bluuebunny/crossref_metadata_2025 huggingface dataset:
Nano-Structured Pd-Sn Catalysts for Alcohol Electro-Oxidation in Alkaline Medium
Authors: Zalineeva Anna , Serov Alexey , Padilla Monica , Martinez Ulises , Artyushkova Kateryna , Baranton Stève , Coutanceau Christophe , Atanassov Plamen
Published: February 2020

The study of alcohols electrooxidation is of paramount importance not only for direct fuel cell and/or electrolysis cell applications, but also in order to gain the fundamental knowledge on reaction mechanisms for electrosynthesis applications.

Tin is known to be a high performance co-catalyst of noble metal for alcohol oxidation, particularly concerning the ethanol electrooxidation reaction in acidic medium.  This property of tin in association with palladium was recently confirmed for the electrooxidation of methanol, ethanol, and ethylene glycol in alkaline medium.

Here, the electrocatalytic behavior of Pd1Snxcatalysts towards the electrooxidation of different C1, C2 and C3 alcohols is compared and discussed in terms of activity and reaction pathways: methanol and ethylene glycol since they are the simplest alcohol and polyol, respectively, ethanol and glycerol because they can both be produced from biomass, and isopropanol which only bears a secondary alcohol function, because it can be interesting for the development of “rechargeable” direct fuel cells.  

Particularly, the occurrence of two possible mechanisms, a base-catalyzed one and a mechanism based on the ability of the catalytic surface to favor the adsorption and desorption of species at low potentials, is discussed, as well as the difference in activity comparing isopropanol and glycerol oxidation reactions.

For this purpose, active self-supported Pd1Snx catalysts are synthesized by the Sacrificial Support Method (SSM). Their catalytic activity towards the oxidation of C1 to C3 alcohols was determined in alkaline medium. The comparison of the activity allowed discarding a first base catalyzed deprotonation reaction of alcohols as rate determining step (rds), and spoke up for a mechanism involving a C-adsorption of carbon bearing an alcohol function. By comparing isopropanol and glycerol oxidation voltammograms, and on the basis of in situFTIR spectroscopy measurements, it has been shown that desorption of dihydroxyacetone could be the limiting step for glycerol oxidation at low potentials.

Acknowledgement: Anna Zalineeva thanks the Center for Emerging Energy Technologies, Farris Engineering Center (UNM) for assistance and technical support, and the County Council of Poitou-Charentes (France) for financial support.
Electrochemical Reduction of Carbon Dioxide on Silver Nanostructures and the Role of Oxygen
Authors: Jee Michael Shincheon , Min Byoung Koun , Hwang Yun Jeong
Published: February 2020

Current energy production habits deplete fossil fuels and accumulate atmospheric CO2 which contribute to the global climate change. Electrochemical fuel production via CO2 reduction reaction is an idealistic, yet an achievable process that mitigates CO2 emissions and simultaneously satisfies energy demands. Here, the enhancement of CO2 reduction activity and stability on size-controlled particulate silver electrocatalysts derived from a simple, one-step cyclic voltammetry (CV) process by changing scan rates (1–200 mV/s) was demonstrated. Interestingly, larger nanoparticles prepared by slower scan rates (1–5 mV/s) have exhibited the most degree of enhancement for CO2 reduction to CO product. Compared to untreated silver foil, nanostructured silver electrode has shown an anodic shift of approximately 200 mV in the onset potential of CO partial current density (j
CO), 160 mV reduction of overpotential at j
CO = 10 mA/cm2, and increased Faradaic efficiency (F.E.) for CO production especially at lower biased potentials (−0.89–−1.19 V vs. RHE). Stability tests have demonstrated a drastic improvement in maintaining CO F.E. X-ray photoelectron spectroscopy suggests that the enhancement is associated with stable oxygen species incorporated on the nanoparticle Ag surfaces during the CV fabrication process.

Figure 1
Electrochemical Studies of Thin Films of Side-Chain Ferrocene-Containing Diblock Copolymers
Authors: Ito Takashi , Ghimire Govinda , Yi Yi , Derylo Maksymilian A , Baker Lane A
Published: February 2020

This presentation will report the electrochemical properties of gold-supported thin films of polystyrene-poly(2-(acryloyloxy)ethyl ferrocenecarboxylate) diblock copolymers (PS-b-PAEFc) with different PAEFc volume fractions (f
PAEFc = 0.47, 0.30, 0.17).  These polymers were synthesized by two-step atomic transfer radical polymerization.  Thin PS-b-PAEFc films were prepared on planar gold substrates via spin-coating from their toluene solutions.  Atomic force microscopy images of the resulting films showed the formation of PAEFc microdomains with different (lamellar, cylindrical and spherical) morphologies as anticipated from the volume fractions.  Their electrochemical properties including the percentages of reactive ferrocene moieties and electron propagation efficiency (apparent diffusion coefficients) were assessed using cyclic voltammetry (CV) and chronocoulometry in 0.1 M TBAPF6/CH3CN.  CV data showed redox peaks from the PAEFc moieties.  PS-b-PAEFc (f
PAEFc = 0.47, 0.30) exhibited an increase in redox current with increasing film thickness, whereas PS-b-PAEFc (f
PAEFc = 0.17) showed a similar current regardless film thickness.  This observation suggests (1) the redox reaction took place at PAEFc microdomains that direct contacted to the electrode surface; (2) relatively thick (> 50 nm) films of PS-b-PAEFc (f
PAEFc = 0.47, 0.30) comprised PAEFc microdomains penetrating across the films; (3) the CH3CN-swollen PS and PAEFc were permeable for counter anions so that the charge neutrality was satisfied upon the oxidation of the ferrocene moieties.  The apparent diffusion coefficients in these films were small (in the order of 10-11 cm2/s), probably limited by the diffusion of counter ions and/or by inefficient electron propagation between adjacent ferrocene moieties within the PAEFc microdomains.  Applications of electrode-supported PS-b-PAEFc films will also be presented.   

Reference

G. Ghimire, Y. Yi, M. A. Derylo, L. A. Baker, T. Ito, manuscript in preparation.
Novel Electrocatalysts for Generating Oxygen from Acid Water Electrolysis
Authors: Chatterjee Kuntal , Wu Jingjie , Shen Jianfeng , Hackenberg Ken , Vajtai Robert , Lou Jun , Ajayan Pulickel M
Published: February 2020

Rapidly increasing global energy demand and developing carbon-neutral economy impose great challenge to the scientific community and it requires untiring efforts to exploit and store abundant but diffuse renewable energy sources. One innovative and promising approach for that is the efficient production of hydrogen serving as fuel, through electricity-driven water splitting. However, the overall efficiency of the reaction is largely impeded by the kinetically sluggish oxygen evolution reaction (OER), imposing serious overpotential requirement. Therefore, an efficient oxygen evolution catalyst is essential to enhance the reaction rate and/ or lower the overpotential. Although precious metal oxides, such as RuO2 and IrO2, are considered to be the most active OER electrocatalysts, they are not suitable for large-scale applications because of their scarcity and high costs. So There is an ongoing interest to find earth-abundant and inexpensive electrocatalysts for OER. In response, non-noble transition-metal-based oxides, layered double hydroxides (LDH), perovskite-type metal oxides are some of the advance electrocatalyst candidates with their own limitations.

Here, for the first time, we focus on layered transition metal dicalchogenides (TMDs) like MoS2 and TaS2 in this search due to their natural abundance and high activity towards hydrogen evolution. We report MoS2 and TaS2, in both their 2H and 1T polymorphs that display excellent catalytic activity for OER in much required acid medium. They are chemically exfoliated to thinner nanosheets from MoS2 precursor and TaS2 nanostructures synthesized by chemical vapour deposition. Structural and electrochemical studies reveal their corresponding semiconducting 2H and metallic 1T polymorph and the impressive electrocatalytic performance respectively. The proliferation of active sites is such a high for those materials that an electrocatalytic current density of 10 mA cm−
2 is achievable with overpotential much lower than that of the benchmark IrO2 or RuO2OER catalyst. The Tafel slopes found for the different samples are also in good rivalry of the benchmark catalyst. The performances are also analyzed on the basis of their probable structure relation.

This work presents general strategies to grow nanostructures of layered TMD materials for the enhanced catalytic performance in OER and open up a new avenue in the pursuance of water splitting research towards the growth of hydrogen economy.
In-Situ TEM Study of Ba0.5Sr0.5Co0.8Fe0.2O3 for Oxygen Evolution Electrocatalysis
Authors: Han Binghong , Stoerzinger Kelsey A. , Tileli Vaso , Gamalski Andrew , Stach Eric A. , Shao-Horn Yang
Published: February 2020

Developing highly active catalysts for oxygen evolution reaction (OER) near room temperature is critical to improve the efficiency of many electrochemical technologies in the pursuit of sustainable energy, such as water splitting using light or electricity, and rechargeable metal-air batteries. Recently, many non-precious metal oxides have been developed as highly active OER catalysts, including many perovskite oxides (ABO3) of first-row transition metals such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ
(BSCF). Previous studies have shown that BSCF has good activity accompanied with surface amorphization in OER process. However, little in-situ study has been done to look into the reasons for its high activity and low stability. In this contribution, we use environmental transmission electron microscopy (ETEM) to investigate the surface atomic structure and chemistry evolution of BSCF in the presence of H2O. Significant breathing-like structural oscillation has been observed on BSCF, which is closely related to the electron beam and H2O vapor applied onto the BSCF. Electron energy loss spectra (EELS) implied an electron-beam induced OER on BSCF during breathing motions. This allowed us to observe in-situ BSCF during OER under the TEM, to better understand the incorporation of H2O into the BSCF structure and the surface amorphization of BSCF in OER process, which might involve the O2 generation not only on the surface but also in the near-surface layers of BSCF. This work provides a deeper insight into the stability and active site of oxides catalysts for OER.
Tuning the Composition and Structure of Metallic Nanotubes for Electrocatalysis
Authors: Papandrew Alexander B. , Atkinson Robert W. , St. John Samuel , Unocic Raymond R , Zawodzinski Thomas A.
Published: February 2020

Recent trends in the design of electrocatalysts for power generation systems have highlighted the usefulness of supportless extended surfaces, surface-segregated alloys, and shape-controlled particles for activity enhancement1.  Multiple synthetic schemes have been devised to produce these materials with varying degrees of versatility and scalability. 

            We have investigated templated vapor deposition as an addition to the already wide array of synthetic strategies, and applied these methods to problems in low-temperature electrocatalysis.  In our approach, metalorganic precursors are used to deposit conformal nanoparticulate films within the internal channels of porous anodic alumina templates.  By sequentially depositing multiple species, layered structures can be formed.  Subsequent thermal treatments can then be used to drive crystallite growth, alloying (or phase separation) and mesostructural evolution.  The template structure is then dissolved to release high-aspect ratio nanotubes that can be implemented as electrocatalysts (Figure 1).

            By rationally selecting the constituent metals, relative compositions, and heat treatment temperatures, we synthesized highly active electrocatalysts for multiple reactions of technological interest.  These include the use of pure Pt nanotubes2 for acidic oxygen reduction, Bi-decorated Pd nanotubes for formic oxidation, Pt-Ru nanotubes for methanol oxidation3and, recently, Ru-Pt nanotubes for hydrogen oxidation in alkaline electrolytes.

            In this contribution we examine the unique characteristics of the novel class of electrocatalysts emerging from our templated vapor deposition methods.  Comprehensive characterization of the catalysts using chemical and structural probes including advanced transmission electron microscopy are used to gain insight into the structure-property relationships governing nanotube activity.  Finally, future prospects for the synthesis of additional functional nanostructures for electrochemical systems will be discussed.

References

1 M. K. Debe, Nature 486, 43–51 (2012).

2 A. B. Papandrew, R. W. Atkinson, G. a. Goenaga, S. S. Kocha, J. W. Zack, B. S. Pivovar, and T. A. Zawodzinski, J. Electrochem. Soc. 160, F848–F852 (2013).

3 R. W. Atkinson, R. R. Unocic, K. A. Unocic, G. M. Veith, T. A. Zawodzinski, and A. B Papandrew, ACS Appl. Mater. Interfaces DOI: 10.1021/am508228b (2015).

Figure 1
Aligning Silicon Nanopillar Formed in Electroless HF/H2O2 Etching through Pre-Forming Porous Layer
Authors: Chiang C. -C. , Xu Dawei , Huang Y.-C , Juan P.- C. , Lo F. -S. , Hu Hui-Qin , He Cheng-Long , Lee T. -H.
Published: February 2020

For fabricating a controllable nanopillar array structure by utilizing the metal-assisted etching technique, we created a fine porous cladding layer on the surface of bulk silicon to settle down silver nanoparticles.

Prior to metal-assisted etching process, a 10nm thick porous silicon layer was produced on the surface of a p-type, 1-10 Ohm-cm, (100) bulk silicon by HF based electrochemically etching and then rinsed by D.I. water. After spin-drying, the specimen and a same silicon specimen but without the porous layer were dipped in a solution (HF / AgNO3 / H2O) for 30 seconds for the nucleation of silver nanoparticles. The dipped specimens were then etched by HF/ H2O2/ H2O solution for forming nanopillar.

Through the observation of Field Emission Scanning Electronic Microscopy (FE-SEM), we found the pores on the surface of the porous layer could provide priority nucleation sites for silver nanoparticles. Hence, we could achieve a designed silicon nanopillar array by controlling the formation of the porous layer. After etching, the silicon specimen with the pre-forming porous layer exhibits different characteristic from the one without the layer as shown in figure.

Figure 1
Platinum-Based Alloy and Ionic Liquid Composites Dispersed on Carbon Black As a Synergistic Catalyst for Oxygen Reduction Reaction
Authors: Tran Quoc-Chinh , Choi Ho-Suk
Published: February 2020

Catalysts for oxygen reduction are of great interest in the field of renewable energy technology such as fuel cell, which can provide the power for future electric vehicles. Herein, we report a one-pot synthesis of composite material consisting of platinum(Pt)-based alloy and ionic liquid dispersed on carbon black (SuperP) in 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide through using one atmospheric pressure plasma. The PtNi-NPs with the size of 2–3 nm were stably and uniformly hybridized on the surface of carbon blacks, which were also covered with ionic liquid layer. The incorporation of PtNi alloy with a hydrophobic and protic ionic liquid layer shows good electrocatalytic activity due to the high O2 solubility of the ionic liquid, resulting in high frequency and high mass activity of oxygen reduction reaction (ORR), which is better than that of commercial Pt/C catalysts. The PtNiRu-ionic liquid/carbon black catalyst (Figure 1) also shows better stability than the commercial Pt/C under the same ORR condition as seen in Figure 2. The results prove that the Pt-based alloy and ionic liquid composites dispersed on carbon black push the ORR towards completion and can indeed be one of promising candidates for many electrochemical catalytic applications.

Figure 1
Efficient and Stable Silicon-Based Solar Water Splitting Devices
Authors: Oh Jihun
Published: February 2020

Hydrogen production by solar water splitting has attracted considerable interests as a long-term energy storage system (ESS) to store intermittent solar energy to stable and reusable chemical fuels. While silicon is a promising material for photoelectrochemical (PEC) water splitting because of an earth-abundancy, low cost, and small bandgap, silicon has slow kinetics for hydrogen evolving reaction (HER). In addition, under conditions for oxygen evolution reaction, silicon easily forms an insulating SiO2 or even corrodes. Therefore, new strategies are requires for stable and efficient silicon based PEC water splitting devices. In this talk, I’ll present our efforts to develop a silicon-based solar water splitting devices, leveraging the existing Si photovoltaic technology. Particularly, I’ll talk about nanoporous black Si to improve HER. In addition, I’ll present our novel device architecture to enhanced OER stability.
Plasmon-Mediated Surface Chemistry for Solar Photocatalysis
Authors: Wei Wei David
Published: February 2020

Using sunlight to facilitate and promote valuable chemical reactions is an ideal solution to the challenge of meeting future energy demands.  Our group aims to address fundamental questions concerning surface plasmon resonance (SPR)-mediated interfacial electron transfer (ET) and photothermal heating in order to develop new materials and strategies for efficiently converting solar energy to chemical energy.  In this talk, I will show how we unambiguously reveal the mechanics of plasmon-mediated electron transfer (PMET) in Au/TiO2 heterostructures under visible light (λ > 515 nm) during in situ operation.  I will further discuss how we directly probe the relaxation dynamics and energetics of the transferred “effective hot electrons” that participate in photocatalytic reactions.  I will explore some strategies for manipulating “hot electrons” for the rational design and construction of a new class of multi-component solar photocatalysts for efficiently producing H2 from water.
Solar to Fuels Conversion By a Monolithic and Standalone Photoelectrochemical Device
Authors: Jeon Hyo Sang , Hwang Yun Jeong , Min Byoung Koun
Published: February 2020

Solar to fuels conversion inspired from nature has attracted substantial attention due to a demand for developing sustainable future energy as well as chemical resources. In this presentation, I will introduce our strategy for a highly efficient solar energy to chemical conversion device using CO2 and water as feedstock. For the realization of this architecture we developed a thin film photovoltaic technology for the light absorbing component using a low cost, solution based Cu(InxGa1-x)(SySe1-y)2 (CIGS) fabrication method to provide high enough potential for the conversion reactions. Our solar-fuel device also adapted metal oxide nanoparticle deposited with a low temperature coating method as the water oxidation catalyst and nanostructured metal films as the CO2 reduction to CO or HCOOH generation catalyst. Remarkably, this is the first demonstration of a monolithic and standalone solar-fuel device whose solar-to-fuel conversion efficiency from CO2 and H2O is over 4%, which is comparable to that of photosynthesis in nature. The details of the synthetic method and characterization of each component and the solar-fuel generation system are discussed. Also, some prospects of solar-fuel research for achieving highly efficient solar-fuel production device will be suggested.
Electronic Band Structure and Charge Transfer in Semiconductors
Authors: Wu Nianqiang , Cushing Scott Kevin
Published: February 2020

Semiconductor has been widely used in photocatalytic and photovoltaic devices. The electronic band structure governs the charge separation, charge migration and charge recombination processes.  This talk provides an insight into the band gap, the deep and shallow level states in the band gap and the surface trap states that play important roles in the processes of photo-generated charge carriers in the metal oxide semiconductors. Also, this talk demonstrates how to engineer the bulk band structure and the surface states in order to enhance the solar energy conversion.
Rational Design of Semiconductor for Photoelectrochemical Water Splitting
Authors: Wei Su-Huai
Published: February 2020

The search for semiconducting materials for commercially viable photoelectrochemical (PEC) water splitting has been extremely challenging. Meeting that challenge requires the engineering of a semiconductor with the following tightly coupled material property criteria: appropriate band gap (1.6 – 2.2 eV), efficient visible light absorption, high carrier mobility, correct band edge positions that straddle the water redox potentials, and durability in solution environment. In this talk, I will discuss some general strategies for the rational design of semiconductors to simultaneously meet the requirements for a high efficiency solar-driven PEC water splitting devices. Density functional theory (DFT) calculations reveal that with appropriate donor-acceptor pairs or acceptor-acceptor co-incorporation, anatase TiO2 holds great potential for a viable PEC device. Other approaches to modify the band structure of TiO2, such as the application of strain and band structure engineering of other materials such as CoX2O4 and BiVO4, will also be discussed.
Developing Catalysts for the Selective Electrochemical Reduction of Carbon Dioxide to C2 and C3 Products
Authors: Yeo Boon Siang
Published: February 2020

The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons and alcohols using copper catalysts is a promising way to produce valuable carbon fuels and chemical feedstocks. However, the selectivity for this process is still rather poor. Here, we present our recent efforts to develop Cu-based catalysts for the electroreduction of CO2 to target molecules such as ethylene, ethanol, and propanol. In the case of CO2 reduction to ethylene and ethanol, we found that their faradaic yields can be systematically tuned by changing the thickness of the deposited Cu2O overlayers. 1.7-3.6 μm thick films exhibited the best selectivity for these C2 compounds at -0.99 V vs. RHE, with faradaic efficiencies of 34-39% for ethylene and 9-16% for ethanol. Less than 1% methane was formed. A high C2H4/CH4 products’ ratio of up to ~100 could be achieved. Scanning electron microscopy, X-ray diffraction and in-situ Raman spectroscopy revealed that the Cu2O films reduced rapidly and remained as metallic Cu0 particles during the CO2 reduction. The selectivity trends exhibited by the catalysts during CO2 reduction in phosphate buffer and KHCO3 electrolytes suggest that an increase in local pH at the surface of the electrode is not the only factor in enhancing the formation of C2 products. An optimized surface population of edges and steps on the catalyst is also necessary to facilitate the dissociation of CO2 and the dimerization of the pertinent CHxO intermediates to ethylene and ethanol. We also demonstrate in this presentation the importance of defects in the formation of propanol from CO2 reduction.

Reference: Ren D, Deng Y, Handoko AD, Chen CS, Malkhandi S and Yeo BS. Selective Electrochemical Reduction of Carbon Dioxide to Ethylene and Ethanol on Copper (I) Oxide Catalysts. ACS Catal. 2015, 5, 2814-2821
Photocatalytic Reduction of CO2 to CO on TiO2-Passivated InP at High Underpotentials in Ionic Liquids
Authors: Zeng Guangtong , Cronin Stephen B.
Published: February 2020

Lowering the overpotential required to drive the photocatalytic reduction of CO2 to useful products is a very important challenge. In this article, we use an ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4) co-catalyst to improve the selectivity and efficiency of CO2 reduction to CO on TiO2-passivated InP. Here, the InP surface is passivated using a thin film of TiO2 deposited by atomic layer deposition (ALD), which improves the photoconversion efficiency by as much as 18X compared to bare InP (at -1.57V vs. NHE). We use a non-aqueous ionic liquid solution, which enables CO2 reduction with a Faradaic efficiency of 89% at an overpotential of 0.02V. More importantly, we observe CO2 reduction to CO at an underpotential of 0.68V with a Faradaic efficiency of 39%. We believe there are three mechanisms of enhancement in this photocatalytic system. Firstly, the TiO2 deposited by ALD is n-type due to oxygen vacancies and forms an np-junction with the underlying p-type InP photocathode. Secondly, the catalytically active sites on the TiO2 lower the reduction reaction energy barrier. Thirdly, the [EMIM]+ ions in solution further lowering the energy of CO2 intermediate, most likely by complexation
Development of New Photocatalysts for Solar-to-Fuel Conversion
Authors: Maeda Kazuhiko
Published: February 2020

Photocatalytic water splitting and CO2 fixation under visible light have attracted attention as potential means of solar-to-fuel energy conversion. Our group has studied such photocatalytic systems based on non-oxide type semiconductors such as oxynitrides and nitrides. As a representative example of our materials, zirconia-modified TaON exhibits the functionality as a hydrogen evolution photocatalyst in a Z-scheme water splitting system, in combination with a WO3-based oxygen evolution photocatalyst in the presence of an iodate/iodide redox couple. The apparent quantum efficiency of this system is ~6.3% at 420 nm, which is the highest record among photocatalytic water splitting systems reported so far. For visible-light-driven CO2 fixation, we have recently developed a composite material consisting of a polymeric carbon nitride semiconductor and a catalytic ruthenium(II) complex, which photocatalyzes CO2 reduction to formic acid under visible light. Importantly, isotope-labeling experiments showed that the products obtained during the reaction originate from not the decomposition of carbon nitride itself but CO2 used as the reactant. Optimizing the structure of the ruthenium complex led to an improvement in the performance, giving a high turnover number (>1000 for 20 hours), an apparent quantum yield of 5.7% (at 400 nm) and selectivity (>80%). These numbers are greatest among photocatalytic CO2 reduction systems reported so far. In this presentation, the details of such photosystems we have developed will be introduced.
Preparation of Nickel Tungstate (NiWO4) Nanoparticles and Characterization with Electrochemical Methods in Combination with Mott-Schottky Theory
Authors: Hosseini Seyyedamirhossein , Farsi Hossein , Moghiminia Shokoufeh , Li Zhihai
Published: February 2020

Nickel tungstate is an interesting semiconductor for application in solar cell owing to its low band gap1, high mechanical stability and abundant oxygen sites (4 oxygen/Ni-W) for dye molecule absorption. Nanoparticle nickel tungstate has been synthesized with different methods including solid state2, direct mechanical rout3 and standard ceramic rout4. In current study nickel tungstate has been synthesized with different particle size distribution using co-precipitation5 method (N1) and in microemulsion medium in presence of cetyltrimethylammonium bromide (CTAB) as surfactant (N2).

Synthesized samples were examined using XRD, TEM and DRS methods. Electrochemical impedance spectroscopy method in combination with mott-schottky theory has been applied for determination of electronic specification of all samples. Furthermore, light transformation efficiency of samples for application in solar cell has been studied using gratzel two-electrode cell.

Figure 1
Cost Effective Inkjet Printing of Titania Nanoparticles for Photocatalytic Applications
Authors: Bernasconi Roberto , Magagnin Luca
Published: February 2020

Titania is one of the most promising materials in the field of light induced catalysis on surfaces. In the last decades researchers investigated in particular applications like self-cleaning and photochemical degradation of pollutants. Moreover titania present antibacterial properties, which allows to consider uses in the biomedical field. The most immediate method to produce titania coatings is the anodization of a titanium substrate, which is able to provide good results in terms of quality and reproducibility. Alternative methods to employ titania when a titanium substrate cannot be provided have been developed as well, including TiO2 codeposition with metals, sol-gel deposition and inkjet printing. In particular inkjet printing of titania nanoparticles is of great interest due to the possibility of creating patterns in an easy and cheap way, controlling the thickness of the deposited layer with good accuracy. TiO2 inkjet printing has been attempted in the past mainly using laboratory printers, with good results in terms of photocatalytic and antimicrobial activity. Possible challenges for the future are the optimization of the method and the use of widely available office inkjet printers to increase the flexibility of the process.

The present work aims at depositing titania from a commercial office inkjet printer, modified to use custom made inks containing nanoparticles obtained by sol-gel synthesis. The nanoparticles of titania thus obtained are characterized via TEM to quantify the mean size and the diameters distribution. The subsequent formulation of the printing inks is done following the specifications of the corresponding pigmented inks used in standard printing on paper. In particular viscosity and surface tension are measured and modified to obtain the best printing quality. Finally the printed layers, either in form of continuous samples or patterns, are characterized from the morphological point of view and their photocatalytic efficiency is tested. Moreover, as preliminary results, the printed layers are tested on conductive substrates for electrophotocatalysis as well.
Nanomaterials-Based Biosensors for Biomedical and Food Safety Applications
Authors: Song Yang , Li He , Zhu Chengzhou , Du Dan , Lin Yuehe
Published: February 2020

Nanoparticles, graphene and graphene-like 2D nanomaterials have attracted tremendous research interest in the field of bioanalytical chemistry due to their intrinsic properties, including the electronic, optical, and mechanical properties associated with their nanostructures. The marriage of nanotechnology and biosensors has created many ingenious biosensing strategies for applications in the areas of biomedical diagnosis and food safety. In this talk, I will give an overview of the recent advances in the development of graphene and graphene-like 2 D nanomaterial-base biosensors and peroxidase-like bimetallic nanoparticles for biosensing.  Special attention will be paid to nanomaterials-based enzyme biosensors, immunosensors, and DNA biosensors. Future perspectives on high-performance nanomaterials-based biosensors in biomedical and food safety applications will be are discussed.
A Comparison of the Sensor Performance of Electrochemical Peptide-Based Sensors Fabricated from 6- or 11-Carbon Self-Assembled Monolayers
Authors: Sutlief Arin L , Lai Rebecca Y.
Published: February 2020

In this study, we compare the sensor performance of two electrochemical peptide-based (E-PB) sensors fabricated using peptide probes modified with a 6- or 11-carbon alkanethiol linker.  The biorecognition probe is a highly antigenic peptide sequence in the HIV-1 p24 antigen, and the target is the antibody generated against this antigen (anti-p24 antibody). When compared to the C11-based sensor, the C6-based sensor shows higher signal suppression in the presence of the correct target. In addition, the C6-based sensor is also regenerable and can be reused for over 3 times. Despite the reduced signaling capability and the lack of regenerability, the C11-based sensor is slightly more specific for the target antibody. While there are advantages and disadvantages associated with each of the two systems, with proper optimization, both sensors can potentially be used for real time detection of HIV infections.

Figure 1
Optimization of Phage and Surface Blocker Loading for the Magnetoelastic Biosensor
Authors: Hu Jiajia , Horikawa Shin , Wang Fengen , Chai Yating , Du Songtao , Liu Yuzhe , Chin Bryan A. , Hu Jing
Published: February 2020

This paper investigates the optimization of phage and surface blocker loading for the magnetoelastic (ME) biosensor that is being developed for real-time, direct pathogen detection on food surfaces. E2 phage with high binding affinity toward Salmonella Typhimurium was selected as a model bio-recognition element and tested along with five commercially available surface blocking reagents: BSA, StartingBlock, SuperBlock, Casein and BLOTTO (purchased from Thermo Fisher Scientific, Inc.). The effects of the concentration and loading time of these phage and surface blockers on biosensor performance were investigated. The concentrations of E2 phage and the surface blockers tested were 5×109, 5×1010, 5×1011 and 5×1012 vir/mL and 1×, 0.5× and 0.25×, respectively. In addition, various loading times were tested: 30, 60 and 90 min for E2 phage and 60 and 120 min for the blockers. To visualize and measure surface coverage, E2 phage was labeled with the Alexa Fluor 488 dye, whereas the blockers were each labeled with the Texas Red dye (purchased from Thermo Fisher Scientific, Inc.). After loading steps, fluorescence micrographs of biosensor surfaces were captured, followed by image processing (gray-scale conversion, background subtraction, and thresholding) to measure the surface coverage. Concentrations and loading times that yield the largest phage coverage and avoid over-coverage of the blockers were selected. Furthermore, comparisons among the blockers were conducted to select the best blocking reagent (i.e., SuperBlock for this investigation). These optimized loading conditions were then used to construct measurement sensors (with phage) and control sensors (without phage) for direct detection of S. Typhimurium on fresh apples. Both measurement and control sensors were placed on S. Typhimurium-spiked apple surfaces (1.0×106 CFU/mm2), and the sensors’ resonant frequency shifts were measured as a function of time using a surface-scanning coil detector. While the resonant frequency shifts of the control sensors remained negligible, those of the measurement sensors decreased largely as time elapsed, indicating that specific binding of S. Typhimurium on the measurement sensor had occurred. The frequency data were further analyzed statistically, and the detection was found to be realized in 15 minutes. Finally, scanning electron microscopy was used to confirm the specific binding of S. Typhimurium on the measurement sensors.
Wireless Sensors and Actuators Based on Magnetostrictive Resonators
Authors: Zhang Kewei , Zhang Lin , Cheng Z.-Y.
Published: February 2020

Biosensors based on magnetostrictive resonators, magnetostrictive cantilever and magnetostrictive particles (MSPs), have been developed in recent years [1]. Due to their magnetic nature, these biosensors are wireless, which makes them to a great candidate for in-situ detection. Both phage and antibody, which are immobilized onto the surface of the magnetostrictive resonator, have been used as biological molecular recognition elements. The performance characterization of these biosensors shows that these biosensors work well in liquid and exhibit a high sensitivity for the detection of bacteria in water [2].

It is well known that the sensitivity of MSP increases with reducing size of the MSP. Therefore, a much better sensitivity is expected for the MSPs with a smaller size. The above results demonstrate that the biosensors based on the magnetostrictive resonators are suitable for in-situ detection of pathogens in liquid media. To fully develop the detection technology based on magnetostrictive resonators for in-field detection, a small size interrogation unit/device is required. A new methodology was developed recently [3]. Based on this technology, a handheld device is developed to characterize the response of the biosensors based on magnetostrictive resonators.

For the detection of pathogenic species in food samples, sampling is always a key issue, since the locations of the target species are unknown and the biosensors have to be brought into reaction with the target species. It is experimentally found that an MSP biosensor can act as an actuator when it is driven under a frequency different than the resonant frequency.  In the experiments, it is found that the moving speed of the MSP actuator is dependent on the frequency. A freestanding MSP is an actuator that can move along its length direction without the limitation in displacement and the motion can be both directions.

REFERENCES

[1] K. W. Zhang, L. Zhang, L. L. Fu, S. Q. Li, H. Q. Chen, and Z.-Y. Cheng, Magnetostrictive resonators as sensors and actuators, Sensors & Actuators: A. Physical, 
200, 2-10 (2013).

[2] K. W. Zhang, L. L. Fu, L. Zhang, Z.-Y. Cheng, and T.-S. Huang, Magnetostrictive particle based biosensors for in-situ and real-time detection of pathogens in water, Biotechnology and Bioengineering, 111, 2229 (2014).

[3] Z.Y. Cheng, A.X. Zhang, K.W. Zhang, B.A. Chin, Systems for Characterizing Resonance Behavior of Magnetostrictive Resonator(s), U.S. Patent Application

No. 20120280682 (2012).
Novel Sensing System for in-Situ Monitoring Soil Water Content
Authors: Zhang Lin , Cheng Z.-Y.
Published: February 2020

Water shortage is a world-wide issue and currently 70% of global freshwater consumption is agriculture. Unfortunately, the water use in agriculture is often inefficient with only a fraction of the water diverted for agriculture effectively used in plant growth, with the rest lost via soil drainage, evaporation, or transpiration. Water efficiency in agriculture has been extensively researched. Conversion from traditional furrow irrigation to micro-irrigation methods has been shown to reduce irrigation needs for about 50% while improving yields. Universally applied micro-irrigation solutions many not realize improved yields due to different crop requirements and the high specificity of agriculture practices. Improving the efficient use of water still demands the development of new technologies that cost less and save energy by accurately assessing crop status for a given location, climate and soil condition. To reach this, it is critical to monitor the soil water content (SWC) or soil moisture in a real-time manner. 

Many technologies have been developed and are currently widely used to determine the SWC. Most of these technologies are stationary. That is, the soil samples have to be collected in the field and it is, then, immediately stored in a special bag to keep the moisture and delivered to a laboratory for the test. This is time consuming process and adds additional cost to the characterization of SWC. Technologies, such as time domain reflectometry, have the capability to determine the in-situ SWC in a real-time manner, but it is only for a localized spot. Therefore, it is very critical to find a right spot to perform the characterization/analysis, which is somehow arbitrary and requires trained personnel. For a farm land, many spots have to be analyzed to determine the average SWC for the farm land.

This work is designed to develop a rationally new technology that can monitor the average SWC over a farm land. The technology is for in-situ analysis and has the potential to be developed as a wireless network. A sensing system is designed and built to determine the average SWC over a farm land, as illustrated in Figure 1. A few spots (i.e., the corners and center of a farm land) are selected as the nodes, as shown in Figure 1 (a). At each node, an electrical pole (i.e., probe) will be installed as illustrated in Figure 1(b). Each probe contains a few electrodes which are located at different depths underground. The part of the electrical pole outside of soil is either an electronic deliver or electronic receiver. Two probes form a measuring sensor/system, such as contacting with a lock-in amplifier, which determines the average SWC over the area, as shown in Figure 2 (c and d). The system is tested in real farm land to determine the maximum area can be analyzed. Other commercial sensors are used to validate the sensor system for SWC determination.  

Figure 1 (a) Schematic of sensor networks for measuring SWC, (b) electrical pole, and two probes to form a measuring sensor: (c) top view and (d) side view.

Figure 1
Multilayer Scanning Coil Detector for Improved Detection of Surface Pathogen Contamination
Authors: Liu Yuzhe , Du Songtao , Horikawa Shin , Wikle Howard Clyde , Hu Jiajia , Wang Fengen , Chin Bryan A.
Published: February 2020

This paper presents an investigation into improved pathogen detection on food and food contact surfaces using a multilayer scanning coil detector combined with wireless magnetoelastic (ME) biosensors. In contrast to our previous studies of surface pathogen detection where a single-layer planar coil was employed, a more sensitive detector with a multi-layer coil design was investigated in this work. The two-fold roles of the coil detector are: (1) the application of an alternating magnetic field for the excitation of the ME sensor’s vibration and (2) detection of the resultant magnetic flux changes induced by the vibrating sensor. Surface pathogen detection can then be realized when the sensor comes into contact and binds specifically with the pathogen of interest, causing the sensor’s resonant frequency to decrease. For surfaces with large roughness and curvatures (e.g., leafy greens and cantaloupes), a long stand-off distance (distance between the sensor and detector) may be required. Hence, enhancement in the excitation power and sensitivity of coil detector with a multilayer design is a key to improving the system’s detection capabilities. Furthermore, smaller ME biosensors with higher mass sensitivity can also be measured with this sensitive multilayer coil detector. Several design parameters, including the number of layers, width, height, and spacing of coil turns, were studied. Coils were fabricated using standard microelectronic fabrication techniques (photolithograpy, electroplating, etching and sputtering) and tested.Both theoretical calculations and experimental data showed that the above coil geometric parameters have a significant impact on the signal amplitude and stand-off distance. Finally, with the newly fabricated multilayer coil detector, simultaneous measurement of multiple biosensors on spinach leaf surfaces was demonstrated. This multilayer scanning coil detector therefore facilitates the detection of pathogens on food and food contact surfaces.
Rapid and Sensitive Detection of Salmonella Typhimurium on Plastic Food Processing Plates By Using Wireless Biosensors
Authors: Liu Yuzhe , Horikawa Shin , Du Songtao , Chai Yating , Hu Jiajia , Wang Fengen , Chin Bryan A
Published: February 2020

Food products can be contaminated with bacteria, spores, viruses, toxins and other pathogens at any point in the farm-to-table continuum. This paper presents an investigation into rapid, sensitive detection of Salmonella Typhimurium on plastic food processing plates by using wireless magnetoelastic (ME) biosensors. In this research, a planar spiral coil was microfabricated and employed as a surface-scanning detector for real-time, in-situ measurement of the biosensors without sample preparation and/or enrichment in the testing process. The ME biosensor consists of an ME resonator, made from metallic glass (Metglas alloy 2826MB), as the signal transducer and E2 phage as the bio-molecular recognition element that is engineered to selectively bind with Salmonella Typhimurium. The ME biosensor is a type of mass-sensitive biosensors that can be wirelessly actuated into mechanical resonance by an externally applied time-varying magnetic field. Both measurement sensors (multiple E2 phage-coated biosensors) and control sensors (multiple biosensors without phage) were prepared and distributed on a food grade PET plate contaminated with S. Typhimurium with known volumes and concentrations. The resonant frequency changes of the measurement sensors due to specific binding of S. Typhimurium were found to be statistically different from those of the control sensors. The effects of sensor distribution and the surface roughness of PET plates (in the range of 0.25 to 1 um) on ME biosensor detection were also investigated.
ZnO Nanostructures with Different Morphologies and Their Combinatorial Optimization with Graphene Oxide for Gas Sensor Properties
Authors: Lee Eunji
Published: February 2020

Consumer concerns on food safety and quality are increasing worldwide. Without opening the package of food products, collecting information about freshness of the product is desirable. Therefore, an electronic nose device consisting of multiple gas sensors can be utilized for rapid monitoring of food quality and freshness at low cost. Such multiple gas sensors, i.e array structure can provide selective detection and identification of various compounds by linking gas responses to signal process. Gas sensors based on chemical reaction on the surface of semiconducting metal oxides are readily available commercially. Common material of the metal oxide sensor is tin oxide doped with a small amount of a catalytic metal such as palladium or platinum. The improvement of gas sensing performance such as low operating temperature as well as selective and sensitive detection can be obtained by investigating potential oxides with controlled morphologies at the nanoscale and their composite structures.

Among various semiconducting materials, ZnO is an excellent candidate for gas sensor applications. In addition, many methods can be utilized to fabricate various ZnO nanostructures. Solution process can be simple and effective bottom-up path to construct hierarchical ZnO nanostructures on various substrates. Therefore, we investigated a solution method as controlling the morphology of ZnO nanostructures by applying DC and AC bias and by selecting different precursors. ZnO nanorods structure was synthesized using zinc nitrate hexahydrate and HMT (hexamethylenetetramine) in aqueous solution. The use of zinc chloride instead of zinc nitrate hexahydrate for zinc precursor, nanoflake structure was successfully fabricated where zinc chloride serves as a capping ion to prevent isotropic growth. With applying external voltage during solution growth, ZnO nanorods became agglomerate structures and the degree of agglomerates varies depending on the range of external bias.

Various ZnO nanostructures have been analyzed with SEM, XRD and UV-visible. Figure 1 shows one example of morphological control of ZnO nanostructures according to applying bias and precursors. The change of morphologies showed different degree of orientation of the structures by XRD result. Gas sensing response was measured to extract characteristic feature at different ZnO morphologies. Elevated operating temperature approaching 200 – 300°C from ZnO gas sensor can be lowered by combining graphene oxide (GO). Various combinatorial structures from ZnO and GO were explored. Detailed discussion on gas sensing properties and their mechanisms will be given.

Figure 1
Functionality Supports Synthesis of Tungsten Carbides for Catalytic Applications By Arc Plasma Deposition Process
Authors: Oh JI-Won , Na Hyunwoong , Kim Kyou-Hyun , Son Seong Ho , Nahm Sahn , Choi Hanshin
Published: February 2020

Tungsten carbides(WC) are applied for both catalysts and supports for other catalysts. Tungsten(W) is directly deposited on carbon black particle via physical vapor deposition process and then thermo-chemical conversion reaction. It is also difficult to distribute constituent nanoparticles uniformly. To overcome the dispersion uniformity, tungsten(W) is directly deposited on carbon black support via physical vapor deposition. Pure tungsten(W) or tungsten oxide(WO3) is converted into tungsten carbide(WC) via interaction with carbonaceous materials. On the other hand, It was occurred for in-situ carburization to Arc Plasma Deposition(APD) process using tungsten(W) target. and crystallinity of carbon black(Vulcan VX-72) support was Enhanced. Tungsten carbides(WC) nano-attached particle can be used for final products or precursors for end products.