Titanium Nitride Nanoparticles as Plasmonic Solar Heat Transducers

We demonstrate that lossy plasmonic resonances of nanoparticles are broad enough to cover the majority of the solar spectrum and highly efficient for absorbing sunlight. In analytical calculation, we choose a titanium nitride nanoparticle as a lossy plasmonic nanoresonator and present that sunlight absorption efficiency of a titanium nitride nanoparticle is higher than gold and even black carbon nanoparticles. The experiments demonstrate that titanium nitride nanoparticles dispersed in water have high efficiency to heat water and generate vapor than carbon nanoparticles by converting sunlight into heat. Our results open great possibilities for efficient solar heat applications with titanium nitride nanoparticles

A Microfluidic Quantitative Polymerase Chain Reaction Method for the Simultaneous Analysis of Dozens of Antibiotic Resistance and Heavy Metal Resistance Genes

This study developed, optimized, and demonstrated a microfluidic quantitative polymerase chain reaction (MF-qPCR) method for the simultaneous quantification of 39 antibiotic resistance genes (ARGs), five heavy metal resistance genes, three genes encoding the integrase of three different classes of integrons, and 16S rRNA genes (used as a measure of total bacterial biomass). Because the volume of the template is much smaller with MF-qPCR (a few nanoliters) than with conventional qPCR, a preamplification step was needed to improve the sensitivity and the limits of quantification of the MF-qPCR method to be similar to those of conventional qPCR. The MF-qPCR method was successfully demonstrated on untreated municipal wastewater, treated municipal wastewater, and drinking water samples. The treated municipal wastewater samples had higher concentrations of all genes compared to those in the drinking water samples. Similarly, the untreated municipal wastewater samples had higher concentrations for all but one of the targeted genes compared to those in the treated municipal wastewater samples. The MF-qPCR method established in this study provides highly accurate quantitative information about numerous ARGs and other genes from environmental samples

Examining the Performance of Refractory Conductive Ceramics as Plasmonic Materials: A Theoretical Approach

The main aim of this study is to scrutinize promising plasmonic materials by understanding their electronic structure and correlating them to the optical properties of selected refractory materials. For this purpose, the electronic and optical properties of the conductive ceramics TiC, ZrC, HfC, TaC, WC, TiN, ZrN, HfN, TaN, and WN are studied systematically by means of first-principles density functional theory. A full <i>ab initio</i> procedure to calculate plasma frequency from the electronic band structure is discussed. The dielectric functions are calculated by including electronic interband and intraband transitions. Our calculations confirm that transition metal nitrides, such as TiN, ZrN, and HfN, are the strongest candidates, exhibiting performance comparable to that of conventional noble metals in the visible to the near-infrared regions. On the other hand, carbides are not suitable for plasmonic applications because they show very large losses in the same regions. From our calculated dielectric functions, the scattering and absorption efficiencies of nanoparticles made of these refractory materials are evaluated. It is revealed that TiN and TaC are the best candidate materials for applications in photothermal energy conversion over a broad spectral region. Furthermore, quality factors for localized surface plasmon resonance and surface plasmon polaritons are calculated to compare quantitative performances, and ZrN and HfN are found to be comparable to conventional plasmonic metals such as silver and gold

All-Ceramic Microfibrous Solar Steam Generator: TiN Plasmonic Nanoparticle-Loaded Transparent Microfibers

A portable and reusable solar water distillation structure based on low cost ceramic materials is developed. The structure is made of ceramic fiber wool (CW) and titanium nitride nanoparticles (TiN NPs) that are chemically immobilized to the CW. When sunlight illuminates the structure, the TiN NPs absorb sunlight while unnecessary heating of the remaining water is suppressed by the CW. The CW effectively supply water by capillary force such that the TiN NPs are always kept close to the water surface. It yields a solar thermal conversion efficiency of more than 80% at 100 mW cm^–2 that is much more efficient than the conventional systems. Our structures can be used as eco-friendly and efficient solar water distillator

Hybridizing Poly(ε-caprolactone) and Plasmonic Titanium Nitride Nanoparticles for Broadband Photoresponsive Shape Memory Films

Plasmonic nanoparticles can confine light in nanoscale and locally heat the surrounding. Here we use titanium nitride (TiN) nanoparticles as broadband plasmonic light absorbers and synthesized a highly photoresponsive hybrid cross-linked polymer from shape memory polymer poly­(ε-caprolactone) (PCL). The TiN–PCL hybrid is responsive to sunlight and the threshold irradiance was among the lowest when compared with other photoresponsive shape memory polymers studied previously. Sunlight heating with TiN NPs can be applied to other heat responsive smart polymers, thereby contributing to energy-saving smart polymers research for a sustainable society

Hot Electron Excitation from Titanium Nitride Using Visible Light

One major strategy that has been used to inject carriers into wide-band-gap materials involves exciting hot carriers from a nanostructured metal using low-energy photons. Here, we demonstrate that titanium nitride (a conductive ceramic) can be used as an alternative for photoexciting hot carriers. Planar samples that form titanium nitride/zinc oxide/titanium nitride trilayers are fabricated, and the generation of photocurrent using visible light is confirmed. The photocurrent obtained by using titanium nitride is much larger than that obtained by using gold in a similar structure. Our results will therefore facilitate the use of titanium nitride, which is robust and inexpensive, in harvesting the visible region of the solar spectrum in photovoltaics and photocatalysis

Water Quality Monitoring and Risk Assessment by Simultaneous Multipathogen Quantification

Water quality monitoring and microbial risk assessment are important to ensure safe water for drinking, recreational, and agricultural purposes. In this study, we applied a microfluidic quantitative PCR (MFQPCR) approach to simultaneously quantify multiple waterborne pathogens in a natural freshwater lake in Hokkaido, Japan, from April to November, 2012. Tens of thousands of geese stopped over at this lake during their migration in spring and fall. Because lake water is used for irrigation of the surrounding agricultural area, we assessed infection risks through irrigation water usage based on pathogen concentrations directly measured by MFQPCR. We detected various pathogens in the lake water, particularly during the bird migration seasons, suggesting that migratory birds were the main source of the pathogens. However, neither counts of geese nor fecal indicator bacteria were good predictors of pathogen concentrations. On the basis of quantitative microbial risk assessment, concentrations of <i>Campylobacter jejuni</i> and <i>Shigella</i> spp. in water samples were above the concentrations that can potentially cause 10^–4 infections per person per year when water is used to grow fresh vegetables. These results suggest that direct and simultaneous multipathogen quantification can provide more reliable and comprehensive information for risk assessment than the current fecal indicator-based approach

Application of a Microfluidic Quantitative Polymerase Chain Reaction Technique To Monitor Bacterial Pathogens in Beach Water and Complex Environmental Matrices

Microfluidic quantitative polymerase chain reaction (MFQPCR) and conventional quantitative polymerase chain reaction methods were compared side by side in detecting and quantifying 19 genetic markers associated with <i>Escherichia coli</i> and select bacterial pathogens in algae, beach sand, and water from Lake Michigan. Enteropathogenic <i>E. coli</i> (EPEC), Shiga toxin-producing <i>E. coli</i>, <i>Salmonella</i> spp., <i>Campylobacter jejuni</i>, and <i>Clostridium perfringens</i> were among the pathogens tested. Of the pathogenic markers, <i>eaeA</i> that encodes intimin in EPEC was detected in all sample types: water (5%), detached/floating algae (42%), exposed/stranded algae (43%), sand below exposed algae (27%), and nearshore sand with no algae (22%). Other pathogenic markers, however, were detected sporadically. Despite comparable results from the two methods for the genetic markers tested in this study, the MFQPCR method may be superior, with the advantage of detecting and quantifying multiple pathogens simultaneously in environmental matrices

Experimental Evidence for in Situ Nitric Oxide Production in Anaerobic Ammonia-Oxidizing Bacterial Granules

Although nitric oxide (NO) emissions from anaerobic ammonium oxidation (anammox)-based processes were reported previously, the NO production pathways are poorly understood. Here, we investigated the NO production pathways in anammox granules in detail by combining ¹⁵N-stable isotope tracer experiments with various inhibitors, microsensor measurements, and transcriptome analysis for key genes of NO₂^– reduction. NO was emitted from the anammox granules, which account for 0.07% of the N₂ emission. ¹⁵N-stable isotope-tracer experiments indicated that most of the N₂ was produced by anammox bacteria, whereas NO was produced from NO₂^– reduction by anammox and denitrifying bacteria. The NO emission rate was highest at pH 8.0 and accelerated by increasing NH₄⁺ and NO₂^– concentrations in the culture media. The microsensor analyses showed the <i>in situ</i> NO production rate was highest in the outer layer of the anammox granule where anammox activity was also highest. The detected <i>in situ</i> NO concentrations of up to 2.7 μM were significantly above physiological thresholds known to affect a wide range of microorganisms present in wastewater. Hence, NO likely plays pivotal roles in the microbial interactions in anammox granules, which needs to be further investigated

Plasmonic–Photonic Hybrid Modes Excited on a Titanium Nitride Nanoparticle Array in the Visible Region

Conventionally used plasmonic materials generally have low thermal stability, low chemical durability (except gold), and are incompatible with complementary metal–oxide semiconductor processes. However, titanium nitride (TiN), an emerging plasmonic material, possesses gold-like optical properties, but displays relatively large ohmic losses. We fabricated a periodic array of TiN nanoparticles to effectively reduce these losses by coupling the localized surface plasmon resonance with light diffraction. The height of the nanoparticle and the periodicity of the array were designed to match the excitation conditions of both the localized surface plasmon resonance and light diffraction. As a result, the array supported a plasmonic–photonic hybrid mode in the visible region. For the loss mitigation effect to be assessed, photoluminescence (PL) from the light emitting layer on the array was measured. The PL intensity was larger than that from the same layer on a TiN thin film, demonstrating reduced loss. The angular and spectral profiles of the PL could be controlled by the hybrid mode. Our results thus pave the way toward plasmonic devices that can be fabricated using traditional complementary metal–oxide semiconductor processes