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Background: Research into perovskite nanocrystals (PNCs) has uncovered interesting properties compared to their bulk counterparts, including tunable optical properties due to size‐dependent quantum confinement effect (QCE). More recently, smaller PNCs with even stronger QCE have been discovered, such as perovskite magic sized clusters (PMSCs) and ligand passivated PbX2 metal halide molecular clusters (MHMCs) analogous to perovskites. Objective: This review aims to present recent data comparing and contrasting the optical and structural properties of PQDs, PMSCs, and MHMCs, where CsPbBr3 PQDs have first excitonic absorption around 520 nm, the corresponding PMSCS have absorption around 420 nm, and ligand passivated MHMCs absorb around 400 nm. Results: Compared to normal perovskite quantum dots (PQDs), these clusters exhibit both a much bluer optical absorption and emission and larger surface‐to‐volume (S/V) ratio. Due to their larger S/V ratio, the clusters tend to have more surface defects that require more effective passivation for stability. Conclusion: Recent study of novel clusters has led to better understanding of their properties. The sharper optical bands of clusters indicate relatively narrow or single size distribution, which, in conjunction with their blue absorption and emission, makes them potentially attractive for applications in fields such as blue single photon emission. [ABSTRACT FROM AUTHOR]

Organo‐metal halide perovskites (OMHPs) are currently one of the most exciting candidates for photovoltaics. However, their impact in other areas related to carrier photogeneration, such as in luminescent solar concentrators (LSCs), has been limited. OMHP thin films have demonstrated encouraging results as LSCs, but for a scalable platform with minimal losses, discrete emitters are preferable. Perovskite quantum dots (PQDs) possess higher photoluminescence quantum yield (PLQY) than their thin film counterparts, and have the added advantage of size tunability, which make them well‐suited as LSC active media. However, since PQDs are not amenable to Stokes shift modulation, large‐scale samples will suffer from increased self‐absorption (SA) losses. In this work, a facile dip‐coating approach is established to fabricating large‐scale LSCs with CH3NH3PbBr3 (methylammonium lead bromide) PQDs by leveraging their plasmonic interactions with gold nanoparticles (AuNPs) to offset SA losses. Optical characterization through emission, lifetime, and spatially resolved photoluminescence measurements provide insight into the effect of plasmon resonance on deposited PQDs, and leveraging this AuNP‐PQD coupling, 2.87% efficiency is achieved in a 100 cm2 LSC with a geometric gain of 50. [ABSTRACT FROM AUTHOR]

Hollow gold nanospheres (HGNs) are core/shell structures with a dielectric material core, usually composed of solvent, and a gold metal shell. Such structures have two metal/dielectric interfaces to allow interaction between the gold metal with the interior and external dielectric environment. Upon illumination by light, HGNs exhibit unique surface plasmon resonance (SPR) properties compared to solid gold nanoparticles. Their SPR absorption/scattering can be tuned by changing their diameter, shell thicknesses, and surface morphologies. In addition to the low toxicity, easy functionalization, resistance to photobleaching, and sensitivity to changes in surrounding medium of gold, the enhanced surface‐to‐volume ratio and tunable SPR of HGNs make them highly attractive for different applications in the fields of sensing, therapy, and theranostics. In this article, we review recent progress on the synthesis and structural control of HGNs and applications of their SPR properties in biomedical sensing and theranostics. This article is categorized under:Diagnostic Tools > BiosensingDiagnostic Tools > in vitro Nanoparticle‐Based SensingDiagnostic Tools > in vivo Nanodiagnostics and Imaging [ABSTRACT FROM AUTHOR]

Heteroatom‐doped carbon materials are promising electrocatalysts towards the oxygen reduction reaction (ORR). In this study, dual metals (Fe an Co) and nitrogen‐codoped porous carbon cages (CHS−FeCo) were synthesized by controlled pyrolysis of silica nanoparticle‐supported melamine‐formaldehyde resin embedded with iron and cobalt precursors, followed by acid etching. Transmission electron microscopy measurements confirmed the formation of hollow carbon cages, and the absence of metal (oxide) nanoparticles suggested atomic dispersion of the metal species within the mesoporous carbon skeletons. X‐ray photoelectron spectroscopic analysis revealed a composition of mostly carbon, oxygen, and nitrogen, with ca. 1 % metals. Electrochemically, the dual‐metal ones showed a significant enhancement of the catalytic performance towards ORR in alkaline media, as compared to samples with single or no metal dopants. This was accounted for by the synergistic interaction between the Fe and Co centers in the carbon samples, as evidenced in X‐ray absorption spectroscopic studies. Remarkably, the CHS−FeCo sample exhibited apparent resistance against KSCN poisoning, where XPS analysis revealed oxidation of KSCN and no metal‐sulfur interaction, in sharp contrast to the Fe counterpart which was easily poisoned. Results from this study suggest that the synergistic interactions between dual metal centers may be exploited for enhanced ORR performance of carbon‐based nanocomposite catalysts. [ABSTRACT FROM AUTHOR]

Here, it is demonstrated that the size tunable hollow gold nanospheres (HGNs) of ≈24-122 nm in diameter can be facilely achieved by controlling a signal parameter, reaction temperature, in the synthesis. The varied particle sizes of HGNs result in highly tunable surface plasmon resonance (SPR) absorption in the entire visible to near infrared region of the spectrum, with maximum peak position from 565 to 850 nm when the reaction temperature is varied from 80 to 10 °C. The particle size and structural properties are determined using dynamic light scattering, transmission-mode scanning electron microscopy, and high-resolution transmission electron microscopy. The optical properties are characterized using UV-vis spectroscopy. A mechanism behind the temperature-dependent HGN synthesis is explained by the thermodynamics of homogeneous nuclei formation of the cobalt scaffold. Discrete dipole approximation calculations are performed to simulate the SPR spectrum and provide insight into the relation between the SPR absorption and structural details of the HGNs. This study demonstrates a simple yet effective method based on temperature control for synthesizing produce size tunable HGNs with varying properties of interest for different applications. [ABSTRACT FROM AUTHOR]

Lead halide (LH) perovskites have received enormous attention recently because of their interesting optoelectronic properties and high power conversion efficiency (PCE) in photovoltaic solar cells. However, material instability toward factors such as water, UV light, temperature, and oxygen have presented a major challenge for practical applications. Recently, LH perovskite nanocrystals (PNCs) have also drawn increasing attention owing to their tunable optical properties and ability to serve as model systems for studying the mechanism of material instability or degradation. Surface passivation of PNCs is critical to achieving high stability and desired optical properties. In this review, we highlight several surface passivation strategies developed for improving the stability of LH perovskites and synthesizing PNCs with different morphologies as a promising class of materials for photovoltaics, light-emitting diodes (LEDs), and sensing applications. [ABSTRACT FROM AUTHOR]

A new strategy has been developed using peptides with amino and carboxylic functional groups as passivating ligands to produce methyl ammonium lead bromide (CH3NH3PbBr3) perovskite nanocrystals (PNCs) with excellent optical properties. The well-passivated PNCs can only be obtained when both amino and carboxylic groups are involved, and this is attributed to the protonation reaction between NH2 and COOH that is essential for successful passivation of the PNCs. To better understand this synergistic effect, peptides with different lengths have been studied and compared. Due to the polar nature of peptides, peptide-passivated PNCs (denoted as PNCspeptide) aggregate and precipitate from nonpolar toluene solvent, resulting in a high product yield (≈44%). Furthermore, the size of PNCspeptide can be varied from ≈3.9 to 8.6 nm by adjusting the concentration of the peptide, resulting in tunable optical properties due to the quantum confinement effect. In addition, CsPbBr3 PNCs are also synthesized with peptides as capping ligands, further demonstrating the generality and versatility of this strategy, which is important for generating high quality PNCs for photonics applications including light-emitting diodes, optical sensing, and imaging. [ABSTRACT FROM AUTHOR]

CH3NH3PbBr3 perovskite nanocrystals (PNCs) of different sizes (ca. 2.5-100 nm) with high photoluminescence (PL) quantum yield (QY; ca. 15-55 %) and product yield have been synthesized using the branched molecules, APTES and NH2-POSS, as capping ligands. These ligands are sterically hindered, resulting in a uniform size of PNCs. The different capping effects resulting from branched versus straight-chain capping ligands were compared and a possible mechanism proposed to explain the dissolution-precipitation process, which affects the growth and aggregation of PNCs, and thereby their overall stability. Unlike conventional PNCs capped with straight-chain ligands, APTES-capped PNCs show high stability in protic solvents as a result of the strong steric hindrance and propensity for hydrolysis of APTES, which prevent such molecules from reaching and reacting with the core of PNCs. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel drug-polymer conjugate was prepared by the copper-catalyzed azide-alkyne cycloaddition reaction between an azide-functional diblock copolymer and an alkyne-functional paclitaxel (PTX). The well-defined azide-functional diblock copolymer, poly(ethylene glycol) (PEG)- b-P(OEGEEMA- co-AzPMA), was synthesized via the atom transfer radical polymerization of oligo(ethylene glycol) ethyl ether methacrylate (OEGEEMA) and 3-azidopropyl methacrylate (AzPMA), using PEG-Br as macroinitiator and CuBr/PMDETA as a catalytic system. The alkyne-functional PTX was covalently linked to the copolymer via a click reaction, and the loading content of PTX could be easily tuned by varying the feeding ratio. Transmission electron microscopy and dynamic light scattering results indicated that the drug loaded copolymers could self-assemble into micelles in aqueous solution. Moreover, the drug release behavior of PEG- b-P(OEGEEMA- co-AzPMA-PTX) was pH dependent, and the cumulative release amount of PTX were 50.0% at pH 5.5, which is about two times higher than that at pH 7.4. The in vitro cytotoxicity experimental results showed that the diblock copolymer was biocompatible, with no obvious cytotoxicity, whereas the PTX-polymer conjugate could efficiently deliver PTX into HeLa and SKOV-3 cells, leading to excellent antitumor activity. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 366-374 [ABSTRACT FROM AUTHOR]

Much progress has been made in using hematite (α-Fe2O3) as a potentially practical and sustainable material for applications such as solar-energy conversion and photoelectrochemical (PEC) water splitting; however, recent studies have shown that the performance can be limited by a very short charge-carrier diffusion length or exciton lifetime. In this study, we performed ultrafast studies on hematite nanoparticles of different shapes to determine the possible influence of particle shape on the exciton dynamics. Nanorice, multifaceted spheroidal nanoparticles, faceted nanocubes, and faceted nanorhombohedra were synthesized and characterized by using SEM and XRD techniques. Their exciton dynamics were investigated by using femtosecond transient absorption (TA) spectroscopy. Although the TA spectral features differ for the four samples studied, their decay profiles are similar, which can be fitted with time constants of 1-3 ps, approximately 25 ps, and a slow nanosecond component extending beyond the experimental time window that was measured (2 ns). The results indicate that the overall exciton lifetime is weakly dependent on the shape of the hematite nanoparticles, even though the overall optical absorption and scattering are influenced by the particle shape. This study suggests that other strategies need to be developed to increase the exciton lifetime or to lengthen the exciton diffusion length in hematite nanostructures. [ABSTRACT FROM AUTHOR]

In article no. 1800285, Shaohua Shen and co‐workers rationally design and fundamentally characterize an interfacial α‐Fe2O3/TiO2 structure to explore its electronic structure evolution for the synergy of the promoted interface charge transfer processes and the accelerated water oxidation electrocatalysis, contributing to the greatly enhanced photoelectrochemical water splitting activities. [ABSTRACT FROM AUTHOR]