities in bioanalysis. Here we summarize recent advances on aptamer-functionalized semiconductor quantum dots in biosensing applications. Firstly, we discuss the properties and structure of semiconductor quantum dots and aptamers. Then, the applications of biosensors based on aptamer-modified semiconductor quantum dots by different signal transducing mechanisms, including optical, electrochemical and electrogenerated chemiluminescence approaches, is discussed. Finally, our perspectives on the challenges and opportunities in this promising field are provided

Nanoparticules inorganiques luminescentes dopées aux lanthanides : synthèses, caractérisations et applications

Dans cette thèse, les nanoparticules d'oxysulfure et de fluorure de terres rares dopées au lanthanide sont explorées en tant que nanosondes pour des applications d'imagerie multimodale, de détection de température et d'imagerie temporelle. Le premier chapitre donne une brève introduction sur les nanoparticules susmentionnées et leurs propriétés optiques et leurs applications. Dans le chapitre 2, nous présentons une stratégie polyvalente pour la synthèse de 15 types de nanoparticules ultrapetites oxysulfure de terre rare (RE2O2S) d'une taille de 3 à 10 nm. Les NP Gd2O2S:Nd revêtues de PVP d'une taille de 6 nm sont synthétisées par une méthode d'échange de ligand. Nous démontrons que les NP Gd2O2S:Nd ultrapetites revêtues de PVP sont de bons agents de contraste en résonance magnétique pondérée (RM) T1 et T2, en tomodensitométrie (CT), en fluorescence dans le proche infrarouge (NIR-II) ainsi qu'en d'imagerie photoacoustique. Dans le chapitre 3, nous concevons une nouvelle hétérostructure cœur/coque dopé Ln3+. Des particules de Gd2O2S:20 %Yb,1%Tm ultra-petites (~ 5 nm) sont recouvertes d'une coque ß-NaYF4 optiquement inerte de ~ 4 nm par croissance épitaxiale, grâce au petit décalage de maille. Les nanoparticules à conversion ascendante Gd2O2S:20%Yb,1%Tm@NaYF4 core/shell UCNPs montrent une augmentation d'intensité de conversion ascendante de plus de 800 fois UCL par rapport à l'intensité du-coeur seul, une augmentation de durée de vie (transition 3H4 → 3H6 de Tm3+) de près de 1000 µs par rapport à 5 µs pour les cœur, et un rendement quantique de conversion ascendante jusqu'à 0,76 % à 155 W/cm2, ce qui est en concurrence avec d'autres UCNP à base de ß-NaYF4 avec des tailles similaires. Dans le chapitre 4, nous étudions le comportement thermique de la luminescence UC de nanoparticules Gd2O2S:20%Yb,1%Tm@NaYF4 et Gd2O2S:20%Yb,2%Er@NaYF4 cœur/coquille dans la plage de température de 293-473 K. Ensuite nous étudions comment la variation de la déformation du réseau influence le rapport de 4F9/2 → 4I15/2/4S3/2 → 4I15/2 de particules Gd2O2S:20%Yb,2%Er@NaYF4 avec une température variable. En outre, la sensibilité thermique relative record de 3,9% K-1 des particules Gd2O2S:20%Yb,1%Tm@NaYF4 est démontrée. Enfin, au chapitre 5, des objets cœur/coquille à conversion ascendante NaYF4:40%Gd,20%Yb,1%Tm@NaYF4:10%Yb@NaYF4:20%Nd,10%Yb sont synthétisés. Sur la base d'instruments optiques avancés, des spectres UCL à synchronisation temporelle et des durées de vie à 802 nm de Tm3+ sous une excitation laser de 808 nm sont mesurés, ce qui offre une possibilité théorique d'imagerie temporelle à l'aide des mêmes longueurs d'onde d'excitation et d'émission (~ 800 nm). Les conclusions et perspectives de ce travail sont explicitées dans le chapitre 6.In this thesis, lanthanide-doped rare earth oxysulfide and fluoride nanoparticles (NPs) are explored as nanoprobes for multimodal imaging, temperature sensing and time-gated imaging applications. The first chapter gives a brief introduction on the aforementioned nanoparticles and their optical properties and applications. In chapter 2, we present a versatile strategy for synthesis of 15 kinds of ultrasmall rare earth oxysulfide (RE2O2S) NPs with size of 3~10 nm. PVP-coated Gd2O2S:Nd NPs with size of 6 nm are synthesized through a ligand exchange method. We demonstrate that the ultrasmall PVP-coated Gd2O2S:Nd NPs are capable of T1 and T2 weighted magnetic resonance (MR), computed tomography (CT), second near infrared (NIR-II) fluorescence, photoacoustic, and ultrasound imaging. In chapter 3, we design a new Ln3+-doped core/shell heterostructure. ~5 nm ultrasmall Gd2O2S:20%Yb,1%Tm core is coated with ~4 nm optically inert ß-NaYF4 shell by epitaxial growth due to small lattice mismatch. The Gd2O2S:20%Yb,1%Tm@NaYF4 core/shell upconversion nanoparticles (UCNPs) show more than 800 times enhancement of upconversion luminescence (UCL) intensity compared to intensity of the core, lifetime (3H4 → 3H6 transition of Tm3+) of nearly 1000 µs compared to 5 µs of core, and upconversion quantum yield up to 0.76% at 155 W/cm2, which competes with other ß-NaYF4 based UCNPs with similar sizes. In chapter 4, we study UCL luminescence thermal enhancement behavior of Gd2O2S:20%Yb,1%Tm@NaYF4 and Gd2O2S:20%Yb,2%Er@NaYF4 core/shell UCNPs in the temperature range of 293-473 K. Then we further study how the variation of lattice strain influences the ratio of 4F9/2 → 4I15/2/4S3/2 → 4I15/2 of Gd2O2S:20%Yb,2%Er@NaYF4 core/shell UCNPs with varying temperature. Further, the highest relative thermal sensitivity of 3.9% K-1 of Gd2O2S:20%Yb,1%Tm@NaYF4 core/shell UCNPs is determined. In chapter 5, NaYF4:40%Gd,20%Yb,1%Tm@NaYF4:10%Yb@NaYF4:20%Nd,10%Yb core/shell/shell UCNPs are synthesized. Based on advanced optical instruments, time-gated UCL spectra and lifetimes at 802 nm of Tm3+ under 808 nm laser excitation are measured, which provide theoretical possibility for time-gated imaging using the same excitation and emission wavelengths (~800 nm). Conclusions and perspectives for this work are elucidated in chapter 6