High-Efficiency Poly(Vinylidene Fluoride-Co-Hexafluoropropylene) Loaded 3D Marigold Flower-Like Bismuth Tungstate Triboelectric Films for Mechanical Energy Harvesting and Sensing Applications.

Triboelectric nanogenerators (TENGs) are one of the most trending energy harvesting devices because of their efficient and simple mechanism in harvesting mechanical energy from the environment into electricity. Herein, ferroelectric and dielectric bismuth tungstate (Bi2 WO6 (BWO)) with a marigold flower-like structure is prepared via a hydrothermal method, which is embedded in poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), forming a PVDF-HFP/BWO composite polymer film (CPF) to fabricate TENGs. Generally, the ferroelectric materials exhibit a large piezoelectric coefficient, high electrostatic dipole moment, and high dielectric constant. The prepared PVDF-HFP/BWO CPF reveals a high polar crystalline ß-phase which leads to enhanced piezoelectric and ferroelectric properties of the CPF, thus resulting in the increased electrical performance of the fabricated TENG. The electrical output performance of the proposed TENG is systematically investigated by varying the amount of BWO material embedded in the PVDF-HFP polymer. The fabricated PVDF-HFP/2.5 wt% BWO CPF-based TENG device exhibits the highest electrical output performance. Additionally, the robust test of the TENG device is conducted to investigate the electrical performance for long-term durability and mechanical stability. Finally, the proposed TENG is operated as a self-powered sensor, harvesting mechanical energy from daily life human activities, and powering various low-power portable electronics.

How to avoid a negative shift in reflection-type surface plasmon resonance biosensors with metallic nanostructures.

We experimentally demonstrate that introduction of a dielectric film can prevent the surface plasmon resonance (SPR) curve from being shifted to a smaller angle, called negative shift, which occurs unpredictably when metallic nanostructures deposited on a metal film are exposed to an adsorption of binding analytes. From parylene coating experiments, we find that the proposed reflection-type SPR system with a low refractive index MgF2 film and gold nanorods can provide an enhanced sensitivity by more than 6 times as well as a reliable positive shift. It is due to the fact that use of a dielectric film can contribute to the compensation of an anomalous dispersion relation and the prevention of a destructive interaction of propagating surface plasmons with multiple localized plasmon modes. Our approach is intended to show the feasibility and extend the applicability of the proposed SPR system to diverse biomolecular reactions.

Transmittance enhancement of sapphires with antireflective subwavelength grating patterned UV polymer surface structures by soft lithography.

We report the total and diffuse transmission enhancement of sapphires with the ultraviolet curable SU8 polymer surface structures consisting of conical subwavelength gratings (SWGs) at one- and both-side surfaces for different periods. The SWGs patterns on the silicon templates were transferred into the SU8 polymer film surface on sapphires by a simple and cost-effective soft lithography technique. For the fabricated samples, the surface morphologies, wetting behaviors, and optical characteristics were investigated. For theoretical optical analysis, a rigorous coupled-wave analysis method was used. At a period of 350 nm, the sample with SWGs on SU8 film/sapphire exhibited a hydrophobic surface and higher total transmittance compared to the bare sapphire over a wide wavelength of 450-1000 nm. As the period of SWGs was increased, the low total transmittance region of < 85% was shifted towards the longer wavelengths and became broader while the diffuse transmittance was increased (i.e., larger haze ratio). For the samples with SWGs at both-side surfaces, the total and diffuse transmittance spectra were further enhanced compared to the samples with SWGs at one-side surface. The theoretical optical calculation results showed a similar trend to the experimentally measured data.

Broadband and wide-angle distributed Bragg reflectors based on amorphous germanium films by glancing angle deposition.

We fabricated the distributed Bragg reflectors (DBRs) with amorphous germanium (a-Ge) films consisted of the same materials at a center wavelength (λc) of 1.33 µm by the glancing angle deposition. Their optical reflectance properties were investigated in the infrared wavelength region of 1-1.9 µm at incident light angles (θ inc) of 8-70°, together with the theoretical analysis using a rigorous coupled-wave analysis simulation. The two alternating a-Ge films at the incident vapor flux angles of 0 and 75° were formed as the high and low refractive index materials, respectively. The a-Ge DBR with only 5 periods exhibited a normalized stop bandwidth (∆λ/λ c) of ~24.1%, maintaining high reflectance (R) values of > 99%. Even at a high θ inc of 70°, the ∆λ/λ c was ~21.9%, maintaining R values of > 85%. The a-Ge DBR with good uniformity was obtained over the area of a 2 inch Si wafer. The calculated reflectance results showed a similar tendency to the measured data.

Label-Free Surface-Enhanced Raman Spectroscopy Biosensor for On-Site Breast Cancer Detection Using Human Tears.

Surface-enhanced Raman scattering (SERS) is an ultrasensitive molecular screening technique with greatly enhanced Raman scattering signals from trace amounts of analytes near plasmonic nanostructures. However, research on the development of a sensor that balances signal enhancement, reproducibility, and uniformity has not yet been proposed for practical applications. In this study, we demonstrate the potential of the practical application for detecting or predicting asymptomatic breast cancer from human tears using a portable Raman spectrometer with an identification algorithm based on multivariate statistics. This potentiality was realized through the fabrication of a plasmonic SERS substrate equipped with a well-aligned, gold-decorated, hexagonal-close-packed polystyrene (Au/HCP-PS) nanosphere monolayer that provided femtomole-scale detection, giga-scale enhancement, and <5% relative standard deviation for reliability and reproducibility, regardless of the measuring site. Our results can provide a first step toward developing a noninvasive, real-time screening technology for detecting asymptomatic tumors and preventing tumor recurrence.

Paper-Based Surface-Enhanced Raman Spectroscopy for Diagnosing Prenatal Diseases in Women.

We report the development of a surface-enhanced Raman spectroscopy sensor chip by decorating gold nanoparticles (AuNPs) on ZnO nanorod (ZnO NR) arrays vertically grown on cellulose paper (C). We show that these chips can enhance the Raman signal by 1.25 × 107 with an excellent reproducibility of <6%. We show that we can measure trace amounts of human amniotic fluids of patients with subclinical intra-amniotic infection (IAI) and preterm delivery (PTD) using the chip in combination with a multivariate statistics-derived machine-learning-trained bioclassification method. We can detect the presence of prenatal diseases and identify the types of diseases from amniotic fluids with >92% clinical sensitivity and specificity. Our technology has the potential to be used for the early detection of prenatal diseases and can be adapted for point-of-care applications.

Multifunctional microstructured polymer films for boosting solar power generation of silicon-based photovoltaic modules.

We propose two-dimensional periodic conical micrograting structured (MGS) polymer films as a multifunctional layer (i.e., light harvesting and self-cleaning) at the surface of outer polyethylene terephthalate (PET) cover-substrates for boosting the solar power generation in silicon (Si)-based photovoltaic (PV) modules. The surface of ultraviolet-curable NOA63 MGS polymer films fabricated by the soft imprint lithography exhibits a hydrophobic property with water contact angle of ∼121° at no inclination and dynamic advancing/receding water contact angles of ∼132°/111° at the inclination angle of 40°, respectively, which can remove dust particles or contaminants on the surface of PV modules in real outdoor environments (i.e., self-cleaning). The NOA63 MGS film coated on the bare PET leads to the reduction of reflection as well as the enhancement of both the total and diffuse transmissions at wavelengths of 300-1100 nm, indicating lower solar weighted reflectance (RSW) of ∼8.2%, higher solar weighted transmittance (TSW) of ∼93.1%, and considerably improved average haze ratio (HAvg) of ∼88.3% as compared to the bare PET (i.e., RSW ≈ 13.5%, TSW ≈ 86.9%, and HAvg ≈ 9.1%), respectively. Additionally, it shows a relatively good durability at temperatures of ≤160 °C. The resulting Si PV module with the NOA63 MGS/PET has an enhanced power conversion efficiency (PCE) of 13.26% (cf., PCE = 12.55% for the reference PV module with the bare PET) due to the mainly improved short circuit current from 49.35 to 52.01 mA, exhibiting the PCE increment percentage of ∼5.7%. For light incident angle-dependent PV module current-voltage characteristics, superior solar energy conversion properties are also obtained in a broad angle range of 10-80°.

Multifunctional nanoparticles: recent progress in cancer therapeutics.

Although much progress has been made in treating cancers, cancer death rates in and around the United States are still high. Current treatments are either ineffective against some cancers or detrimental to patients, which decreases their quality of life. The use of nanotechnology in cancer therapy can potentially increase patient survival, reduce side effects, and reduce mortality rates because nanoparticles (NPs) have the potential to target only tumors and bypass healthy cells. NPs possess many features, including size, shape, charge, and composition, which allow them to carry chemotherapeutics to cancer cells. NPs can also be used in radiotherapy as radiosensitizers and in imaging as contrast agents. Many studies have performed in vitro and/or in vivo experiments on these particles in human and animal cell lines. This review discusses recent studies on different NPs and their potential use in cancer therapy.

Imaging and curcumin delivery in pancreatic cancer cell lines using PEGylated α-Gd2(MoO4)3 mesoporous particles.

Mesoporous particles are emerging as multifunctional biomaterials for imaging and drug delivery in several disease models, including cancer. We developed PEGylated α-Gd2(MoO4)3 marigold flower-like mesoporous particles for the purpose of drug delivery and, more specifically, evaluated their ability to deliver curcumin. The obtained mesoporous particles significantly conjugated the curcumin particles on their surfaces by inducing the formation of curcumin nanoparticles. In vitro studies of the PEGylated mesoporous particles filled with curcumin demonstrated that these particles could considerably facilitate the continuous and sustained release of curcumin into the cytoplasm and nucleus. As a result, the intracellular release of curcumin can inhibit proliferation in two human pancreatic cancer cell lines: MIA PaCa-2 and PANC-1. Additionally, the particles showed the increased inhibition of pIKKα, pIKKα/ß and NF-κB-DNA binding activity as compared to pure curcumin. The curcumin conjugated mesoporous particles are concentrated in the cytoplasm and nucleus of the treated cancer cell lines. Consequently, these mesoporous particles are an effective method for drug delivery that can cross the biological barriers of the body targeting the cellular nucleoplasm.