Here, highly transparent nanocomposite films with an adjustable refractive index were fabricated through stable dispersion of ZrO2 (n = 2.16) nanoparticles (NPs) subjected to surface modification with SiO2 (n = 1.46) in polydimethylsiloxane (PDMS) (n = 1.42) using the Stöber method. ZrO2 NPs (13.7 nm) were synthesized using conventional hydrothermal synthesis, and their surface modification with SiO2 (ZrO2@SiO2 NPs) was controlled by varying the reaction time (3–54 h). The surface modification of the NPs was characterized using Fourier-transform infrared spectroscopy, dynamic light scattering, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and ellipsometry. The surface modification was monitored, and the effective layer thickness of SiO2 varied from 0.1 nm to 4.2 nm. The effective refractive index of the ZrO2@SiO2 NPs at λ = 633 nm was gradually reduced from 2.16 to 1.63. The 100 nm nanocomposite film was prepared by spin-coating the dispersion of ZrO2@SiO2 NPs in PDMS on the coverslip. The nanocomposite film prepared using ZrO2@SiO2 NPs with a reaction time of 18 h (ZrO2@SiO2-18h-PDMS) exhibited excellent optical transparency (Taverage = 91.1%), close to the transparency of the coverslip (Taverage = 91.4%) in the visible range, and an adjustable refractive index (n = 1.42–1.60) as the NP content in the film increased from 0 to 50.0 wt%.
The purpose of this study is to identify the difference in firm performance and employment growth between successful and failed capital procurement through equity-based crowdfunding. We conduct an empirical analysis using entire crowdfunding projects that attempted to raise capital through equity-based crowdfunding in South Korea in 2016. We summarize our findings as follows. Descriptive statistics show that the survival rate, sales growth rate, profitability growth, absolute employment growth, and employment growth rate of companies with successful crowdfunding are higher than those of companies with failed crowdfunding. However, from the difference analysis, we do not find a significant difference in the survival rate, sales growth rate, and profitability growth between companies with crowdfunding success and companies with crowdfunding failure. We find that the absolute employment growth and employment growth rate are significantly higher for companies that succeeded in crowdfunding projects compared to companies that did not. In this study, we find that the characteristics of these firms that are conducting or verifying new projects through equity-based crowdfunding financing are similar to those of prior studies results confirming the short-term effects of entrepreneurial activities or new business activities on economic performance and employment growth. In particular, it is very meaningful to confirm that the direct effect of employment growth is also found in start-up firms that raise capital through equity-based crowdfunding. By investigating the difference in firm performance and employment outcomes according to the results of equity-based crowdfunding investment, this study provides useful insights to investors for their efforts to validate participation in crowdfunding. Also, our study raises important policy implications for regulators in their efforts to resolve unemployment and the lack of capital problem for startups and new businesses.
Solar-to-steam (STS) generation based on plasmonic materials has attracted significant attention as a green method for producing fresh water. Herein, a simple in situ method is introduced to fabricate Au nanoparticles (AuNPs) on cellulose filter papers as dual-functional substrates for STS generation and surface-enhanced Raman spectroscopy (SERS) sensing. The substrates exhibit 90% of broadband solar absorption between 350 and 1800 nm and achieve an evaporation rate of 0.96 kg·m−2·h−1 under 1-sun illumination, room temperature of 20 °C, and relative humidity of 40%. The STS generation of the substrate is stable during 30 h continuous operation. Enriched SERS hotspots between AuNPs endow the substrates with the ability to detect chemical contamination in water with ppb limits of detection for rhodamine 6G dye and melamine. To demonstrate dual-functional properties, the contaminated water was analyzed with SERS and purified by STS. The purified water was then analyzed with SERS to confirm its purity. The developed substrate can be an improved and suitable candidate for fresh water production and qualification.
Polymer nanocomposites, prepared by incorporating functional nanoparticles (NPs) into a polymer matrix, have advantages of utilizing functionalities of polymers and NPs. Among them, transparent high-refractive-index polymer nanocomposites (THPNs), prepared by incorporating highly refractive NPs into polymer matrices, are advantageous for effectively manipulating light. This review focuses on the introduction of fabrication of THPN prepared by incorporating inorganic-oxide NPs, especially zirconia (ZrO 2 ), and its characteristics as an optical material. ZrO 2 NPs have a high refractive index and high transmittance in visible light regions with high and narrow optical bandgap energy. Since ZrO 2 NPs are harmless to humans and physically and chemically stable, they are suitable for applications of advanced optical materials for display and energy devices. Various fabrication methods of THPN with ZrO 2 NPs and surface modifications of ZrO 2 NPs to prevent agglomeration are introduced. Principles and specific applications, which THPN could work with and for, are introduced as well.
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