Nanocuboids Research Articles

Aluminium-Based Metal-Organic Framework Nano Cuboids and Nanoflakes with Embedded Gold Nanoparticles for Carbon Dioxide Fixation with Epoxides into Cyclic Esters.

The fixation of carbon dioxide with epoxides is one of the most attractive methods for the green utilisation of this greenhouse gas and leads to many valuable chemicals. This process is characterised by 100% atom efficiency; however, an efficient catalyst is required to achieve satisfactory yields. Metal-organic frameworks (MOFs) are recognised as being extremely promising for this purpose. Nevertheless, many of the proposed catalysts are based on ions of rare elements or elements not entirely safe for the environment; this is notable with commercially unavailable ligands. In an effort to develop novel catalysts for CO2 fixation on an industrial scale, we propose novel MOFs, which consist of aluminium ions coordinated with commercially available 1,4-naphthalene dicarboxylic acid (Al@NDC) and their nanocomposites with gold nanoparticles entrapped inside their structure (AlAu@NDC). Due to the application of 4-amino triazole and 5-amino tetrazole as crystallization mediators, the morphology of the synthesised materials can be modified. The introduction of gold nanoparticles (AuNPs) into the structure of the synthesised Al-based MOFs causes the change in morphology from nano cuboids to nanoflakes, simultaneously decreasing their porosity. However, the homogeneity of the nanostructures in the system is preserved. All synthesised MOF materials are highly crystalline, and the simulation of PXRD patterns suggests the same tetragonal crystallographic system for all fabricated nanomaterials. The fabricated materials are proven to be highly efficient catalysts for carbon dioxide cycloaddition with a series of model epoxides: epichlorohydrin; glycidol; styrene oxide; and propylene oxide. Applying the synthesised catalysts enables the reactions to be performed under mild conditions (90 °C; 1 MPa CO2) within a short time and with high conversion and yield (90% conversion of glycidol towards glycerol carbonate with 89% product yield within 2 h). The developed nanocatalysts can be easily separated from the reaction mixture and reused several times (both conversion and yield do not change after five cycles). The excellent performance of the fabricated catalytic materials might be explained by their high microporosity (from 421 m2 g-1 to 735 m2 g-1); many catalytic centres in the structure exhibit Lewis acids' behaviour, increased capacity for CO2 adsorption, and high stability. The presence of AuNPs in the synthesised nanocatalysts (0.8% w/w) enables the reaction to be performed with a higher yield within a shorter time; this is especially important for less-active epoxides such as propylene oxide (two times higher yield was obtained using a nanocomposite, in comparison with Al-MOF without nanoparticles).

Outdoor Characterization of a Plasmonic Luminescent Solar Concentrator

Plasmonic luminescent solar concentrators (PLSCs) have been shown to enhance the optical performance and power conversion efficiency of LSCs, due to added plasmonic gain in the medium. Despite the promising outlook of a PLSC through plasmonic coupling, device characterization and performance have not been verified in the real outdoor conditions, with varying direct and diffuse solar irradiation. In this work, characterization of a PLSC device of dimensions 4.5 \(\times\) 4.5 \(\times\) 0.3 cm3 embedded with Lumogen Red 305 dye and plasmonic gain medium of gold core silver shell nano cuboids was carried out in outdoor conditions of Dublin, Ireland. Optimized PLSC device power output at different solar insolation was compared to a reference photovoltaic (PV) cell and an optimized luminescent solar concentrator (LSC) device. The effect of the solar disc position, solar insolation, PV cell surface temperature, diurnal, and seasonal variation on the performance of the PLSC device is studied. The key observation was that PLSC average power conversion efficiency was 1.4 times more than the PV cell in cloudy and diffuse solar conditions. The PLSC device performed 45% better than a PV cell in December than July, as December has higher diffuse solar irradiation. Even though the PLSC device absorbs only 31% and transmits 69% incident solar irradiation in the concerned visible range of 380–750 nm. The preliminary outdoor characterization on a small-scale PLSC establishes its viability in a diffuse to direct solar radiation ratio throughout the year as well as establishing its benefits for integration in buildings.

A generalized model for the prediction of the permeability of mixed-matrix membranes using impermeable fillers of diverse geometry

In this paper, we propose a model to predict the relative permeability of ideal MMMs, which requires the specification of only two geometrical parameters: the relative projected area available for permeation and the relative thickness of the nanofiller. The model, which was initially developed for MMMs with impermeable nano cuboids, provides excellent predictions for nanofillers with a constant relative thickness (i.e., vertical cylindrical and elliptical rods and vertical tubes) with the average prediction error not exceeding 2.1%. For nanofillers with a variable relative thickness (i.e., spheres, horizontal cylindrical and elliptical rods, horizontal tubes), the model is still excellent using the average relative thickness, which is the ratio of the volume fraction and the projected area of the nanofiller. The corresponding average prediction error does not exceed 8%. Except for spherical nanofillers, the model is superior to seven theoretical models commonly used in the literature. After introducing a simple correction factor, the prediction error decreases to 2.3% or less for spheres and horizontal cylindrical and elliptical rods.

Parameter optimization of tetracycline removal by vanadium oxide nano cuboids

Massive production and widespread use of antibiotics have led to concerns about negative outcomes for the environment and human health. In particular, tetracycline (TC) is a persistent and highly soluble chemical that threatens global water security. In this work, the utility of vanadium oxide nano cuboids (VONCs) as a mesoporous, non-toxic, stable, and low-cost material was studied for TC adsorption properties. Optimization of the experimental conditions for TC uptake was carried out using the response surface methodology (RSM) where the model showed that the adsorbent dose was the key variable affecting TC sorption. Moreover, the model indicated a 20% suppression in TC removal as the pH decreased from 9 to 3. The TC removal increased by 30% upon increasing the adsorbent dose (0.1–0.5 g/L) and initial TC concentration (25–100 mg/L) values. RSM optimization afforded 100% adsorptive removal at the following conditions: pH = 4.1, mixing time of 44.5 min, VONCs dosage of 0.49 g/L for a fixed TC concentration (30.7 mg/L TC). Equilibrium sorption data for VONCs agreed well with the Langmuir model, where an estimated monolayer sorption capacity for TC (126.8 mg/g) was obtained. The separation factor (RL) for variable TC concentration covered a range of values (0.02–0.19), which is indicative of a favorable process. A study of the sorption mechanism revealed that the rate-controlling step of the sorption process depended on the mutual diffusion of VONCs and TC. The sorption of TC by VONCs is characterized by an exothermic process that was favorable at room temperature, where TC removal showed a mild suppression (16%) in the presence of co-adsorbates in real wastewater.

Nano cuboids: Impact of 8-hydroxyquinoline on tryptophan properties and its applications

N-terminal tryptophan residues can be labeled with fluorophore by chemical reaction. Here in we report conjugation of 8-hydroxyquinoline (as fluorophore) with tryptophan using Schiff-base condensation reaction to decipher the impact of 8-hydroxyquinoline on the fluorescence and self-assembly properties of tryptophan in water. This water-soluble hydroxyquinoline–tryptophan (HQ-W1) conjugate has been demonstrated to have Aggregation Induced Emission (AIE) phenomena in water. HQ-W1 undergo spontaneous self-assembly to form nano cuboidal superstructures having 200–500 nm diameter and 300–650 nm length. In metal-ion binding studies this HQ-W1 shows selective fluorescence enhancement (14.5-fold) in the presence of Al3+ ions. The detection limit is 3.0 nM (UV method) and 3.53 nM (FI method). The AIE utility of HQ-W1 has been demonstrated by developing latent fingerprints.

Broadband plasmonic coupling and enhanced power conversion efficiency in luminescent solar concentrator

Advancements in solar energy harvesting technologies call for innovative approaches to meet the ever-growing energy demand. This study exploits the plasmonic interaction of metal nanoparticles (MNPs) with fluorophores to improve the optical performance of Luminescent Solar Concentrators (LSCs). Plasmonic Luminescent Solar Concentrator (PLSC) with dimensions of 45 × 45 × 3 mm3 containing Lumogen Red305 dye and gold core silver shell nanocuboids (Au@Ag NCs) were fabricated and characterized. Plasmonic coupling in the PLSC device was influenced through spacing and spectral overlap between the nanocuboids (NCs) and Red305 dye. The spacing between Au@Ag NCs and Red305 dye was controlled by the doping concentration of Au@Ag NCs for acquiring a homogeneous sample. The optical performance of PLSC waveguides was investigated through edge emission measurements of the waveguides while varying the doping concentration of Au@Ag NCs. A maximum enhancement of 30% in the fluorescence was achieved for PLSC device containing an optimal doping concentration (1.1 ppm) of Au@Ag NCs. A transition from maximum fluorescence enhancement to quenching was demonstrated, emphasizing the importance of MNP doping concentration and spectral overlap when coupling Au@Ag NC and Red305 dye molecules. At high doping concentrations of Au@Ag NCs, non-radiative energy transfer from Red305 dye molecules to the Au@Ag NCs made quenching a dominant effect. Monocrystalline silicon solar cells were attached to one edge of the PLSC waveguides. For the sample with 1.1 ppm Au@Ag NCs doping concentration, the power conversion efficiency was found to be 1.2 times higher than the power conversion efficiency of 0 ppm sample.

Enhanced photovoltaic property and stability of perovskite solar cells using the interfacial modified layer of anatase TiO2 nanocuboids

The substrates were significant for fabricating the high performance and outstandingly stable perovskite solar cells (PSCs) due to the influences of films growth and pores filling. In this paper, we study the effects of interface modification with TiO2 nanoparticles (NPs) and nanocuboids (NCs) synthesized by the TiCl4 and NaF/TiCl4 solution, prepared on nanorods (NRs) substrates, on the PSCs performance. The devices modified with NPs and NCs exhibit power conversion efficiency (PCE) of 12.97% and 15.56%, respectively, which are 1.3 and 1.5 times greater than that of the untreated cell (10.29%). By carefully analyze the photovoltaic parameters, the improvements in the open-circuit voltage (Voc) and fill factor (FF) can be attributed to the optimization of the interfacial properties of perovskite-titania and the quality of perovskite films after the surface treatment. The novel TiO2 NCs obtained by NaF/TiCl4 treatment were found to expose highly reactive (001) facets, which may promote the absorption of perovskite materials due to the more effective area, resulting in the increment of short-circuit current density (Jsc) compared to simplex TiCl4 treatment. In addition, the device modified by the NCs shows the higher stability in the air atmosphere than other devices.

Enhanced Photocatalytic Performance and Mechanism of Au@CaTiO3 Composites with Au Nanoparticles Assembled on CaTiO3 Nanocuboids.

Using P25 as the titanium source and based on a hydrothermal route, we have synthesized CaTiO3 nanocuboids (NCs) with the width of 0.3–0.5 μm and length of 0.8–1.1 μm, and systematically investigated their growth process. Au nanoparticles (NPs) of 3–7 nm in size were assembled on the surface of CaTiO3 NCs via a photocatalytic reduction method to achieve excellent Au@CaTiO3 composite photocatalysts. Various techniques were used to characterize the as-prepared samples, including X-ray powder diffraction (XRD), scanning/transmission electron microscopy (SEM/TEM), diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Rhodamine B (RhB) in aqueous solution was chosen as the model pollutant to assess the photocatalytic performance of the samples separately under simulated-sunlight, ultraviolet (UV) and visible-light irradiation. Under irradiation of all kinds of light sources, the Au@CaTiO3 composites, particularly the 4.3%Au@CaTiO3 composite, exhibit greatly enhanced photocatalytic performance when compared with bare CaTiO3 NCs. The main roles of Au NPs in the enhanced photocatalytic mechanism of the Au@CaTiO3 composites manifest in the following aspects: (1) Au NPs act as excellent electron sinks to capture the photoexcited electrons in CaTiO3, thus leading to an efficient separation of photoexcited electron/hole pairs in CaTiO3; (2) the electromagnetic field caused by localized surface plasmon resonance (LSPR) of Au NPs could facilitate the generation and separation of electron/hole pairs in CaTiO3; and (3) the LSPR-induced electrons in Au NPs could take part in the photocatalytic reactions.

Surface‐enhanced Raman spectroscopy solution and solid substrates with built‐in calibration for quantitative applications

AbstractQuantitative analysis is a significant step forward for expanding the applications of surface‐enhanced Raman spectroscopy (SERS) in various fields. The reproducibility of the SERS measurement relies on the quality of the SERS substrates. Therefore, high enhancement SERS substrate with high uniformity and reproducibility is highly demanded for quantitative analysis. However, it remains a challenge to realize all the requirements of the SERS substrate. Here, we report 2 types (solution and solid) of SERS substrates with built‐in calibration for quantitative analysis. To prepare the substrates, high monodisperse Au@Ag nanocuboids (NCs) with internal standards trapped between the Au core and Ag shell are synthesized through the Au‐nanorod‐mediated method. It is demonstrated that at least 2 types of SERS tags can be trapped to synthesize the core‐internal standard‐shell (CISS) NCs. The SERS quantitative ability of the CISS NCs in solution is proved by detecting Rhodamine 6G, where a good linear relationship in a wide concentration range from 3 × 10−11 M to 1 × 10−8 M is achieved through the built‐in calibration. Besides the solution‐SERS substrate, CISS NCs are self‐assembled at the air–water interface to form uniform monolayer as the solid SERS substrate. SERS mapping reveals that the uniformity of the enhancement is improved through the built‐in calibration. The quantitative detection of concentration of Rhodamine 6G is achieved through the calibrated SERS mapping of the substrate. The internal and external enhancement factor calculation of the 2 types of SERS substrates indicates the promising method to further improve the reliability of the SERS analysis.

In situ electrochemically generated composite-type CoOx/WOx in self-activated cobalt tungstate nanostructures: implication for highly enhanced electrocatalytic oxygen evolution

The in situ electrochemical surface oxidation and associated disordered phenomenon under anodic condition are closely correlated with the electrocatalytic activities of cobalt-based compounds towards oxygen evolution reaction (OER). Herein, we report the interesting observations on this phenomenon in electrocatalytic systems of the cobalt tungstate (CoWO4) nanostructures and demonstrate the in situ oxidation and self-activation-induced amorphous reactive state determine their OER performances. The CoWO4 nanoflakes (NFs) with poor crystallinity are easily oxidized to composite-type CoOx/WOx and exhibit the best OER performance. To obtain a catalytic current density of 10mAcm−2, the CoWO4 NFs afford an overpotential as low as 436mV in an alkaline medium, which compare favorably to most previously reported Co-containing OER elecrocatalysts; whereas the catalytic current density of the crystalline CoWO4 nanorods (NRs) and CoWO4 nanocuboids (NCs) cannot reach 10mAcm−2 even at the high potential of 1.90V (vs. RHE). The in-depth mechanistic investigations demonstrate the excellent electrochemical OER behaviors of CoWO4 NFs are mainly originated from the in situ oxidation induced local structure change and amorphization.

Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction

Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611}high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

Plasmonic core-shell nanoparticles for SERS detection of the pesticide thiram: size- and shape-dependent Raman enhancement.

We systematically investigated the size- and shape-dependent SERS activities of plasmonic core-shell nanoparticles towards detection of the pesticide thiram. Monodisperse Au@Ag nanocubes (NCs) and Au@Ag nanocuboids (NBs) were synthesized and their Ag shell thickness was precisely adjusted from ∼1 nm to ∼16 nm. All these nanoparticles were used as SERS substrates for thiram detection, and the Raman intensities with three different lasers (514 nm, 633 nm and 782 nm) were recorded and compared. Our results clearly show that: (1) the excitation wavelength discriminated particle shapes regardless of particle sizes, and the maximized Raman enhancement was observed when the excitation wavelength approaches the SERS peak (provided there is significant local electric field confinement on the plasmonic nanostructures at that wavelength); (2) at the optimized laser wavelength, the maximum Raman enhancement was achieved at a certain threshold of particle size (or silver coating thickness). By exciting particles at their optimized sizes with the corresponding optimized laser wavelengths, we achieved a detection limit of roughly around 100 pM and 80 pM for NCs and NBs, respectively.

Large-Scale Self-Assembly and Stretch-Induced Plasmonic Properties of Core–Shell Metal Nanoparticle Superlattice Sheets

We report on a facile interfacial self-assembly approach to fabricate large-scale metal nanoparticle superlattice sheets from nonspherical core–shell nanoparticles, which exhibited reversible plasmonic responses to repeated mechanical stretching. Monodisperse Au@Ag nanocubes (NCs) and Au@Ag nanocuboids (NBs) could be induced to self-assembly at the hexane/water interface, forming uniform superlattices up to at least ∼13 cm2 and giving rise to mirror-like reflection. Such large-area mirror-like superlattice sheets exhibited reversible plasmonic responses to external mechanical strains. Under stretching, the dominant plasmonic resonance peak for both NB and NC superlattice sheets shifted to blue, following a power-law function of the applied strain. Interestingly, the power-law exponent (or the decay rate) showed a strong shape dependence, where a faster rate was observed for NB superlattice sheets than that for NC superlattice sheets.

Promoter Induced Rapid Synthesis of Hollow Silica Nano Cuboids from Octadecyltrichloro Silane

Promoter Induced Rapid Synthesis of Hollow Silica Nano Cuboids from Octadecyltrichloro Silane

Broadband absorption and efficiency enhancement of an ultra-thin silicon solar cell with a plasmonic fractal

We report in this work that quantum efficiency can be significantly enhanced in an ultra-thin silicon solar cell coated by a fractal-like pattern of silver nano cuboids. When sunlight shines this solar cell, multiple antireflection bands are achieved mainly due to the self-similarity in the fractal-like structure. Actually, several kinds of optical modes exist in the structure. One is cavity modes, which come from Fabry-Perot resonances at the longitudinal and transverse cavities, respectively; the other is surface plasmon (SP) modes, which propagate along the silicon-silver interface. Due to the fact that several feature sizes distribute in a fractal-like structure, both low-index and high-index SP modes are simultaneously excited. As a whole effect, broadband absorption is achieved in this solar cell. Further by considering the ideal process that the lifetime of carriers is infinite and the recombination loss is ignored, we demonstrate that external quantum efficiency of the solar cell under this ideal condition is significantly enhanced. This theoretical finding contributes to high-performance plasmonic solar cells and can be applied to designing miniaturized compact photovoltaic devices.