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We report a simple and versatile method for effectively replacing the toxic ligands, such as cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC), on the surface of Au nanospheres with different sizes by citrate. The method involves the deposition of an ultrathin shell of fresh Au in the presence of sodium citrate at an adequate concentration. After the ligand exchange process, multiple techniques are used to confirm that the surface of the resultant Au nanospheres is covered by citrate while there is no sign of aggregation. We also demonstrate the mitigation of cell toxicity after exchanging the surface‐bound CTAB/CTAC with citrate, opening the door to a range of biomedical applications. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskite quantum dots (QDs) have garnered significant research interest owing to their unique structure and optoelectronic properties. However, their poor optical performance in ambient air remains a significant limitation, hindering their advancement and practical applications. Herein, three amino acids (valine, threonine and cysteine) were chosen as surface ligands to successfully prepare highly luminescent CH3NH3PbBr3 (MAPbBr3) QDs. The morphology and XRD results suggest that the inclusion of the amino acid ligands enhances the octahedral structure of the QD solutions. Moreover, the observed blue-shifted phenomenon in the photoluminescence (PL) aligns closely with the blue-shifted phenomenon observed in the ultraviolet–visible (UV-Vis) absorption spectra, attributed to the quantum confinement effect. The time-resolved spectra indicated that the introduction of the amino acid ligands successfully suppressed non-radiative recombination, consequently extending the fluorescence lifetime of the MAPbBr3 QDs. The photoluminescence quantum yields (PLQYs) of the amino acid-treated MAPbBr3 QDs are increased by 94.8%. The color rendering index (CRI) of the produced white light-emitting diode (WLED) is 85.3, with a correlated color temperature (CCT) of 5453 K. Our study presents a novel approach to enhancing the performance of perovskite QDs by employing specially designed surface ligands for surface passivation. [ABSTRACT FROM AUTHOR]

Surface ligands play an important role in shape‐controlled growth and stabilization of colloidal nanocrystals. Their quick removal tends to cause structural deformation and/or aggregation to the nanocrystals. Herein, we demonstrate that the surface ligand based on poly(vinylpyrrolidone) (PVP) can be slowly removed from Pd nanosheets (NSs, 0.93±0.17 nm in thickness) by simply aging the colloidal suspension. The aged Pd NSs show well‐preserved morphology, together with significantly enhanced stability toward both e‐beam irradiation and electrocatalysis (e.g. ethanol oxidation). It is revealed that the slow desorption of PVP during aging forces the re‐exposed Pd atoms to reorganize, facilitating the surface to transform from being nearly perfect to defect‐rich. The resultant Pd NSs with abundant defects no longer rely on surface ligand to stabilize the atomic arrangement and thus show excellent structural and electrochemical stability. This work provides a facile and effective method to maintain the integrity of colloidal nanocrystals by slowly removing the surface ligand. [ABSTRACT FROM AUTHOR]

Metal organic frameworks derived NiCo hydroxides with abundant Ni3+ species and surface oxalate ligand are synthesized for highly enhanced electrochemical glycerol oxidation reaction. [Display omitted] Glycerol oxidation reaction can be substituted for oxygen evolution reaction for more efficient hydrogen production due to its lower thermodynamic potential. Herein, a series of NiCo hydroxide nanosheets containing abundant Ni3+ species and surface ligands were synthesized by in - situ structural transformation of bimetallic organic frameworks in alkaline media for efficient glycerol oxidation reaction. It is found that the incorporation of Co ions increases the content of the Ni3+ species, and that the Ni/Co ratio of 1.0 lead to the optimal catalytic performance. The oxalate-modified nickel–cobalt hydroxide with the optimized Ni/Co ratio can deliver a current density of 10 mA cm−2 at 1.26 V vs. RHE (reversible hydrogen electrode), and reaches its maximum selectivity and Faradaic efficiency at 1.30 V vs. RHE. A high selectivity of 82.9% and a Faradaic efficiency of 91.0% are achieved. The high catalytic activity can be mainly attributed to the abundant Ni3+ species and surface carboxyl groups. [ABSTRACT FROM AUTHOR]

The role of surface ligand in tuning the carrier dynamics of reverse type I Al0.3Ga0.7As/ GaAs Core/Shell Nanostructure (CSN) has been investigated by considering two different ligand matrices: (i) inorganic 2D SiO2 and (ii) organic 2D conjugated polymer (2D-CP) with barrier potentials of 3.9 eV and 0.784 eV, respectively. The effective mass approximation combined with the variation technique is used to calculate the numerical results. The impact of ligand on the binding energy (BE) and diamagnetic susceptibility (χdia) of donor is examined for various donor locations (R) at varied core (Rc) and shell (Rs) radii. The spatial extent of carriers (red2) manifests the tunneling ability of electrons in the CSNs. The system exhibits diverse behavior and increased stability in the presence of organic 2D-CP and inorganic 2D SiO2 matrix. The present work will update the significance of ligand passivated reverse type I CSN for effective quantum tunneling devices. [ABSTRACT FROM AUTHOR]

The structure determination of metal nanoclusters protected by ligands is critical in understanding their physical and chemical properties, yet it remains elusive how the metal core and ligand of metal clusters cooperatively contribute to the observed performances. Here, with the successful synthesis of Au44TBPA22Cl2 cluster (TBPA = 4-tert-butylphenylacetylene), the structural isomer of previously reported Au44L28 clusters (L denoted as ligand) is filled, thereby providing an opportunity to explore the property evolution rules imparted by different metal core structures or different surface ligands. Time-resolved transient absorption spectroscopy reveals that the difference in the core structure between Au44TBPA22Cl2 and Au44L28 can bring nearly 360 times variation of excited-state lifetime, while only 3–24 times differences in excited-state lifetimes of the three Au44L28 nanoclusters with identical metal core but different ligands are observed, which is due to much stronger impact of the metal core than the surface ligands in the electronic energy bands of the clusters. In addition, the Au44 clusters protected by alkyne ligands are shown to be highly effective toward the electrochemical oxidation of ethanol, compared to the Au44 clusters capped by thiolates, which is ascribed to smaller charge transfer impedance of the former clusters. We anticipate that the study will enhance the process in controlling the nanomaterial properties by precisely tailoring metal core or surface patterns. [ABSTRACT FROM AUTHOR]

Water-soluble Mn2+ doped CsPbCl 3 nanocrystals coating by 6-aminocaproic acid (ACA) ligand were prepared by a simple ligand assisted reprecipitation method at room temperature. The CsPbCl 3 :Mn2+/ACA nanocrystals were almost cubic phase and had mean size of about 10 nm. Due to the coating and passivation of ACA, the CsPbCl 3 :Mn2+/ACA nanocrystals retained the initial fluorescence intensity of 20% after being dispersed in deionized water for 20 days. The orange LED device based on CsPbCl 3 :Mn2+/ACA nanocrystals were prepared with excellent luminescence properties. In the cytotoxicity test, even if the MCF-7 cells were cultured for 24 h at the concentration of CsPbCl 3 :Mn2+/ACA nanocrystals as high as 160 μg·ml−1, the cell survival rate was still 70%. Confocal fluorescent cell imaging results showed that the nanocrystals had remarkable fluorescent cell imaging effect even after 24 h. The synthesized CsPbCl 3 :Mn2+/ACA nanocrystals have nice water solubility, good water stability, low cytotoxicity and highly luminescence properties, and have great application potential in the field of orange LED and fluorescent probes. [ABSTRACT FROM AUTHOR]

Inorganic metal halide perovskites have very promising applications in light-emitting diodes (LED), solar cells, lasers, and photodetectors owing to their outstanding optoelectronic characteristics. However, halide segregation is quite a challenge in the industrialization process of pure red perovskite LEDs with stable emission. In this work, we addressed this issue by doping with KBr in the nucleation of nanocrystals (NCs) and postmodifying with quaternary ammoniums (e.g., tetrabutylammonium bromide, TBAB). Mixed halide perovskite NCs (CsPbI3–xBrx NCs) with excellent optical performances and stabilities were obtained. The emission maximum was at ∼636 nm, and the full-width-at-half-maximum (fwhm) was 28 nm, achieving the requirement of Rec. 2020. The solution and film of KBr/TBAB-CsPbI3–xBrx NCs could keep pure red emission after exposure in the air for 65 and 90 days, respectively. The photoluminescence quantum yield (PLQY) of the KBr/TBAB-CsPbI3–xBrx NCs solution remained 90% and the emission peak had only a very slight shift after 240 h of irradiation at 365 nm. This study demonstrated an efficient route for highly stable pure red perovskite NCs and highlighted the critical role of surface ligands, which is expected to be applied in the future. [ABSTRACT FROM AUTHOR]

Nanoplastics, as emerging contaminants, have been causing great panic, potentially affecting human health in recent years. Some in vitro studies have indicated that nanoplastics may induce severe toxicity. However, the mechanisms underlying this potential toxicity are insufficiently understood. In this study, we have found PS-NH 2 nanoplastics had the obvious DNA cleavage activities, while PS-COOH nanoplastics were not observed to have the DNA cleavage abilities. Both microsized PS-NH 2 and PS-COOH microplastics lacked DNA cleavage activities, indicating the importance of size and surface ligand in nanoplastics' DNA cleavage. The DNA cleavage system by nanoplastics remains stable under varying pH and temperature. From the mechanism exploration, the interaction energy is much higher between PS-NH 2 nanoplastics than PS-COOH nanoplastics, further illuminating that PS-NH 2 nanoplastics have stronger binding interaction with DNA to induce DNA cleavage activities. This study offers insights into the potential environmental risks and toxicity of nanoplastics in the aquatic ecosystems.

CsPbI 3 perovskite quantum dots (PQDs) have emerged as promising photovoltaic materials for third-generation solar cells, owing to their superior optoelectronic properties. Nevertheless, the performance of CsPbI 3 PQD solar cells is primarily hindered by low carrier extraction efficiency, largely due to the insulative ligands. In this study, we introduced a semiconductor molecule, [6,6]-phenyl C 61 butyric acid methyl ester (PCBM), onto the surfaces of CsPbI 3 PQDs as surface ligands to enhance photogenerated charge extraction. The results indicate that PCBM accelerates carrier separation in CsPbI 3 PQDs by forming a type II heterojunction, and also modulates the energy level of CsPbI 3 PQDs by altering surface dipole moments. Additionally, we established an energy-level gradient alignment in the PCBM/CsPbI 3 PQD heterojunction absorber layer, which was found to effectively promote carrier extraction and reduce carrier recombination loss in PQD solar cells. Ultimately, the PQD solar cells incorporating this novel structure achieved a power conversion efficiency of 14.23%, a significant improvement compared to 12.69% achieved by solar cells with a traditional structure, thus demonstrating the strong potential of this approach for high-performance PQD solar cells.

Comprehensive Summary: The self‐assembled metal halide perovskite (MHP) nanocrystal superlattices have attracted many researchers due to their exceptional optical and electrical properties. The bottom‐up self‐assembly can be facile to generate ideal and periodic structures. The superlattices' stability can be improved and the photoluminescence lifetime can be extended by an order of magnitude. However, due to lack of a comprehensive and systematic understanding of the internal interactions on self‐assembled processes now, superlattices cannot be obtained controllably and play full use of their advantages. Therefore, gaining a deep insight of interaction forces about self‐assemblies is the premise of designing and controlling the degree of self‐assembly so as to prepare ideal materials. In this review, the definitions and functions of driving forces including van der Waals forces, electrostatic interactions and hydrogen bonds are discussed. Subsequently, we aim to explore the dominant factors affecting the driving forces, which can make a difference in the process of MHP self‐assembly. Based on current researches, we emphasize on three aspects−the core of nanocrystals, surface ligands and solvents−to clarify their critical roles in controlling the driving forces. Finally, the outlooks and perspectives of how to facilitate the MHP self‐assembly and their application on blue light emitting diodes are discussed. [ABSTRACT FROM AUTHOR]

Surface ligands of colloidal quantum dots (QDs) have a profound influence on their surface states, which has been verified in the studies of the effect of ligand head groups on the photoluminescence (PL) properties of QDs. However, the investigation of the ligand chain length is limited. Here, we systematically explored the effect of chain length on the Ag2Se QDs by selecting three ligands, 1-octanethiol (OTT), 1-dodecanethiol (DDT), and 1-hexadecanethiol (HDT), with diverse chain lengths. We found that the PL intensity of Ag2Se QDs increased with the decrease of the ligand chain length due to the enhanced passivation of surface defects emerging from the robust QD-ligand interface binding affinity and the weaker hydrophobic chain—chain interaction. Subsequently, AgAuSe QDs terminated with OTT were obtained by alloying parent OTT-Ag2Se QDs with Au precursor with a record absolute PL quantum yield (PLQY) of 87.2% at 970 nm, facilitating ultrasensitive in vivo angiography imaging in a nude mouse model. We expect that our finding of the important role of the ligand chain length on the optical properties of QDs will be suggestive to the design and synthesis of high-quality QDs, and also look forward to the clinical applications of the ultra-bright AgAuSe QDs. [ABSTRACT FROM AUTHOR]

Understanding of the atomic structure and stability of nanowires (NWs) is critical for their applications in nanotechnology, especially when the diameter of NWs reduces to ultrathin scale (1-2 nm). Here, using aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), we report a detailed atomic structure study of the ultrathin Au NWs, which are synthesized using a silane-mediated approach. The NWs contain large amounts of generalized stacking fault defects. These defects evolve upon sustained electron exposure, and simultaneously the NWs undergo necking and breaking. Quantitative strain analysis reveals the key role of strain in the breakdown process. Besides, ligand-like morphology is observed at the surface of the NWs, indicating the possibility of using AC-HRTEM for surface ligand imaging. Moreover, the coalescence dynamic of ultrathin Au NWs is demonstrated by in situ observations. This work provides a comprehensive understanding of the structure of ultrathin metal NWs at atomic-scale and could have important implications for their applications.

We examined systematically how self-assembled monolayers (SAMs) of different mercaptoacids affect the spectral shift of the localized surface plasmon resonance in silver nanoplates and nanospheres. We observed a clear trend in the magnitude of a redshift with a molecular length or the SAM thickness within a homologous series of aliphatic mercaptoacids: the thicker shell the stronger the red shift. Using classic Mie theory for plasmonic core-dielectric shell spheres and oblate spheroids we developed the method for determination of a pseudo-refractive index in SAM of different molecules and obtained a good correlation with the reference refractive indices for bulk long-chain aliphatic acids, but only in case of silver nanoplates. Calculations for silver core–shell nanospheres gave overestimated values of refractive index perhaps due to restrictions of Mie theory on the minimum particle size. [ABSTRACT FROM AUTHOR]

Photodegraded CsPbBr3 perovskite nanocrystals (NCs) can exhibit complete self-recovery following storage in the dark. This behavior results from the readsorption of surface ligands that experienced photoinduced desorption under UV light excitation. In the present work, mixed-halide CsPb-(Cl0.4Br0.6)3, CsPb-(Cl0.2Br0.8)3, and CsPb-(Br0.7I0.3)3 NCs were prepared via ion exchange to evaluate the influence of halide composition on the photodegradation and self-recovery of NCs. Partially substituting Cl– for Br– enhanced the photoactivation, which improved the photoluminescence properties by optimizing the adsorption state of the surface ligands during light excitation. In contrast, partially substituting I– for Br– reduced the stability of the cubic crystal structure, thus subjecting the NCs to irreversible degradation (likely including a partial phase transition) and preventing their self-recovery. Cycle tests confirmed the reversibility of the photodegradation/self-recovery of CsPbBr3 NCs; however, this behavior was disturbed by irreversible surface oxidation reactions when the sample was exposed to ambient air. Therefore, it was concluded that ambient air must be excluded to effectively take advantage of the self-recovery phenomenon for practical applications. [ABSTRACT FROM AUTHOR]

Functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are of increasing relevance for many key technologies of the twenty-first century. This includes polymer and silica or silica-coated nanoparticles (NP) with covalently bound surface groups, semiconductor quantum dots (QD), metal and metal oxide NP, and lanthanide-based NP with coordinatively or electrostatically bound ligands, as well as surface-coated nanostructures like micellar encapsulated NP. The surface chemistry can significantly affect the physicochemical properties of NM, their charge, their processability and performance, as well as their impact on human health and the environment. Thus, analytical methods for the characterization of NM surface chemistry regarding chemical identification, quantification, and accessibility of functional groups (FG) and surface ligands bearing such FG are of increasing importance for quality control of NM synthesis up to nanosafety. Here, we provide an overview of analytical methods for FG analysis and quantification with special emphasis on bioanalytically relevant FG broadly utilized for the covalent attachment of biomolecules like proteins, peptides, and oligonucleotides and address method- and material-related challenges and limitations. Analytical techniques reviewed include electrochemical titration methods, optical assays, nuclear magnetic resonance and vibrational spectroscopy, as well as X-ray based and thermal analysis methods, covering the last 5–10 years. Criteria for method classification and evaluation include the need for a signal-generating label, provision of either the total or derivatizable number of FG, need for expensive instrumentation, and suitability for process and production control during NM synthesis and functionalization. [ABSTRACT FROM AUTHOR]

The past decade has witnessed the increasing interest in cesium lead halide perovskite quantum dots (PQDs) for their excellent optical properties with higher photoluminescence efficiency and tunable emission wavelengths widely applied in white LED, photovoltaic devices, etc. Here we report the preparation of CsPbBr3 PQDs by a facile anti‐solvent method using conventional quaternary ammonium bromide (CTAB) as a double modifier—both proper alkyl group protection and bromine source donator. The as‐formed PQDs are well‐monodispersed cubes with a size of 10–15 nm and high photoluminescence quantum yield (PLQY) of up to 43 %. To enhance the stability of PQDs, CsPbBr3@PS microspheres were formed by electrospraying process. The microspheres not only show excellent luminous properties, but exhibit much higher stability against air and UV light irradiation due to the super hydrophobic property of polystyrene. [ABSTRACT FROM AUTHOR]

Analytical ultracentrifugation (AUC) is a powerful technique to observe colloidal nanocrystals (NCs) directly in solution and obtain critical information about their physical-chemical properties. Nevertheless, a more comprehensive implementation of AUC for the characterisation of such a class of crystalline colloids has been traditionally impaired by the requirement of having a priori knowledge of the complex, multilayered structure formed by NC in solution. This includes the nature (density and mass) of the surface ligands (SLs) that provide NC colloidal stability and the shell of solvent molecules formed on it. Herein, we propose a methodology to determine the NCs size by using SLs with a density equal to that of the solvent. Thereby, the buoyancy force of the SL shell is neutral, and the density of the NCs is sufficient a priori knowledge to calculate their related mass and size distributions. The simplicity and reliability of the method are evaluated with cetyltrimethylammonium bromide (CTAB) stabilized spherical gold NCs (AuNCs) of dimensions ranging from 1 to 17 nm. The proposed method has great potential to be transferred to any non-crystalline and crystalline colloids of different nature and composition, which have a density that is equal to the bulk and can be stabilized by SLs having a density that matches that of the solvent.

Silica-coated perovskite quantum dots (QDs), which exhibit exceptional photophysical properties, hold great promise for various optoelectronic applications. Nonetheless, the issue of insufficient stability poses a significant challenge to their continued advancement and widespread adoption. Herein, we present a novel approach for the synthesis of silica-coated CH 3 NH 3 PbBr 3 (CH 3 NH 3 = MA) QDs with exceptional stability and luminescence, which utilized hydrophobic ionic liquids (ILs) with unlike alkyl chain lengths as surface ligands. As the alkyl chain length of the hydrophobic ILs increased, we observed a blue-shift in the wavelength and a reduction in the time required to reach maximum fluorescence for the silica-coated perovskite QDs. It not only effectively prevents QD aggregation but also accelerates the formation rate of the SiO 2 shell. The introduction of ILs generated the enhancement of photoluminescence quantum yield (PLQY) from 85% for the pristine sample to 92.83% for ILs treated C 16 -QDs@SiO 2. Furthermore, the stability of the ILs-treated C 16 -QDs@SiO 2 was notably enhanced, with the fluorescence intensity retaining 80.5% after 40 days of storage. The as-prepared white light emitting diode (LED) displayed a high color rendering index (CRI) of 75.3 and a correlated color temperature (CCT) of 7529 K. This work provides an alternative strategy to solve the challenging stability issue of silica-coated perovskite QDs and promote the silica-coated perovskite QDs to the practical application in solid-state LEDs. [Display omitted] • The superior silica-coated perovskite QDs are based on exchanging of hydrophobic ionic liquids (ILs). • ILs ligands could avoid aggregation of QDs and accelerated the formation rate of SiO 2 shell. • ILs-treatment endows silica-coated perovskite QDs with a boosted PLQY of up to 92.83% with enhanced environmental stability. • The LED presents high color rendering index (CRI) of 75.3 and a correlated color temperature (CCT) of 7529 K. [ABSTRACT FROM AUTHOR]

With a stacking-layered architecture, the bilayer two-dimensional-three-dimensional (2D-3D) perovskite heterostructure (PHS) not only eliminates surface defects but also protects the 3D perovskite matrix from external stimuli. However, these bilayer 2D-3D PHSs suffer from impaired interfacial charge carrier transport due to the relatively insulating 2D perovskite fragments with a random phase distribution. Over the past decade, substantial efforts have been devoted to pioneering molecular and structural designs of the 2D perovskite interlayers for improving their charge carrier mobility, which enables state-of-the-art perovskite solar cells with high power conversion efficiency and exceptional operational stability. Herein, this review offers a comprehensive and up-to-date overview on the recent progress of bilayer 2D-3D PHSs, encompassing advancements on spacer cation engineering, interfacial charge carrier modification, advanced deposition protocols, and characterization techniques. Then, the evolutionary trajectory of bilayer 2D-3D PHSs is outlined by summarizing its mainstream development trends, followed by a perspective discussion about its future research opportunities toward efficient and durable perovskite solar cells.

Fluorescent silicon nanoparticles (SiNPs) bring exciting opportunities for long-awaited silicon-based optical application, while intrinsic indirect band gap of silicon severely limits photoluminescent quantum yield (PLQY) of SiNPs. To address this critical issue, we herein demonstrate a facile and general method, i.e., solvent polarity-induced photoluminescence enhancement (SPIPE), yielding several-fold increase in quantum yield (QY) of SiNPs. Typically, different kinds of 4-substituented-1,8-naphthalic anhydride molecules, i.e., 4-Br-1,8-naphthalic anhydride (BNA), 4-triphenylamino-1,8-naphthalic anhydride (TPNA), and 4-dimethylamino-1,8-naphthalic anhydride (DMNA), are rationally designed and synthesized, which serve as surface ligands for the production of BNA-, TPNA-, and DMNA-capped small-sized (diameter: ~ 3.8-5.8 nm) SiNPs with QY of ~ 8%, ~ 15%, ~ 16%, respectively. Of particular significance, QY of the resultant SiNPs could be greatly enhanced from ~ 10% to ~ 50% through the SPIPE strategy. Taken together with the theoretical calculation and the results of time-correlated single photon counting, we reveal that actived excited-state charge transfer interactions between surface-covered ligand and silicon oxide coating would be responsible for the observed QY enhancement. Moreover, other five kinds of solvents (i.e., methanol, isopropanol, dimethyl sulfoxide, N,N-dimethylformamide, and acetonitrile) are further employed for the SiNPs treatment, and similar improvement of QY values are observed, convincingly demonstrating the universal evidence of SPIPE of the SiNPs. [ABSTRACT FROM AUTHOR]

Water-soluble CdTe quantum dots are synthesized to investigate how short-chain surface ligands bearing -SH, -COOH, and -NH2 groups interact with CdTe during nucleation/growth processes. Their optical properties and colloidal stability after the ligand exchange are also investigated. We then characterize the resulting CdTe by fluorescence, UV–Vis absorption, and infrared spectroscopies. The stability of the colloidal dispersions was determined by their Zeta potentials. The results show that in the synthesis of water-soluble CdTe, surface ligands with at least two functional groups are required and the hard/soft character of them is an important factor in the stability of CdTe.

To investigate the thermal stabilities of CdSe and Cd-free quantum dots (QDs) in QD–silicone polymer nanocomposites, we synthesized both CdSe and CuInS 2 (CIS) QDs capped with different surface ligands (oleic acid (OA) and 1-dodecanethiol (1-DDT)). A comparison of the quantum yields of dried QDs after exposure to different temperatures revealed that the CIS QDs and 1-DDT ligands exhibited higher thermal stabilities than the CdSe QDs and OA ligands, respectively. We also prepared QD–silicone nanocomposites containing different types of QDs by varying the curing temperature and time and observed that nanocomposites containing CdSe QDs exhibited discoloration at high temperatures, whereas those containing CIS QDs did not. Moreover, the highest quantum efficiency (QE) of the QD–silicone nanocomposites was observed in the case of CIS QDs capped with 1-DDT and the lowest was observed in the case of CdSe QDs capped with OA. Because the dispersion states of QDs were not substantially affected at high temperatures, we attributed the high QE of nanocomposites containing the CIS QDs capped with 1-DDT to the superior thermal stability of CIS QDs and their surface ligand (i.e., 1-DDT). [ABSTRACT FROM AUTHOR]

Understanding of the atomic structure and stability of nanowires (NWs) is critical for their applications in nanotechnology, especially when the diameter of NWs reduces to ultrathin scale (1-2 nm). Here, using aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), we report a detailed atomic structure study of the ultrathin Au NWs, which are synthesized using a silane-mediated approach. The NWs contain large amounts of generalized stacking fault defects. These defects evolve upon sustained electron exposure, and simultaneously the NWs undergo necking and breaking. Quantitative strain analysis reveals the key role of strain in the breakdown process. Besides, ligand-like morphology is observed at the surface of the NWs, indicating the possibility of using AC-HRTEM for surface ligand imaging. Moreover, the coalescence dynamic of ultrathin Au NWs is demonstrated by in situ observations. This work provides a comprehensive understanding of the structure of ultrathin metal NWs at atomic-scale and could have important implications for their applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The growth kinetic process of Au@Cu 2 O nanostructures is controlled by employing three different surface ligands. • The morphologies of Au@Cu 2 O nanostructures are modulated by using different surface ligands. • The stability of Au@Cu 2 O core-shell NPs is in the following order: Au@Cu 2 O-PAA > Au@Cu 2 O-CTAB > Au@Cu 2 O-SDS. Cu 2 O nanoparticles, as a visible-light responsive p-type semiconductor, have attracted much attention in photocatalysis. However, the applications of Cu 2 O NPs have been limited due to the low transferring efficiency of photogenerated charge carriers. In this study, taking Au nanorods as core, the growth kinetic process, morphology, and stability of Au@Cu 2 O nanostructures were controlled by employing three different surface ligands, namely, polyacrylic acid (PAA), cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). As a result, relatively stable Au@Cu 2 O nanocubes were obtained using CTAB. Au@Cu 2 O NPs with cubic morphology can also be observed using anionic SDS. However, Au@Cu 2 O-SDS shell is unstable and easily falls off. The most stable Au@Cu 2 O nanostructures with rough surfaces were synthesized using anionic polymer PAA. Thus, this study provides an effective way to control the nanostructures and stability of the metal-semiconductor heterostructures. [ABSTRACT FROM AUTHOR]

Surface ligands play a critical role in controlling and defining the properties of colloidal nanocrystals. These aspects have been exploited to design nanoparticle aggregation-based colorimetric sensors. Here, we coated 13-nm gold nanoparticles (AuNPs) with a large library of ligands ( e.g. , from labile monodentate monomers to multicoordinating macromolecules) and evaluated their aggregation propensity in the presence of three peptides containing charged, thiolate, or aromatic amino acids. Our results show that AuNPs coated with the polyphenols and sulfonated phosphine ligands were good choices for electrostatic-based aggregation. AuNPs capped with citrate and labile-binding polymers worked well for dithiol-bridging and π-π stacking-induced aggregation. In the example of electrostatic-based assays, we stress that good sensing performance requires aggregating peptides of low charge valence paired with charged NPs with weak stability and vice versa . We then present a modular peptide containing versatile aggregating residues to agglomerate a variety of ligated AuNPs for colorimetric detection of the coronavirus main protease. Enzymatic cleavage liberates the peptide segment, which in turn triggers NP agglomeration and thus rapid color changes in <10 min. The protease detection limit is 2.5 nM.

A series of CuInZn x S 2+ x QDs has been successfully synthesized via a non-injection method by varying the amine (oleylamine, dioctylamine, dodecylamine, octadecylamine) during the ZnS shell introduction on the CuInS 2 core. The effects of these amines on the photoluminescence (PL) and on the morphology of CuInZn x S 2+ x QDs were explored. The optical features and structure of the obtained CuInZn x S 2+ x QDs have been characterized by UV–visible and fluorescence spectroscopies, time resolved PL, HR-TEM, XRD and EDX. After the ZnS shell introduction at 220 °C, CuInZn x S 2+ x QDs showed greatly improved properties, the PL quantum yield can reach up to 70% using dioctylamine. The formation of CuInZn x S 2+ x QDs results in a blue shift of both the absorption and PL due to the formation of the alloyed interfacial layer at CuInS 2 /ZnS during the shell growth. By increasing the reaction temperature to 250 °C (thermolysis of CuInZn x S 2+ x QDs), marked red-shifts in PL emissions accompanied by morphological changes of the nanocrystals were observed. The use of oleylamine generates 6.6 nm-sized pyramidally-shaped nanocrystals with a PL quantum yield of 22%. [ABSTRACT FROM AUTHOR]

The engineering of quantum dot solids with low defect concentrations and efficient carrier transport through a ligand strategy is crucial to achieve efficient quantum dot (QD) optoelectronic devices. Here, we study the consequences of various surface ligand treatments on the light emission properties of PbS quantum dot films using 1,3-benzenedithiol (1,3-BDT), 1,2-ethanedithiol (EDT), mercaptocarboxylic acids (MPA) and ammonium sulfide ((NH4)2S). We first investigate the influence of different ligand treatments on the inter-dot separation, which mainly determines the conductivity of the QD films. Then, through a combination of photoluminescence and transient photoluminescence characterization, we demonstrate that the radiative and non-radiative recombination mechanisms in the quantum dot films depend critically on the length and chemical structure of the surface ligands [ABSTRACT FROM AUTHOR]

A micro-beam scanning X-ray photoelectron spectroscopy (XPS) has been utilized to obtain information about the attachment of ligand to nanoparticles in solution by measuring the ligand components relative to nanoparticle components. CdSe/ZnS core/shell nanoparticles capped with three different kinds of ligand molecules are drop-casted on a substrate and led to dry into self-agglomerated micropatterns. Those specimens are mapped out by element-sensitive XPS imaging. The spatial correlation between surface ligand molecules and core nanoparticle atoms is statistically analysed using Pearson correlation function, which provides with a useful assessment of the ligand binding to nanoparticle surfaces. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Surface-enhanced infrared absorption (SEIRA) spectroscopy has been developed for the nondestructive analysis of trace molecules. Herein, we found that ethylene glycol (EG) decorated TiO 2 nanosheet exhibits a selective SEIRA effect for molecules with nucleophilic groups, such as -NH 2 and -OH. The SEIRA effect was attributed to the chemical mechanism originating from the interactions between the surface EG and the analytes. The enhancement factor was negatively correlated with the electrophilicity index of the analytes ( p = 0.004), and the noncovalent bond dominates the interactions between the analytes and EG. The charge distribution analysis revealed that the -CH 2 groups of EG exposed on the TiO 2 surface are positively charged, attracting the electron-rich groups of the analyte. This attraction concentrates the analyte, redistributes its charge, defines its molecular dipole moment, and thereby enhances the SEIRA effect. The insights gained from this study shed light on developing new SEIRA substrates and emphasized the critical role of surface ligands in SEIRA applications.

Abstract: The interaction of thiols (glutathione, cysteine, and cysteamine) with yellow-emitting siloxane-capped ZnO QDs was studied. A gradual enlargement of the PL emission band resulting in white-light emission was observed upon reaction with thiols, while the diameter (ca. 4nm) and the crystallinity of the dots were not affected. The appearance of broad white-emission was accompanied by a decrease of the photoluminescence quantum yield from 16% to 5–6%. Generation of surface defect states through interaction of the thiols with Zn surface atoms of the dots provoking shrunk of the siloxane capping may be responsible of that broadband emission throughout most of the light spectrum. [Copyright &y& Elsevier]

Two kinds of hybrid ultraviolet (UV) photodetectors based on TiO nanocrystals capped with and without oleic acid (OA) and poly(9,9-dihexylfluorene) (PFH) were prepared from solution and characterized to study the effects of the surface ligand on the device function. Both devices showed obvious photovoltaic effect, high UV-sensitive photoconductivity, and fast response time. The hybrid device containing TiO nanocrystals with bare surface exhibited a photocurrent density of 91 μA/cm at zero bias under 3.2 mW/cm UV irradiation, corresponding to a photosensitivity of 28.4 mA/W. The other device containing OA-capped TiO nanocrystals showed a photocurrent density of 19 μA/cm and a photosensitivity of 5.9 mA/W under the same condition. It was found that capping TiO with OA had a beneficial effect on its solubility in organic solvent. On the contrary, a barrier might be formed, significantly influencing the charge-transfer behavior. This negative effect overcompensated the positive influence due to improved morphology and lowered the photosensitivity of the device. [ABSTRACT FROM AUTHOR]

Superparamagnetic iron oxide nanoparticles have been used for many years as magnetic resonance imaging contrast agents or in drug delivery applications. Tissue and cell-specific drug targeting by these nanoparticles can be achieved by employing nanoparticle coatings or carrier-drug conjugates that contain a ligand recognized by a receptor on the target cell. In this study, superparamagnetic iron oxide nanoparticles with specific shape and size have been prepared and coupled to insulin for their targeting to cell expressed surface receptors and thereby preventing the endocytosis. The influence of these nanoparticles on human fibroblasts is studied using various techniques to observe cell-nanoparticle interaction that includes light, scanning, and transmission electron microscopy studies. The derivatization of the nanoparticle surface with insulin-induced alterations in cell behavior that were distinct from the underivatized nanoparticles suggests that cell response can be directed via specifically engineered particle surfaces. The results from cell culture studies showed that the uncoated particles were internalized by the fibroblasts due to endocytosis, which resulted in disruption of the cell membrane. In contradiction, insulin-coated nanoparticles attached to the cell membrane, most likely to the cell-expressed surface receptors, and were not endocytosed. The presence of insulin on the surface of the nanoparticles caused an apparent increase in cell proliferation and viability. One major problem with uncoated nanoparticles has been the endocytosis of particles leading to irreversible entry. These results provide a route to prevent this problem. The derivatized nanoparticles show high affinity for cell membrane and opens up new opportunities for magnetic cell separation and recovery that may be of crucial interest for the development of cellular therapies. [ABSTRACT FROM PUBLISHER]

Copper sulfide nanoparticles (Cu x S-NP) surface-stabilized by dithiocarbamate (DTC) molecules were obtained with controlled size and shape by a novel one-step wet chemical methodology for the chemical transformation of a single-source precursor. The reaction of N-alkyldithiocarbamatecopper(II) complexes with NaBH 4 in ethanol solution produces Cu x S-NP of hexyl- (NP6), dodecyl- (NP12), and octadecyl- (NP18) carbon chains. The characterization of the particles was carried out by IR spectroscopy, Diffuse Reflectance Spectroscopy, Powder X-ray Diffraction, Thermal Analyses, and Transmission Electron Microscopy. The Cu x S-NP are capped with DTC ligands which can tune the particle size. The Cu x S phases obtained are closely related to the DTC chains length since NP6 produces Cu 9 S 5 and CuS, NP12 yields Cu 9 S 5 and Cu 2 S, finally, Cu 9 S 5 and CuS are produced with NP18. In all the cases, the particles have a quasi-spherical shape, and the length of the DTC chain controls the particle size. The band gap of the Cu x S-NP is around 3.0 eV, calculated by the Tauc baseline method, confirming their semiconductor nature and strong quantum confinement. [Display omitted] • A chemical strategy to obtain Cu x S nanoparticles. • Dithiocarbamate ligand remains in the nanoparticle. • Cu 9 S 5 and CuS (or Cu 2 S) phases present in the particles. • Discrete size distribution of Cu x S-NP. • Cu x S-NP band gaps reflect quantum size effect. [ABSTRACT FROM AUTHOR]

The potential toxicity of nanoplastics on plants has previously been illustrated, but whether nanoplastics could cause neurotoxicity, especially to higher animals, remains unclear. We now demonstrate that nanoplastics can be deposited in the brain via nasal inhalation, triggering neuron toxicity and altering the animal behavior. Polystyrene nanoparticles (PS-NPs) of PS-COOH and PS-NH 2 are used as models for nanoplastics. We designed a microfluidic chip to evaluate the PS-NPs with different concentrations, surface ligands, and sizes to interact with neurons. Smaller PS-NPs can induce more cellular uptake than larger PS-NPs. PS-NPs with a size of 80 nm can reach and deposit in the brain of mice via aerosol inhalation. Mice inhaling PS-NPs exhibit fewer activities in comparison to those inhaling water droplets. An obvious neurotoxicity of the nanoplastics could be observed from the results of the inhibition of AChE activities. Our results show the potential significance of the physiochemical properties of organic nanoplastics on depositing in mammalian brains by nasal inhalation.

Analytical ultracentrifugation (AUC) is a powerful technique to observe colloidal nanocrystals (NCs) directly in solution and obtain critical information about their physical-chemical properties. Nevertheless, a more comprehensive implementation of AUC for the characterisation of such a class of crystalline colloids has been traditionally impaired by the requirement of having a priori knowledge of the complex, multilayered structure formed by NC in solution. This includes the nature (density and mass) of the surface ligands (SLs) that provide NC colloidal stability and the shell of solvent molecules formed on it. Herein, we propose a methodology to determine the NCs size by using SLs with a density equal to that of the solvent. Thereby, the buoyancy force of the SL shell is neutral, and the density of the NCs is sufficient a priori knowledge to calculate their related mass and size distributions. The simplicity and reliability of the method are evaluated with cetyltrimethylammonium bromide (CTAB) stabilized spherical gold NCs (AuNCs) of dimensions ranging from 1 to 17 nm. The proposed method has great potential to be transferred to any non-crystalline and crystalline colloids of different nature and composition, which have a density that is equal to the bulk and can be stabilized by SLs having a density that matches that of the solvent. [ABSTRACT FROM AUTHOR]

N , N , N ', N '-Tetramethylethylenediamine (TMEDA) and ethylenediamine (EDA) were investigated in-depth in the ligand exchanges for water-soluble CdSe quantum dots (QDs). TMEDA could assist the phase transfer of QDs from apolar solvents to the aqueous solutions as stabilized by mercaptopropionic acid (MPA). We successfully maintained the stability of a series of MPA-capped QDs of different ligand densities for NMR characterizations in aqueous solutions. The proton NMR spectroscopies of MPA of the binding state were used to analyze the ligand densities on the surface of QDs, which were not explored in the past. The binding thermodynamics of the surface ligands of QDs, as analyzed using the Hill equation, demonstrated a positive promoting effect and possible interactions between ligands. EDA in the purification process underwent a spontaneous adsorption with two-stage thermodynamic behaviors as characterized by isothermal titration calorimetry. Due to the positive role of the already adsorbed ligands, excess EDA would further attach to the surface of QDs in the form of non-bonded physisorption, greatly improving the quantum yield (QY) of QDs, and the ligand of this part would almost not change the stability of QDs. We proposed a strategy for the preparation of aqueous QDs with a high QY, followed by fluorescence quenching-enhancement cycles caused by purification-adsorption operations. The strategy made it possible for the preparation of functional QDs with small molecules after purification operations. Kinetics of the sorption of ligands on the surface of QDs were determined by fluorescence spectroscopy. Modified pseudo-second-order kinetics after consideration of the ligand-ligand interaction effect could well analyze the kinetic data. This kinetic model had advantages over the previous ligand exchange model in terms of accuracy, reproducibility, and physical significance. Finally, we used the above strategy for the design of fluorescent QDs for bioimaging of lysosomes, mitochondria, and cancer cells. This work can simplify the preparation of multifunctional fluorescent QDs and avoid complicated ligand design.

A facile approach for activating the surface of CdSe NCs by stripping the carboxylate ligands with an alkylammonium–selenide complex, thereby providing building blocks for functional nano-superstructures. • The surface of CdSe nanocrystals is activated using the (Se n 2−)(OAm–H+) 2 complex. • Coalescence between surface activated CdSe nanocrystals readily occurred. • Hetero-nano-superstructures can be formed using activated CdSe and CdS nanocrystals. • Activated CdSe nanocrystals would be applied to soldering on solid substrate. Exploiting colloidal semiconductor nanocrystals (NCs) as building blocks for higher-order nanostructures can expand the field of nanoscience. For this reason, understanding the controlled coalescence of colloidal semiconductor NCs passivated with surface ligands is a big challenge for nanoscience research. Herein, we report a facile approach for activating the surface of CdSe NCs by stripping the carboxylate ligands with an alkylammonium–selenide complex for coalescence. The surface of as-prepared CdSe NC turned sparsely passivated and stoichiometric by the addition of alkylammonium–selenide complex; subsequently, coalescence readily occurred. Controlled coalescence or heterostructures can be realized through sophisticated control of the surface state of NCs. We anticipate that the surface-activated colloidal semiconductor NCs will act as promising nanoscale building blocks for fabricating functional nanostructures. Using a method described in this work, it is possible to not only understand the formation mechanism of coalescence, but to also construct higher-order supernanostructures. [ABSTRACT FROM AUTHOR]

Lead-halide perovskite nanocrystals (NCs) are limited in commercial applications due to their high lead content. Developing lead-free perovskite NCs becomes a new choice. Among them, the tin-halide perovskite NCs exhibit the excellent photoelectric conversion efficiency, but has worse stability. Herein we describe an effective approach to the preparation of highly-stable all-inorganic tin-based perovskite NCs by using gelatin via interfacial passivation and coating, which leads to the retention of 77.46% of photoluminescence intensity even after the dispersion of the NCs in water for 3 d. The results show that gelatin form a "rich ligand" state on NC surface, such as amino-Sn, carboxylate-Sn and halogen-ammonium hydrogen-bonding interactions. The amino-Sn coordination would be replaced by carboxylate-Sn coordination when NCs are dispersed in polar-media. Meanwhile, gelatin is imparted excellent anti-mildew properties by NCs, which ensures long-lasting effect to NCs. This will promote the stability and sustainable development of the perovskite device. ga1 • The optical properties of tin-based perovskite nanocrystals are improved by the passivation of gelatin. • The stability of tin-based perovskite nanocrystals passivated and C by gelatin is greatly enhanced. • When encountering polar solvent attack, Sn-carboxylate bond will replace amino-Sn bond on the surface of gelatin-NCs. • Gelatin is imparted excellent anti-mildew properties by NCs, which ensured long-lasting effect to NCs. [ABSTRACT FROM AUTHOR]

With the widespread use of antibiotics, the number of complex infection cases caused by unknown pathogens is increasing and novel antibiotics with tunable antibacterial spectra and low toxicity are highly desirable. Herein, we report that, by selecting thiol or amine, two groups with different binding affinities with gold, as anchoring groups, phenylboronic acid can be decorated on gold nanoparticles (AuNPs) with different densities, which contributes to Gram-selective antibacterial activities of the AuNPs. The AuNPs modified with amine- or thiol-tethered phenylboronic acids specifically bind to lipopolysaccharide (LPS, Gram-negative) or lipoteichoic acid (LTA, Gram-positive), respectively. By modifying AuNPs with different ratios of thiol- and amine-tethered phenylboronic acids, the resulting AuNPs show potent and tunable antibacterial activity. The AuNP-based antibacterial agents with optional Gram selectivity are promising for applications in personalized therapy.