Photodeposition of platinum nanoparticles on wel-defined tungsten oxide : controlling oxidation state, particle size and geometrical distribution

Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions.

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ZnWO4 Nanoparticle Scintillators for High Resolution X-ray Imaging

Nanomaterials ◽

10.3390/nano10091721 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1721

Author(s):

Heon Yong Jeong ◽

Hyung San Lim ◽

Ju Hyuk Lee ◽

Jun Heo ◽

Hyun Nam Kim ◽

...

Keyword(s):

Particle Size ◽

Zinc Oxide ◽

High Resolution ◽

Tungsten Oxide ◽

Spatial Resolution ◽

High Spatial Resolution ◽

X Ray ◽

X Ray Imaging ◽

Average Size ◽

And Tungsten

The effect of scintillator particle size on high-resolution X-ray imaging was studied using zinc tungstate (ZnWO4) particles. The ZnWO4 particles were fabricated through a solid-state reaction between zinc oxide and tungsten oxide at various temperatures, producing particles with average sizes of 176.4 nm, 626.7 nm, and 2.127 μm; the zinc oxide and tungsten oxide were created using anodization. The spatial resolutions of high-resolution X-ray images, obtained from utilizing the fabricated particles, were determined: particles with the average size of 176.4 nm produced the highest spatial resolution. The results demonstrate that high spatial resolution can be obtained from ZnWO4 nanoparticle scintillators that minimize optical diffusion by having a particle size that is smaller than the emission wavelength.

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Review on the Synthesis Methods of Nano-Tungsten Oxide Dihydrate Colloid

MATEC Web of Conferences ◽

10.1051/matecconf/202133503008 ◽

2021 ◽

Vol 335 ◽

pp. 03008

Author(s):

Khizar Mushtaq ◽

Pui May Chou ◽

Chin Wei Lai

Keyword(s):

Particle Size ◽

Tungsten Oxide ◽

Sol Gel ◽

Synthesis Method ◽

Transition Element ◽

Cost Effective ◽

Processing Parameters ◽

Synthesis Methods ◽

Cost Effective Method ◽

Future Work

Tungsten being a transition element, forms oxide compounds of various oxidation states that enables it to form nanocolloids of tungsten oxide dihydrate. Multiple methods have been used in recent years to synthesize nano tungsten oxide dihydrate, including sol-gel synthesis, electrochemical deposition, hydrothermal synthesis and anodization. However, a universally accepted synthesis method for this material is not offered. The most appropriate method and its corresponding processing parameters for the synthesis of nano tungsten oxide dihydrate colloids were presented in the present study. The objective of the present study was to investigate the effect of processing parameters, i.e. applied voltage, temperature and anodizing duration on the particle size of nanocolloids. It is found that anodization is the easiest, efficient, and cost-effective method to synthesize the colloidal solution of nano tungsten oxide dihydrate. Conducting the synthesis at room temperature at a voltage of 50 V for 60 minutes yields the product with particle size of 40 – 60 nm, which can be used in wide array of applications. This paper also highlights the research gaps for future work and gives recommendations to extend this study particularly for the industrial application of tungsten oxide.

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Quasi Similar Routes of NO2 and NO Sensing by Nanocrystalline WO3: Evidence by In Situ DRIFT Spectroscopy

Sensors ◽

10.3390/s19153405 ◽

2019 ◽

Vol 19 (15) ◽

pp. 3405 ◽

Cited By ~ 11

Author(s):

Lili Yang ◽

Artem Marikutsa ◽

Marina Rumyantseva ◽

Elizaveta Konstantinova ◽

Nikolay Khmelevsky ◽

...

Keyword(s):

Particle Size ◽

Nitrogen Oxides ◽

Tungsten Oxide ◽

High Sensitivity ◽

Tungstic Acid ◽

Drift Spectroscopy ◽

Reaction Conditions ◽

Sensing Applications ◽

Sensor Signals

Tungsten oxide is a renowned material for resistive type gas sensors with high sensitivity to nitrogen oxides. Most studies have been focused on sensing applications of WO3 for the detection of NO2 and a sensing mechanism has been established. However, less is known about NO sensing routes. There is disagreement on whether NO is detected as an oxidizing or reducing gas, due to the ambivalent redox behavior of nitric oxide. In this work, nanocrystalline WO3 with different particle size was synthesized by aqueous deposition of tungstic acid and heat treatment. A high sensitivity to NO2 and NO and low cross-sensitivities to interfering gases were established by DC-resistance measurements of WO3 sensors. Both nitrogen oxides were detected as the oxidizing gases. Sensor signals increased with the decrease of WO3 particle size and had similar dependence on temperature and humidity. By means of in situ infrared (DRIFT) spectroscopy similar interaction routes of NO2 and NO with the surface of tungsten oxide were unveiled. Analysis of the effect of reaction conditions on sensor signals and infrared spectra led to the conclusion that the interaction of WO3 surface with NO was independent of gas-phase oxidation to NO2.

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Sub 3 nm particle size and composition dependent response of a nano-CPC battery

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-8855-2013 ◽

2013 ◽

Vol 6 (5) ◽

pp. 8855-8887

Author(s):

J. Kangasluoma ◽

C. Kuang ◽

D. Wimmer ◽

M. P. Rissanen ◽

K. Lehtipalo ◽

...

Keyword(s):

Particle Size ◽

Sodium Chloride ◽

Tungsten Oxide ◽

Ammonium Sulphate ◽

Detection Efficiency ◽

The Other ◽

Oxidation Products ◽

Working Fluid ◽

Ammonium Bromide ◽

Activation Efficiency

Abstract. In this study we built a nano-CPC battery, consisting of four ultrafine CPCs optimized for the detection of sub 3 nm particles. Two of the CPCs use diethylene glycol as a working fluid: a laminar type diethlylene glycol CPC and a mixing type Airmodus A09 Particle Size Magnifier. The other two CPCs are a laminar type TSI 3025A and a TSI 3786 with butanol and water as the working fluids, respectively. The nano-CPC battery was calibrated with seven different test aerosols: tetra heptyl ammonium bromide, ammonium sulphate, sodium chloride, tungsten oxide, sucrose, candle flame products and limonene ozonolysis products. The results show that ammonium sulphate and sodium chloride have a higher activation efficiency with the water-based 3786 than with the butanol-based 3025A, whereas the other aerosols were activated better with butanol than with water as the working fluid. It is worthwhile to mention that limonene ozonolysis products were detected very poorly with all of the CPCs, butanol being the best fluid to activate the oxidation products. To explore how the detection efficiency is affected if the aerosol is an internal mixture of two different chemical substances, we made the first attempt to control the mixing state of sub 3 nm laboratory generated aerosol. We show that we generated an internally mixed aerosol of ammonium sulphate nucleated onto tungsten oxide seed particles, and observed that the activation efficiency of the internally mixed clusters was a function of the internal mixture composition.

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Ultrafine Tungsten Powder Obtained with Violet Tungsten Oxide Using Circulatory Oxidization-Reduction Method

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.127.101 ◽

2011 ◽

Vol 127 ◽

pp. 101-104

Author(s):

Xiao Ming Fu

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Tungsten Oxide ◽

Size Distribution ◽

Reduction Method ◽

Tungsten Powder ◽

Hydrogen Gas ◽

Dew Point ◽

Measuring Instrument ◽

Argon Gas

Violet tungsten oxide is prepared with pure ammonium paratungstate in the argon gas. Tungsten powder is obtained with violet tungsten oxide through deoxidation in the hydrogen gas (Rate of purity: 99.99 %, dew point: -40 °C), and tungsten powder is oxidized in the air. Tungsten oxide is reduced with tungsten powder in the hydrogen gas. The samples are characterized with the laser particle size distribution measuring instrument and field-emission scanning electron microscope. The results show that ultrafine tungsten powder is obtained through circulatory oxidation twice and reduction three times. The percentage of the particle size distribution of ultrafine tungsten powder is 95.73 % between 0.1 μm and 1.0 μm.

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Citrate-Coated Platinum Nanoparticles Exhibit a Primary Particle-Size Dependent Effect on Stimulating Melanogenesis in Human Melanocytes

Cosmetics ◽

10.3390/cosmetics7040088 ◽

2020 ◽

Vol 7 (4) ◽

pp. 88

Author(s):

Shilpi Goenka ◽

Jimmy Toussaint

Keyword(s):

Particle Size ◽

Platinum Nanoparticles ◽

Primary Particle ◽

Primary Particle Size ◽

Hair Follicles ◽

Catechol Oxidase ◽

Personal Care ◽

Free System ◽

White Skin ◽

Human Melanocytes

Hypopigmentation disorders due to an underproduction of the pigment melanin by melanocytes cause uneven skin coloration, while in hair follicles they cause grey hair. There is a need for novel materials which can stimulate melanogenesis in the skin and hair for personal care use. While titanium dioxide, gold and silver nanoparticles have been extensively used for applications in cosmetic and personal-care products (PCP), the use of relatively inert platinum nanoparticles (PtNPs) has remained underappreciated. PtNPs have been reported to be a mimetic of the enzyme catechol oxidase with small size PtNPs reported to exhibit a higher catechol oxidase activity in a cell-free system, but no testing has been conducted in melanocytes to date. Herein, we have investigated if PtNPs of two sizes (SPtNP: 5 nm; LPtNP: 50 nm) might have an effect on melanogenesis. To this end, we have used MNT-1 human melanoma cells and primary human melanocytes from moderately-pigmented skin (HEMn-MP). Both SPtNP and LPtNP were nontoxic over a concentration range 6.25–25 μg/mL, hence these concentrations were used in further experiments. Both PtNPs stimulated higher extracellular melanin levels than control; SPtNP at concentrations 12.5 and 25 μg/mL significantly stimulated higher levels of extracellular melanin as compared to similar concentrations of LPtNP in MNT-1 cells, in the absence of ROS generation. The effects of PtNPs on melanin secretion were reversible upon removal of PtNPs from the culture medium. The results of primary particle size-specific augmentation of extracellular melanin by SPtNPs were also validated in HEMn-MP cells. Our results thus provide a proof-of-principle that SPtNP might hold potential as a candidate for the treatment of white skin patches, for sunless skin-tanning and for use in anti-greying hair products in cosmetics.

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