Encapsulation of Single Plasmonic Nanoparticles within ZIF‐8 and SERS Analysis of the MOF Flexibility

Hybrid nanostructures composed of metal nanoparticles and metal‐organic frameworks (MOFs) have recently received increasing attention toward various applications due to the combination of optical and catalytic properties of nanometals with the large internal surface area, tunable crystal porosity and unique chemical properties of MOFs. Encapsulation of metal nanoparticles of well‐defined shapes into porous MOFs in a core–shell type configuration can thus lead to enhanced stability and selectivity in applications such as sensing or catalysis. In this study, the encapsulation of single noble metal nanoparticles with arbitrary shapes within zeolitic imidazolate‐based metal organic frameworks (ZIF‐8) is demonstrated. The synthetic strategy is based on the enhanced interaction between ZIF‐8 nanocrystals and metal nanoparticle surfaces covered by quaternary ammonium surfactants. High resolution electron microscopy and tomography confirm a complete core–shell morphology. Such a well‐defined morphology allowed us to study the transport of guest molecules through the ZIF‐8 porous shell by means of surface‐enhanced Raman scattering by the metal cores. The results demonstrate that even molecules larger than the ZIF‐8 aperture and pore size may be able to diffuse through the framework and reach the metal core.     

The capability of SnTe QDs as QDSCs working in the visible–NIR region and the effects of Eu-doping on improvement of solar cell parameters

The current work is the first effort to show the capability of SnTe quantum dots (QDs) in as a quantum dots solar cell device, which work in visible-near-infrared (NIR) regions, and improvement of the solar cell parameters by Eu-doping. Undoped and Eu-doped SnTe QDs with different Eu concentration from 2 to 6% were synthesized by a co-precipitation method. X-ray diffraction patterns and transmission electron microscopy images indicated that, crystallite and particle size of the samples were decreased by increasing of Eu content. Fourier-transform infrared (FTIR) and Raman spectroscopy results revealed that some vibration modes were appeared and disappeared by Eu-doping. According to the photoluminescence (PL) results, PL intensity of the doped sample was enhanced significantly in the green region in comparison to the PL intensity of the undoped sample. Ultraviolet-visible-near infrared spectroscopy results indicated that the pristine and Eu(2%)-doped samples don’t have any absorption in the visible region, while, Eu(4% and 6%)-doped SnTe QDs showed a good absorption in this region. Photocurrent measurements showed that, unlike the pristine and Eu(2%)-doped QDs, Eu(4% and 6%)-doped SnTe QDs showed a high responsivity in the visible and NIR regions. Solar cell measurements showed that, solar cell parameters such as short current density (J_sc), open circuit voltage (V_oc), conversion efficiency values (η), and fill factor (FF) were increased by Eu-doping.     

Highly dispersible and uniform size Cu2ZnSnS4 nanoparticles for photocatalytic application

Highly dispersible, uniform size (～7 nm) single-phase Cu₂ZnSnS₄ nanoparticles have been synthesized by hydrothermal method using non-toxic surfactant (oleic acid). High resolution transmission electron microscopy image indicates good crystallinity of the Cu₂ZnSnS₄ nanoparticles with the growth along (1 1 2) plane. X-ray photoelectron spectroscopy analyses suggested that the formation of with Cu, Zn, and Sn in +1, +2 and +4 oxidation states. The optical absorption spectrum of Cu₂ZnSnS₄ nanoparticles exhibits an absorption in the visible region and its optical band gap was found to be ～1.72 eV, which could be much more appropriate for photocatalytic application under visible light irradiation. These Cu₂ZnSnS₄ nanoparticles have been shown high photocatalytic degradation activity of methylene blue (MB) dye in the presence of visible light irradiation. The rate constant (k) value of Cu₂ZnSnS₄ nanoparticles is found to be 0.0144 min^?1. We have discussed the mechanism of dye degradation process that drives the photocatalytic degradation process. The reusability of the Cu₂ZnSnS₄ nanoparticles for the dye degradation is also demonstrated.     

Effect of polyaniline concentration on the photoconversion efficiency of nano-TiO<Subscript>2</Subscript> based dye sensitized solar cells

Extensive research have been made in improving the dye sensitized solar cells (DSSC) performance by designing, tailoring and enhancing the photoconversion properties of the matrix. The approaches used are material synthesis, dye permutation combinations, use of natural extracts or using several sensitizers. The polymers are also being explored in this regards in their pristine or composite forms. Therefore, in this study an attempt is made to synthesize a mesoporous polyaniline–titanium dioxide (PANI–TiO₂) nanocomposites with one pot synthesis approach at different concentrations of PANI (0.3–0.7 ml). Titanium isopropoxide was used as precursor for TiO₂ with aniline and the material was synthesized at ice bath temperature. Morphological observations showed that the composite is a mesoporous material with tubular structure where TiO₂ particles are seen entrapped in the polymer matrix and found that intercalation can be tailored with PANI concentration. Structural, functional and optical characterization indicate anatase phase of TiO₂, with several functional bands that can help in dye interaction and broad absorption bands within visible region. The photocurrent-voltage response was measured with simulated light and source-meter. It is interesting to note that increasing PANI concentration enhances the mesoporous structure and hence increases the dye loading capacity and photoconductivity of the material. The efficiency increased by about 22 % with addition of 0.5 ml of PANI from 0.3 ml. The proposed study has indicated that such material have the potential to be used for DSSC fabrication with which the device performance can further be increased to a better levels.     

Interaction of Glycylglycine with Cationic Surfactants—Cetylpyridinium Chloride and Cetylpyridinium Bromide: A Volumetric,Ultrasonic and Conductometric Study

The interactions of glycylglycine (di-peptide of glycine) also known as 2-[(2-aminoacetyl)amino] acetic acid with cationic surfactants cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) as a function of temperature in aqueous medium has been studied by well-know permutation of volumetric, ultrasonic and conductometric techniques. These measurements have been used to evaluate some useful thermodynamic parameters viz. apparent molar volumes, \( \phi_{v} \), partial molar volumes, \( \phi_{v}^{o} \), transfer volumes, \( \phi_{\text{v}}^{0} (tr) \), partial molar expansibility, \( \phi_{E}^{0} \), hydration number, n_H, apparent molal compressibility, \( \phi_{K} \), limiting partial molal adiabatic compressibility, \( \phi_{K}^{0} \). The specific conductivity (κ) was used to calculate the critical micellar concentration (cmc) and other physicochemical parameters of micellization of CPC/CPB with glycylglycine. The critical micelle concentration, cmc and limiting molar conductivity, \( \varLambda_{m}^{o} \) of the two surfactant systems were determined by using the conductivity data at 298.15 K, 303.15 K, 308.15 K and 313.15 K. The acquired data have been discussed as per various interactions taking place in the ternary system of CPC/CPB, glycylglycine and water.     

MUC1 aptamer-conjugated mesoporous silica nanoparticles effectively target breast cancer cells

In the present study, we developed aptamer (Apt) conjugated mesoporous silica nanoparticles (MSNs) for specific delivery of epirubicin (EPI) to breast cancer cells. MSNs were synthesized and functionalized with 3-mercaptopropyltrimethoxysilane (3-MPTMS), followed by MUC1 aptamer conjugation through disulfide bonds. The nanoparticles were analyzed by transmission electron microscopy (TEM), particle size analyzer, zeta potential, elemental analysis (CHNS), aptamer conjugation efficiency, drug loading efficiency, and drug release profile. Cell uptake and in vitro cytotoxicity of different formulations were performed. The results of MSNs characterization confirmed spherical nanoparticles with thiol functional groups. Particle size of obtained nanoparticles was 163?nm in deionized water. After conjugation of MUC1 aptamer and EPI loading (MSN-MUC1-EPI), particle size increased to 258?nm. The aptamer conjugation to MSNs with disulfide bonds were confirmed using gel retardation assay. Cellular uptake studies revealed better cell uptake of MSN-MUC1-EPI compared to MSN-EPI. Moreover, cytotoxicity study results in MCF7 cell lines showed improved cytotoxicity of MSN-MUC1-EPI in comparison with MSN-EPI or EPI at the same concentration of drug. These results exhibited that MSN-MUC1-EPI has the potential for targeted drug delivery into MUC1 positive breast cancer cells to improve drug efficacy and alleviate side effects.     

Design and Synthesis of Waterborne Polyurethanes

Waterborne polyurethanes (WBPUs) have attracted increasing attention in a wide range of industrial applications because of their versatile properties as well as ecofriendly nature. Although extensive research has been carried out on WBPU synthesis, the roles of some of the key synthesis components remain unclear. In this study, through systematically controlling and fine tuning the precursor compositions and reaction conditions, over 300 WBPUs are synthesized. This research enables the roles of several key components that govern WBPU physicochemical properties and ultimately the potential WBPU applications to be identified. Using hair styling as an example, it is demonstrated that only the WBPUs with an optimal range of properties (e.g., Young's modulus >150 MPa, elongation at break: 15–300%, moisture uptake <10%) can achieve strong styling performance. To further improve the natural‐feel sensory benefits in the final styling products, a number of fatty acids with different carbon chain lengths or unsaturation levels are incorporated into WBPUs. Among the ten fatty acids studied, linoleic acid is identified as the most preferred additive. Both in vitro and in vivo testing demonstrate that WBPUs with optimal properties are promising materials for developing strong, long‐lasting styling products with natural feel.     

Effect of ageing on the morphology and creep and recovery of polymer-modified bitumens

Polymer additives are used to improve the properties of road bitumens including their oxidative resistance. However, their usage as anti-oxidative materials remains relatively unclear. This study aims to investigate the changes in the morphology and the rheological response of polymer modified bitumens used in road pavement construction caused by ageing. An elastomer (radial styrene butadiene styrene, SBS) and a plastomer (ethyl vinyl acetate, EVA) polymer were mixed with one base bitumen at three polymer concentrations. The bitumens were RTFO and PAV aged. The morphology of the bitumens was captured by fluorescence microscopy while the rheological properties were measured by means of the multiple stress creep and recovery (MSCR) test. The results show that the morphology of the SBS modified bitumen degrades with ageing as a function of polymer concentration and dispersion, with higher dispersion being more resistant. The morphology of the EVA modified bitumen has a low ageing susceptibility irrespective of polymer concentration. The MSCR response of EVA modified bitumens does not differ from that found for unmodified bitumen, where the hardening produces a decrease in the non-recoverable compliance. In the case of SBS modified bitumen, the degradation of the polymer backbone affects the bitumen hardening as much as the polymer phase dispersed and networked in the bitumen phase. Furthermore, in the case of the elastomer, the average percent recovery is in agreement with the variation of the morphology with ageing. Therefore, the use of the average percent recovery as a valuable rheological index of the integrity of the polymer network can be advocated.     

Raman investigation of air-stable silicene nanosheets on an inert graphite surface

The fascinating properties of two dimensional (2D) crystals have gained increasing interest for many applications. The synthesis of a 2D silicon structure, namely silicene, is attracting great interest for possible development of next generation electronic devices. The main difficulty in working with silicene remains its strong tendency to oxidation when exposed to air as a consequence of its relatively highly buckled structure. In this work, we univocally identify the Raman mode of air-stable low-buckled silicene nanosheets synthesized on highly oriented pyrolytic graphite (HOPG) located at 542.5 cm?1. The main focus of this work is Raman spectroscopy and mapping analyses in combination with ab initio calculations. Scanning tunneling microscopy images reveal the presence of a patchwork of Si three-dimensional (3D) clusters and contiguous Si areas presenting a honeycomb atomic arrangement, rotated by 30° with respect to the HOPG substrate underneath, with a lattice parameter of 0.41 ± 0.02 nm and a buckling of the Si atoms of 0.05 nm. Raman analysis supports the co-existence of 3D silicon clusters and 2D silicene. The Raman shift of low-buckled silicene on an inert substrate has not been reported so far and it is completely different from the one calculated for free-standing silicene and the ones measured for silicene grown on Ag(111) surfaces. Our experimental results are perfectly reproduced by our ab initio calculations of deposited silicene nanosheets. This leads us to conclude that the precise value of the observed Raman shift crucially depends on the strain between the silicene and the HOPG substrate.

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