Surface Of Quantum Dots Research Articles

Characterization of CdSe QDs biosynthesized by a recombinant Rhodopseudomonas palustris

This study proposed a novel approach for the biosynthesis of CdSe quantum dots (QDs) by a recombinant photosynthetic bacteria Rhodopseudomonas palustris with metallothionein expression. The biosynthesis mechanisms and physico-chemical properties of the CdSe QDs were analyzed by various techniques, and its potential application was also investigated. The results showed that the biosynthesized CdSe QDs presented green fluorescence with maximum excitation and emission wavelengths at 460 and 530 nm, respectively. The quantum yield of the biosynthesized CdSe QDs was found out to be 3.85%. They were well-dispersed spherical particles with an average size of 5.37 ± 0.06 nm. Their crystal structure was cubic with the d spacings of 3.1 Å and 2.5 Å, corresponded to the planes of (111) and (220), respectively. The biosynthesis process of CdSe QDs took place in the cytoplasm and may involve some proteins, peptides, lipids or other organic substances covering the surface of CdSe QDs through several specific functional groups, such as hydroxyl or sulfhydryl groups to maintain their stability. The purified CdSe QDs had good biocompatibility and great potential for cellular imaging application. It is concluded that the process may provide a more cost-effective and eco-friendly method not only to recover harmful cadmium in the environment but also to synthesize simultaneously a clean product for various industrial applications.

Application of thiol capped ZnS quantum dots as a fluorescence probe for determination of tetracycline residues

A new rapid and sensitive fluorescence probe based on zinc sulfide (ZnS) quantum dots (QDs) as an eco-friendly alternative has been produced for the detection of tetracycline (TCy). ZnS QDs have been innovatively prepared via simple aqueous colloidal method with thioglycolic acid (TGA) as a stabilizer and characterized by infrared spectroscopy, X-ray diffraction, transmission electron microscopiy, UV–Visible absorption and photoluminescence spectroscopy. The blue shift of the absorption band and bandgap values with respect to that of bulk ZnS materials confirms the quantum confinement effect. IR spectra show the binding of TGA to the surface of ZnS QDs. X-ray diffraction confirms the formation of a cubic phase of ZnS. Temperature-dependent photoluminescence (PL) spectroscopy shows three emission bands at 405 nm, 442 nm and 483 nm ascribed to electronic transitions involving Zn and S vacancies and interstitial sites. TGA-ZnS QDs is.able to detect TCy in an aqueous medium with a pH compatible with the pH of biological fluids which highlight the flexibility and applicability of this sensor in real media. Regarding TCy detection by QD fluorescence, a linear relationship of fluorescence intensity and TCy concentration is obtained over the wide range of 25–6000 nM, and the limit of detection (LOD) is as low as 0.03 nM. Thanks to its excellent analytical performance, such ZnS QDs fluorescent probe is a promising sensing platform for the analysis of trace TCy in biological fluids. Current probe was applied for TCy quantification in milk samples with superior results.

Colorimetric detection of heavy metal ions in potable water

Heavy metal ion is one of the most serious environmental problems that endanger the sustainability of the world's water supply. The development of practical sensors for ambient heavy metal monitoring has thus been the subject of various efforts. The sensitivity, selectivity, multiplexed detection capability, and portability of the colorimetric detector are all enhanced by the use of nanomaterials. This study discusses advances in biological and chemical-based colorimetric sensors for detecting heavy metal ions in drinkable water. Biological micromolecular dye-based and polymer dye-based detectors are also mentioned. In addition, chemical-based localized surface plasmon resonance (LSPR), quantum dots, and MOFs colorimetric detectors are discussed.

Bromide Decorated Eco‐Friendly ZnSeTe/ZnSe/ZnS Quantum Dots for Efficient Blue Light‐Emitting Diodes

AbstractMulti‐shelled ZnSeTe/ZnSe/ZnS quantum dots (QDs) have served as a promising eco‐friendly emitter for blue quantum dot light‐emitting diodes (QLEDs). While extensive studies have concentrated on the optimization of the shell species and thickness of the multi‐shelled QDs to raise the QLED electroluminescent performance, very few reports focus on the QD surface states involving ligand and defect modulations which are essential for high‐performance QLEDs. Herein, the strategy of bromide decoration is theoretically and practically demonstrated to simultaneously diminish the QD surface defects by passivating the unsaturated Zn for strengthened carrier radiative recombination and removing the superabundant oleic acid through ligand exchange for efficient carrier transport. As a result, the merits of bromide decoration benefit a large increase in photoluminescence quantum yield (PLQY) from 39.7% to 86.2% at the wavelength of 443 nm, as well as a great enhancement of the device performance with over sevenfold improvement in external quantum efficiency (EQE) from 0.74% to 5.46% and a distinct decrease in turn‐on voltage from 6.7 to 5.9 V. Consequently, this work contributes an effective approach of the multi‐shelled QD surface decoration toward enhanced QLED performance.

Quantum Dot loaded BQCA‐Octadecylamine conjugate nanosystems for theranostic applications in Alzheimer’s Disease.

AbstractBackgroundAlzheimer’s Disease (AD) is one of the most common types of dementias in the world and is characterized by progressive, irreversible neurodegeneration. Benzyl quinolone carboxylic acid was shown to have beneficial in management of AD. The current challenge with BQCA is its low brain half‐life, permeability and rapid elimination. The above challenge can be answered by formulating lipid drug conjugates of BQCA, with octadecyl amine (BQCA‐ODA). Quantum dots (QDs) with their unique optical properties, with high sensitivity and stability emerging as theranostic agents in several neurodegenerative diseases. Hypothesizing the co‐delivery of QDs and BQCA for the effective treatment of AD, in the present study we have formulated lipid nano carriers loaded with quantum dots (QDs) surface modified with Polysorbate 80, called PS80‐QD‐BQCA‐ODA‐NPs, for integrating imaging and therapy for effective management of AD.MethodBQCA was conjugated to Octadecyl amine (ODA), to form BQCA‐ODA LDC conjugate. The amphiphilic nature of the BQCA‐ODA conjugate allows the formation of self‐assembled nanoparticles. Here, we have employed solvent injection method followed by sonication, while addition of QDs in the organic phase and P80 in the aqueous phase to form PS80‐QD‐BQCA‐ODA‐NPs . The optimized formulation was evaluated for physicochemical properties (particle size, zeta potential and polydispersity index) surface morphology and in vitro drug release. The in vitro biocompatibility of the PS80‐QD‐BQCA‐ODA‐NPs was assessed on RBC and SHSY‐5Y cell lines. Further the application of PS80‐QD‐BQCA‐ODA‐NPs was assessed by in vivo imaging and behavioural studies on STZ induced mice models of AD.ResultThe formation of BQCA‐ODA conjugate formation was confirmed 13C‐NMR, 1H‐NMR, LC‐MS. The optimized PS80‐QD‐BQCA‐ODA‐NPs were found to have a near spherical shape with a particle size (PS) of 152.62 ± 1.82 nm, zeta potential (ZP) of 18.59 ± 0.56 mV and polydispersity index (PDI) of 0.214±0.08. PS80‐QD‐BQCA‐ODA‐NPs. The NPs shown improved brain permeability, with greater fluorescence intensity in mouse brains when compared to free QDs. In the in vivo efficiency studies PS80‐QD‐BQCA‐ODA‐NPs shown a significant improvement in memory in mice models.ConclusionThe PS80‐QD‐BQCA‐ODA‐NPs nanomedicine was successfully prepared, thoroughly characterized and has shown theronostic benefits in AD mice models.

Effects of Zn (II) on the Optical Properties of CdTe Quantum Dots and Their Photoluminescence Response to Lead Ion

Water-soluble CdTe quantum dots (QDs) have been utilized as photoluminescence probes for the detection of metal ions such as Pb2+, Hg2+, Cd2+, etc. We initially developed highly photoluminescence (PL) Zn-doped CdTe for toxic ions detection. A study on the changes of optical properties of Zn-doped CdTe and CdTe QDs when exposed to Pb2+ suggested that Pb2+ could act as a surface passivating agent to reduce Te2- dangling bonds while Zn2+ dopant stabilizes the QDs surface against ambient oxidation. The results demonstrated herein provide useful understandings of the interactions between water-soluble QDs and metal ions. These results suggest further applications of QDs in sensing metal ions.

Atomic layer deposition of diethylzinc/zinc oxide on InAs surface quantum dots: Self-clean-up and passivation processes

Passivation capping of molecular beam epitaxy (MBE)-grown InAs surface quantum dots (SQDs) is achieved by ex situ atomic layer deposition (ALD)-grown ZnO using diethylzinc (DEZ) as the zinc precursor, the main passivation agent, and oxygen plasma. Photoluminescence (PL) intensity is enhanced by 2-fold as the DEZ/ZnO passivation cap thickness reached 30 nm. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) show that contrary to conventional wet chemistry passivation or MBE capping, in which InAs SQDs can be damaged or be shrunken by intermixing of In and Ga, DEZ/ZnO passivation capping almost preserves the shape of the underlying SQDs. The cross-sectional analysis with transmission electron microscopy (TEM) reveals the formation of the ZnO grains on top of the sample accompanied by slight SQD height and width reduction, which are presumably related to the removal of the InAs native oxides. The DEZ “self-clean-up” passivation mechanism, where zinc precursor is responsible for reduction of the surface non-radiative recombination sites, is studied by X-ray photoelectron spectroscopy (XPS). The factors that control the DEZ “self-clean-up” efficiency such as the chain of chemical reactions, steric hindrance, decomposition activation energy, Gibbs reactivity, or Lewis acidity, are evaluated. The results are discussed in comparison with trimethylaluminum (TMA), a precursor used for Al2O3 deposition. We find that the “self-cleaning” by DEZ and TMA occurs through processes of different chemical nature.

Luminous Self-Assembled Fibers of Azopyridines and Quantum Dots Enabled by Synergy of Halogen Bond and Alkyl Chain Interactions

Herein, a simple approach for the fabrication of luminous self-assembled fibers based on halogen-bonded azopyridine complexes and oleic acid-modified quantum dots (QDs) is reported. The QDs uniformly align on the edge of the self-assembled fibers through the formation of van der Waals force between the alkyl chain of oleic acid on the QD surface and the alkyl chain of the halogen-bonded complexes, 15Br or 15I. Furthermore, the intermolecular interaction mechanism was elucidated by using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and density functional theory (DFT) calculations. This approach results in retention of the fluorescence properties of the QDs in the fibers. In addition, the bromine-bonded fibers can be assembled into tailored directional fibers upon evaporation of the solvent (tetrahydrofuran) when using capillaries via the capillary force. Interestingly, the mesogenic properties of the halogen-bonded complexes are preserved in the easily prepared halogen-bonded fluorescent fibers; this provides new insight into the design of functional self-assembly materials.

Reviving aged CsPbBr3 quantum dots by triallylamine etching

All-inorganic halide perovskite quantum dots are widely known to suffer luminescence degradation owing to their intrinsic instability in atmospheric circumstances. Their high surface energy and weak internal ionic bonding could result in quantum dot agglomeration and structural degradation. In this work, we demonstrate that triallylamine is an efficient recovery agent to reignite the luminescence emission of aged CsPbBr3 quantum dots. The aged CsPbBr3 quantum dots re-emit bright green light instantly after triallylamine etching. The X-ray photoelectron spectroscopy results indicate a noticeable decrease of surface under-coordinated Pb ions content, leading to surface re-healing and photoluminescence quantum yields increasing. The unique emission recovery could reveal the details of CsPbBr3 quantum dot surface variety and facilitate the development of perovskite quantum dot display devices.

Passivation and Interlayer Effect of Zr(i-PrO)4 on Green CuGaS2/ZnS/Zr(i-PrO)4@Al2O3 and Red CuInS2/ZnS/Zr(i-PrO)4@Al2O3 QD Hybrid Powders

Broadband emissive I–III–VI quantum dots (QDs) are synthesized as efficient and stable I–III–VI QDs to be used as eco-friendly luminescent materials in various applications. Here, we introduce the additional passivation of zirconium isopropoxide (Zr(i-PrO)4) to improve the optical properties and environmental stability of green-emitting CuGaS2/ZnS (G-CGS/ZnS) and red-emitting CuInS2/ZnS (R-CIS/ZnS) QDs. The photoluminescence quantum yield (PLQY) of both resultant Zr(i-PrO)4-coated G-CGS/ZnS and R-CIS/ZnS QDs reaches similar values of ~ 95%. In addition, the photostability and thermal-stability of G-CGS/ZnS/Zr(i-PrO)4 and R-CIS/ZnS/Zr(i-PrO)4 QDs are improved by reducing the ligand loss via encapsulation of the ligand-coated QD surface with Zr(i-PrO)4. It is also proved that the Zr(i-PrO)4-passivated interlayer mitigates the further degradation of I-III-V QDs from ligand loss even under harsh conditions during additional hydrolysis reaction of aluminum tri-sec-butoxide (Al(sec-BuO)3), forming easy-to-handle G-CGS/ZnS and R-CIS/ZnS QD-embedded Al2O3 powders. Therefore, the introduction of a Zr(i-PrO)4 complex layer potentially provides a strong interlayer to mitigate degradation of I–III–VI QD-embedded Al2O3 hybrid powders as well as passivation layer for protecting I–III–VI QD.

TiO2/CdS/CdSe quantum dots co-sensitized solar cell with the staggered-gap (type-II) heterojunctions for the enhanced photovoltaic performance

The effect of co-sensitization and ZnS passivation on the photovoltaic performance of CdS quantum dot sensitized solar cells (QDSSCs) were investigated. The deposition of CdS, CdSe quantum dots (QD) and ZnS passivation on TiO2 photoanode was carried out by successive ionic layer adsorption and reaction (SILAR) method. CdS/CdSe co-sensitization developed two staggered type-II heterojunctions at TiO2/CdS and CdS/CdSe interfaces and resulted a cascade energy band structure. This suitable band alignment facilitated the double charge transfer mechanism at each heterojunction and transported the electrons easily into the photoanode. The narrow bandgap sensitizers CdS and CdSe significantly improved the potential utilization of solar spectrum with more charge carrier generation. ZnS passivation on QD surface suppressed electrode/electrolyte interfacial charge recombination and facilitated more electron injection from QDs into TiO2 photoanode. The EDAX elemental mapping results inferred that CdS, CdSe and ZnS have efficiently covered the TiO2 surface. TiO2/CdS and CdS/CdSe interfaces and the amorphous nature of ZnS could be verified with HRTEM images. Hence, the co-sensitization and surface passivation played a significant role to enhance the PCE of CdS QDSSC from 1.9% to 4.05%.

The ammonia detection of cesium lead halide perovskite quantum dots in different halogen ratios at room temperature

Recently, all-inorganic perovskite structured nanomaterials CsPbX3 (X = Cl, Br, I or mixed halogen) quantum dots (QDs) have been developed rapidly in many applications such as photovoltaics, light-emitting diodes, and photoelectric detectors due to their excellent optical and photoelectrical properties. Meanwhile, this hot topic material also shows interesting potential in sensing applications because of the sensitive surface and large specific area. The reversible property in gas sensing makes it a promising material to realize highly sensitive visual gas sensor on the fluorescent signal. However, the influencing mechanism of the phenomenon gas molecules is still controversial in many situations. In this paper, we proposed a series of fluorescence turn-on ammonia gas sensors based on spin-coated CsPbX3 film. The wavelength of the fluorescent signal carrier was modulated by altering the ratio of halogen. By properly selecting the proportion of surface ligands and carefully analyzing the experiment results, we believe the dynamic passivation of ammonia molecule on the surface of perovskite QDs made dominated contribution to the sensing mechanism, and the series of CsPbX3 QDs sensor shared a similar trend at room temperature. In addition, the sensors we prepared exhibit impressive performance in sensitivity, response time, and reversibility, showing a good potential for low cost, high precision, miniaturized gas detection based on the optical signal.

Removal of Pb(II) from water samples using surface modified core/shell CdZnS/ZnS QDs as adsorbents: Characterization, adsorption, kinetic and thermodynamic studies

This research presents aqueous colloidal method to synthesize CdZnS/ZnS surface modified core/shell quantum dots (QDs) with capping agents 2-mercaptoacetic acid and 3-mercaptopropanoic acid. The QDs were characterized by the different analytical techniques. Using Plackett–Burman and Central composite designs, optimum conditions for the removal of Pb(II) from aqueous medium were developed: QDs (0.013 g) at pH 6.9, time of adsorption and desorption (20 min), temperature (61.1 °C) and dilution on 100 ppb standard solutions. Moreover, Freundlich models suggested that Pb(II) adsorption was favorable on the heterogeneous surface of QDs. The values of Δ G ° and Δ H ° (−59.26 KJ/mol.K) suggested the process was spontaneous and exothermic. The negative Δ S ° (−0.16 KJ/mol.K) indicates that the Pb(II) chemisorb on QDs. While, system follows the pseudo-second order rate equation which indicates that rate limiting step involves chemical reaction and could be influenced by the intraparticle/pore diffusion of Pb(II) ions with QDs. By using atomic absorption spectrophotometer, developed method was tested for Pb(II) removal from tap and ground water samples taken from the different districts of Karachi City. The % recovery for Pb(II) was found to be 96.4 % (tap water) and 94.8 % (ground water) with LOD = 0.1 ng mL −1 and LOQ = 0.90 ng mL −1 .

In Situ Bonding Regulation of Surface Ligands for Efficient and Stable FAPbI3 Quantum Dot Solar Cells.

Quantum dots (QDs) of formamidinium lead triiodide (FAPbI3 ) perovskite hold great potential, outperforming their inorganic counterparts in terms of phase stability and carrier lifetime, for high-performance solar cells. However, the highly dynamic nature of FAPbI3 QDs, which mainly originates from the proton exchange between oleic acid and oleylamine (OAm) surface ligands, is a key hurdle that impedes the fabrication of high-efficiency solar cells. To tackle such an issue, here, protonated-OAm in situ to strengthen the ligand binding at the surface of FAPbI3 QDs, which can effectively suppress the defect formation during QD synthesis and purification processes is selectively introduced. In addition, by forming a halide-rich surface environment, the ligand density in a broader range for FAPbI3 QDs without compromising their structural integrity, which significantly improves their optoelectronic properties can be modulated. As a result, the power conversion efficiency of FAPbI3 QD solar cells (QDSCs) is enhanced from 7.4% to 13.8%, a record for FAPbI3 QDSCs. Furthermore, the suppressed proton exchange and reduced surface defects in FAPbI3 QDs also enhance the stability of QDSCs, which retain 80% of the initial efficiency upon exposure to ambient air for 3000 hours.

Stable CsPbBr3 Achieved by Porphyrin–Thiol Surface Management and Their Dual‐Stimuli Responsive for Optical Encoding

AbstractSurface ligand management plays an essential role in improving the stability of perovskite quantum dots (QDs) and endowing them with novel property. Herein, a red fluorescence porphyrin‐thiol (named Por‐SH) is applied to adjust the surface and stimuli responsiveness of CsPbBr3 QDs. According to the theoretical and experimental results, Por‐SH can bind tightly to the exposed Pb of CsPbBr3 QDs, thus leading to the formation of Por‐SH‐QDs with an excellent resistance to water and UV light. Moreover, CsPbBr3 act as energy donors to improve the photoresponse of Por‐SH through energy transfer, especially when heated. Notably, the Por‐SH and QDs behave differently in terms of response to the temperature in the Por‐SH‐QDs system. Therefore, the Por‐SH‐QDs are capable of reversible stimuli–response property in the presence of heat/cool stimuli when excited by UV light. Finally, the disposable or reversible optical encoding label based on Por‐SH‐QDs and QDs is obtained by combining stability and the responsiveness to stimuli. Through the selection of suitable ligands, the surface of QDs is efficiently managed, which can not only mitigate instability but also endow perovskite QDs with the responsiveness to stimuli.

Theoretical Evaluation of Potential Cytotoxicity of Graphene Quantum Dot to Adsorbed DNA

As a zero-dimensional (0D) nanomaterial, graphene quantum dot (GQD) has a unique physical structure and electrochemical properties, which has been widely used in biomedical fields, such as bioimaging, biosensor, drug delivery, etc. Its biological safety and potential cytotoxicity to human and animal cells have become a growing concern in recent years. In particular, the potential DNA structure damage caused by GQD is of great importance but still obscure. In this study, molecular dynamics (MD) simulation was used to investigate the adsorption behavior and the structural changes of single-stranded (ssDNA) and double-stranded DNA (dsDNA) on the surfaces of GQDs with different sizes and oxidation. Our results showed that ssDNA can strongly adsorb and lay flat on the surface of GQDs and graphene oxide quantum dots (GOQDs), whereas dsDNA was preferentially oriented vertically on both surfaces. With the increase of GQDs size, more structural change of adsorbed ssDNA and dsDNA could be found, while the size effect of GOQD on the structure of ssDNA and dsDNA is not significant. These findings may help to improve the understanding of GQD biocompatibility and potential applications of GQD in the biomedical field.

Stabilizing dynamic surface of highly luminescent perovskite quantum dots for light-emitting diodes

Lead halide perovskite quantum dot (QD) shows great potential for application in light-emitting diodes (LEDs) due to its high photoluminescence quantum yield (PLQY), high exciton binding energy, tunable emission spectra and solution processibility. However, the dynamic binding of conventional organic acid/amine ligands to the QD surface significantly deteriorates its optoelectronic properties and stability, to a large extent affecting the electroluminescence performance of QD-based LEDs. Herein, the zwitterionic molecule, betaine (BET) that could firmly anchor on the QD surface, is introduced to stabilize the dynamic surface and simultaneously passivate the surface defects of QDs. Systematically experimental studies and theoretical calculations reveal that BET-treatment could remove the dynamically bonded OA/OAm ligands and substantially diminish the surface defects of QDs, leading to a boosted PLQY of up to 92 % with improved stability of BET-QDs. Consequently, the electroluminescence performance of green-emitting QD-LEDs was largely improved that the external quantum efficiency was increased to 10.8 %, along with a decreased turn-on voltage of 3.2 V. This work provides new insights into the design criterion of surface ligands for modulating the surface chemistry of perovskite QDs to realize high-performance LEDs or other optoelectronic devices.

Ligands for CsPbBr3 perovskite quantum dots: The stronger the better?

Surface ligands play important roles in synthesis, surface passivation, colloidal stability, and modulation of optoelectronic properties for quantum dots (QDs). It is well known that conventional ligands exhibit weak binding on the surface of perovskite QDs (PQDs), resulting in uncontrolled growth and unsatisfied stability during purification and operation. This impedes the device performance progress and practical applications severely. Stronger ligands anchoring on PQDs tightly and passivating surface defects efficiently have been reported to solve the problems. Herein, we choose a representative strong ligand, dodecylbenzene sulfonic acid (DBSA), to investigate its influence on PQD growth, stability under high-temperature with various solvents and additives, and the possibility of core–shell structure construction. Interestingly, the DBSA capped PQDs exhibit abnormally ripening under above conditions. Besides, a new mechanism for ion migration suppression is proposed based on internal lattice relaxation and inter-particle migration pathway elimination. Although DBSA-PQDs can be purified several times and maintain a high quantum yield, the corresponding light-emitting diodes show poor external quantum efficiency, which might be assigned to the unbalanced colloidal stability and film conductivity. This work indicates that strong ligands provide wider space for PQD modulation and the balance between stability and device performance should also be considered.

Acid-Base Reaction-Assisted Quantum Dot Patterning via Ligand Engineering and Photolithography.

The integration of quantum dots (QDs) into device arrays for high-resolution display and imaging sensor systems remains a significant challenge in research and industry because of issues associated with the QD patterning process. It is difficult for conventional patterning processes such as stamping, inkjet printing, and photolithography to employ QDs and fabricate high-resolution patterns without degrading the properties of QDs. Here, we introduce a novel strategy for the QD patterning process by treating QDs with a bifunctional ligand for acid-base reaction-assisted photolithography. Bifunctional ligands, such as MPA (mercaptopropionic acid) or TGA (thioglycolic acid), have a carboxyl group on one side that allows the QDs to be etched along with the photoresist (PR) by the base developer, while on the opposite side the ligands have a thiol group that passivates the QD surface. Passivating MPA ligands on QDs facilitates patterning of QD films and makes them compatible with harsh photolithography processes. We successfully achieved the patterning of QDs down to 5 μm. We also fabricated high-resolution patterned QD light-emitting diodes (LEDs) and QD photodetector arrays. Our patterning process provides precise control for the fabrication of highly integrated QD-based optoelectronic devices.

(Invited, Digital Presentation) Surface Engineering of Fluorescent CsPbBr3 and Carbon Quantum Dots By Perfluorocarboxylic Acid

CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) are an extremely attractive material with a narrow fluorescence peak and tunable emission color by halogen composition. Surface ligands have a variety of effects, including control of size and shape, uniform dispersion through good affinity with solvents and matrices, elimination of quenching sites due to surface defect capping effects and subsequent improvement of luminescent properties, and improvement of stability through surface protection. CsPbX3 QDs can be synthesized by hot injection and room temperature precipitation methods, using oleic acid (OA) and oleylamine (OLA) as surface ligands. One of the problems with these QDs is their low stability; the mechanism of degradation of QDs is the easy proton transfer between the carboxylate groups of OA and the ammonium groups of OLA on the surface of the QDs, resulting in the desorption of OA and OLA from the QD surface. Ligand desorption creates halogen vacancies, which act as trap levels that cause nonradiative recombination; therefore, it is important to design ligands that hardly desorb from the QD surface to suppress degradation of the QDs. In this talk, we will introduce our results on surface ligand of perfluorocarboxylic acid that improves thermal stability of CsPbBr3 QDs [1].Fluorescent carbon quantum dots (CQDs) are attracting attention as an alternative material to toxic QDs. In order to synthesize CQDs with a variety of fluorescent colors, it is effective to select aromatic compounds as carbon sources. The fluorescence color of CQDs changes depending on the polarity of the dispersant. This fluorescence solvatochromism is attributed to the change in the HOMO-LUMO energy gap of CQDs through the dipolar and hydrogen bonding interactions between CQDs and the dispersant molecules. In this talk, we will show that fluorescence solvatochromism of CQDs synthesized from p-phenylenediamine can be modulated by surface modification with perfluorocarboxylic acid [2].[1] D. Sato, Y. Iso, T. Isobe, ACS Omega, 5, 1178-1187 (2020).[2] K. Sato, R. Sato, Y. Iso, T. Isobe, Chem. Commun., 56, 2174-2177 (2020).