The Golden Fig: A Plasmonic Effect Study of Organic-Based Solar Cells

An optimization work on dye-sensitized solar cells (DSSCs) based on both artificial and natural dyes was carried out by a fine synthesis work embedding gold nanoparticles in a TiO2 semiconductor and perfecting the TiO2 particle sizes of the scattering layer. Noble metal nanostructures are known for the surface plasmon resonance peculiarity that reveals unique properties and has been implemented in several fields such as sensing, photocatalysis, optical antennas and PV devices. By embedding gold nanoparticles in the mesoporous TiO2 layer and adding a scattering layer, we were able to boost the power conversion efficiency (PCE) to 10.8%, using an organic ruthenium complex. The same implementation was carried out using a natural dye, betalains, extracted from Sicilian prickly pear. In this case, the conversion efficiency doubled from 1 to 2% (measured at 1 SUN illumination, 100 mW/cm2 under solar simulation irradiation). Moreover, we obtained (measured at 0.1 SUN, 10 mW/cm2 under blue light LED irradiation) a record efficiency of 15% with the betalain-based dye, paving the way for indoor applications in organic natural devices. Finally, an attempt to scale up the system is shown, and a betalain-based- dye-sensitized solar module (DSSM), with an active area of 43.2 cm2 and a PCE of 1.02%, was fabricated for the first time.

Enhancement of Schottky Junction Silicon Solar Cell with CdSe/ZnS Quantum Dots Decorated Metal Nanostructures

Recently, in the solar energy society, several key technologies have been reported to meet a grid parity, such as cost-efficient materials, simple processes, and designs. Among them, the assistive plasmonic of metal nanoparticles (MNPs) integrating with the downshifting on luminescent materials attracts much attention. Hereby, Si-based Schottky junction solar cells are fabricated and examined to enhance the performance. CdSe/ZnS quantum dots (QDs) with different gold nanoparticles (Au NPs) sizes were incorporated on a Si light absorbing layer. Due to the light scattering effect from plasmonic resonance, the sole Au NPs layer results in the overall enhancement of Si solar cell’s efficiency in the visible spectrum. However, the back-scattering and high reflectance of Au NPs lead to efficiency loss in the UV region. Therefore, the QDs layer acting as a luminescent downshifter is deployed for further efficiency enhancement. The QDs layer absorbs high-energy photons and re-emits lower energy photons in 528 nm of wavelength. Such a downshift layer can enhance the overall efficiency of Si solar cells due to poor intrinsic spectral response in the UV region. The optical properties of Au NPs and CdSe QDs, along with the electrical properties of solar cells in combination with Au/QD layers, are studied in depth. Moreover, the influence of Au NPs size on the solar cell performance has been investigated. Upon decreasing the diameters of Au NPs, the blueshift of absorbance has been observed, cooperating with QDs, which leads to the improvement of the quantum efficiency in the broadband of the solar spectrum.

Synthesis and Near-Field Enhancement of Composite Nanoarrays Based on Electrodeposition and in Situ Reaction

Since the morphology and element composition of metal nanostructures strongly affect the surface plasma oscillation characteristics, it has been widely concerned in surface enhanced Raman scattering (SERS). Herein, we proposed a novel route to fabricate composite Au/Ag nanoparticle arrays with synergistic effect for electromagnetic enhancement. Ag nanoparticles were electrodeposited onto a home-made template with highly ordered bowl-like pits. After a novel method of “confined annealing”, we further achieved well-regulated spherical Ag NP arrays, and the composite Au/Ag nanoparticle arrays were finally obtained via in situ replacement. The fabricated composite nanostructures showed stable and sensitive surface enhanced Raman scattering (SERS) performance mainly due to the synergistic effect and abundant “hot spots”, with the enhancement factor (EF) of [Formula: see text] for crystal violet (CV) molecules. In addition, this simple and effective preparation process greatly improved the uniformity of three-dimensional nanostructures, providing a new idea for further improving the stability of SERS signals.

Enhancing SERS Intensity by Coupling PSPR and LSPR in a Crater Structure with Ag Nanowires

The sensitive characteristics of surface-enhanced Raman scattering (SERS) can be applied to various fields, and this has been of interest to many researchers. Propagating surface plasmon resonance (PSPR) was initially utilized but, recently, it has been studied coupled with localized surface plasmon resonance that occurs in metal nanostructures. In this study, a new type of metal microstructure, named crater, was used for generating PSPR and Ag nanowires (AgNWs) for the generation of LSPR. A crater structure was fabricated on a GaAs (100) wafer using the wet chemical etching method. Then, a metal film was deposited inside the crater, and AgNWs were uniformly coated inside using the spray coating method. Metal films were used to enhance the electromagnetic field when coupled with AgNWs to obtain a high SERS intensity. The SERS intensity measured inside the crater structure with deposited AgNWs was up to 17.4 times higher than that of the flat structure with a deposited Ag film. These results suggest a new method for enhancing the SERS phenomenon, and it is expected that a larger SERS intensity can be obtained by fine-tuning the crater size and diameter and the length of the AgNWs.

Effect of Silver Nanoparticles on Fluorescence Intensity of Fluoreseina Dye Mixed in One Solution

Metal enhanced fluorescence (MEF) is an unequaled phenomenon of metal nanoparticle surface plasmons, when light interacts with the metal nanostructures (silver nanoparticles) which result electromagnetic fields to promote the sensitivity of fluorescence. This work endeavor to study the influence of silver nanoparticles on fluorescence intensity of Fluoreseina dye by employment mixture solution with different mixing ratio. Silver nanoparticles had been manufactured by the chemical reduction method so that Ag NP layer coating had been done by hot rotation liquid method. The optical properties of the prepared samples (mixture solution of Fluoreseina dye solutions and colloidal solution with 5 minutes prepared of Ag NPs) tested by using UV-VIS absorption and Fluorescence spectrophotometer. by using AFM, SEM testes, the structure of silver nanoparticles had been estimated. the result of this work showed that adding Ag NPs colloidal to Fluoreseina dye solution help get a significant increase in the fluorescence intensity of this dye. this study results show that its significant to recent related studies in MEF.

Methionine controlled impediment of secondary nucleation leading to nonclassical growth within self-assembled de novo gold nanoparticles

The conventional key steps for seed mediated growth of noble metal nanostructures involve classical and nonclassical nucleation. Furthermore, the surface of the seed catalytically enhances the secondary nucleation involving Au+ to Au0reduction, thus providing in-plane growth of seed. In contrast to this well-established growth mechanism, herein we report the unique case of methionine (Met) controlled seed mediated growth reaction, which rather proceeds via impeding secondary nucleation in presence of citrate stabilized gold nanoparticle (AuNP). The interaction between the freshly generated Au+ and thioether group of Met in the medium restricts the secondary nucleation process of further seed catalyzed Au+ reduction to Au0. This incomplete conversion of Au+, as confirmed by X-ray photoelectron spectroscopy (XPS), results in a significant enhancement of the zeta (z) potential even at low Met concentration. Nucleation of in situgenerated small-sized particles (nAuNPs) takes place on the parent seed surface followed by their segregation from the seed. Self-assembly process of these nAuNPs arises from the aurophilic interaction among the Au+. Furthermore, the time dependent growth of smaller particles to larger sized particles through assembly and merging within the same self-assembly validates the non-classical growth. This strategy has been successfully extended towards the seed mediated growth reaction of AuNP in presence of three bio-inspired decameric peptides having varying number of Met residues. The study confirms the nucleation strategy even in presence of single Met residue in the peptide and also the self-assembly of nucleated particles with increasing Met residues within the peptide.

Pre-Clinical and Clinical Applications of Small Interfering RNAs (siRNA) and Co-Delivery Systems for Pancreatic Cancer Therapy

Pancreatic cancer (PC) is one of the leading causes of death and is the fourth most malignant tumor in men. The epigenetic and genetic alterations appear to be responsible for development of PC. Small interfering RNA (siRNA) is a powerful genetic tool that can bind to its target and reduces expression level of a specific gene. The various critical genes involved in PC progression can be effectively targeted using diverse siRNAs. Moreover, siRNAs can enhance efficacy of chemotherapy and radiotherapy in inhibiting PC progression. However, siRNAs suffer from different off target effects and their degradation by enzymes in serum can diminish their potential in gene silencing. Loading siRNAs on nanoparticles can effectively protect them against degradation and can inhibit off target actions by facilitating targeted delivery. This leads to enhanced efficacy of siRNAs in PC therapy. Moreover, different kinds of nanoparticles such as polymeric nanoparticles, lipid nanoparticles and metal nanostructures have been applied for optimal delivery of siRNAs that are discussed in this article. This review also reveals that how naked siRNAs and their delivery systems can be exploited in treatment of PC and as siRNAs are currently being applied in clinical trials, significant progress can be made by translating the current findings into the clinical settings.