Functionalization of Cadmium Selenide Quantum Dots with Poly(ethylene glycol): Ligand Exchange, Surface Coverage, and Dispersion Stability

Wenger, Whitney; Bates, Frank S.; Aydil, Eray S.

doi:10.1021/acs.langmuir.7b01924

Cited by 36 publications

(27 citation statements)

References 34 publications

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“…PEG molecules present a zwitterionic character, which is also important for biological interactions. [14][15][16] Over the years, it was revealed that, besides the size-tunable emission, QDs present many other special features for biological application purposes: (i) broad absorption and narrow emission spectra, allowing the use of only one light source to obtain a multicolor labeling; (ii) high quantum yields, providing bright fluorescent images; (iii) low photobleaching rates allowing the follow-up of long-term real-time processes, and (iv) highly active surfaces for conjugations. 2,[17][18][19] In recent years, in vitro and in vivo QD biological applications have remarkably increased due to the outstanding physicochemical properties of these nanocrystals.…”

Section: Introductionmentioning

confidence: 99%

(Bio)conjugation Strategies Applied to Fluorescent Semiconductor Quantum Dots

Pereira¹,

Monteiro²,

Albuquerque³

et al. 2019

J. Braz. Chem. Soc.

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Quantum dots (QDs) are semiconductor nanocrystals, which present unique photophysical properties, enabling their application as new fluorescent platforms for biomedical sciences. Colloidal QDs are end-capped with organic or inorganic compounds, not only to prevent their agglomeration but also to provide reaction sites for the attachment of targeting (bio)molecules, nanoparticles or other interfaces, for specific biological purposes. The (bio)conjugation can involve non-covalent or covalent interactions, which can be accomplished through different strategies. The final assembly needs to maintain its chemical and optical stability and biochemical functionality. Although a relative good comprehension of the experimental procedures has been established, the bioconjugation process is still a challenge. The present manuscript aims to review the main (bio)conjugation strategies successfully applied to QDs, describing the steps necessary to prepare stable targeting fluorescent nanoplatforms, as well as some usual methods used to evaluate and optimize this process.

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Section: Introductionmentioning

confidence: 99%

(Bio)conjugation Strategies Applied to Fluorescent Semiconductor Quantum Dots

Pereira¹,

Monteiro²,

Albuquerque³

et al. 2019

J. Braz. Chem. Soc.

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“…For HS-PEG-NR, a second effect comes into play, which is the bulkiness of the PEG-moiety. This limits the number of surface ligands bound to the surface [60] and leads to an increasing ratio between electron traps due to undercoordinated Cd 2+ and hole traps induced by the thiolate group binding to the surface. This leads to a further decrease in Φ PL500.…”

Section: Photoluminescence Spectroscopymentioning

confidence: 99%

“…This introduces surface electron traps, ultimately changing the exciton recombination kinetics. For sub-2-nm CdSe QDs, it has been shown that less than 4 PEG molecules per QD adsorbed to the surface [60] (it has to be noted that the ligand exchange protocol differs from the one used in the report at hand). The longer lifetime, on the other hand, represents the exciton recombination dynamics similar to MUA-NR (with a similar k rad = 2.2 × 10 11 s −1 ).…”

Section: Photoluminescence Spectroscopymentioning

confidence: 99%

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Influence of Surface Ligands on Charge-Carrier Trapping and Relaxation in Water-Soluble CdSe@CdS Nanorods

2020

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In this study, the impact of the type of ligand at the surface of colloidal CdSe@CdS dot-in-rod nanostructures on the basic exciton relaxation and charge localization processes is closely examined. These systems have been introduced into the field of artificial photosynthesis as potent photosensitizers in assemblies for light driven hydrogen generation. Following photoinduced exciton generation, electrons can be transferred to catalytic reaction centers while holes localize into the CdSe seed, which can prevent charge recombination and lead to the formation of long-lived charge separation in assemblies containing catalytic reaction centers. These processes are in competition with trapping processes of charges at surface defect sites. The density and type of surface defects strongly depend on the type of ligand used. Here we report on a systematic steady-state and time-resolved spectroscopic investigation of the impact of the type of anchoring group (phosphine oxide, thiols, dithiols, amines) and the bulkiness of the ligand (alkyl chains vs. poly(ethylene glycol) (PEG)) to unravel trapping pathways and localization efficiencies. We show that the introduction of the widely used thiol ligands leads to an increase of hole traps at the surface compared to trioctylphosphine oxide (TOPO) capped rods, which prevent hole localization in the CdSe core. On the other hand, steric restrictions, e.g., in dithiolates or with bulky side chains (PEG), decrease the surface coverage, and increase the density of electron trap states, impacting the recombination dynamics at the ns timescale. The amines in poly(ethylene imine) (PEI) on the other hand can saturate and remove surface traps to a wide extent. Implications for catalysis are discussed.

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“…To exchange ligands on the surface of NPs, the concentration and surface affinity of the new molecules should be higher than the concentration and affinity of the original ligand (Karakoti et al 2015). The ligands often used for surface modification to obtain hydrophilic, non-aggregating NPs include polymers (e.g., polyethylene glycol (Liu and Luo 2014;Wenger et al 2017)), amines, phosphines, or compounds containing thiol groups (Lee et al 2010) (such as 3-mercaptopropionic acid and its derivatives (Liu and Luo 2014), glutathione (Wang et al 2012), dihydrolipoic acid (La Rosa et al 2017)).…”

Section: Introductionmentioning

confidence: 99%

Surface modification of cadmium-based nanoparticles with d-penicillamine—study of pH influence on ligand exchange reaction

et al. 2020

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Semiconducting nanoparticles (NPs) find applications in many fields, with a recent focus on medicine and biology. Functionalization of the surface of NPs is necessary, and one of the most commonly employed techniques is ligand exchange (LE). In this paper, the study of pH influence on LE reaction for different types of cadmium-based NPs (quantum dots, nanorods, and nanoplates) is presented. Hydrophobic NPs were transferred to the nonorganic medium by functionalization with D-penicillamine (DPA). The LE procedure was conducted at four different pH levels (4, 7, 9, and 11), and obtained hydrophilic NPs were dispersed in phosphate buffer. Results show that the most effective procedure resulted from a reaction carried at pH = 4; however, NPs with higher photoluminescence intensity were obtained when pH = 11 was used. Comparable emission was achieved from samples at pH = 4 and pH = 9. The least effective transfer, resulting in unstable NPs, occurred when the procedure was conducted at pH = 7.

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Functionalization of Cadmium Selenide Quantum Dots with Poly(ethylene glycol): Ligand Exchange, Surface Coverage, and Dispersion Stability

Cited by 36 publications

References 34 publications

(Bio)conjugation Strategies Applied to Fluorescent Semiconductor Quantum Dots

(Bio)conjugation Strategies Applied to Fluorescent Semiconductor Quantum Dots

Influence of Surface Ligands on Charge-Carrier Trapping and Relaxation in Water-Soluble CdSe@CdS Nanorods

Surface modification of cadmium-based nanoparticles with d-penicillamine—study of pH influence on ligand exchange reaction

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