An illustrated diagram labels KATRIN's main components
electron-counting machine has indirectly turned up a measurement of the slipperiest known particle in physics — and added to the evidence for dark matter
That measurement is the first result from an international effort to measure the mass of neutrinos — particles that fill our universe and determine its structure
but which we're barely able to detect at all
according to the German-based Karlsruhe Tritium Neutrino experiment (KATRIN)
have no more than 0.0002% the mass of an electron
That number is so low that even if we tallied up all of the neutrinos in the universe
they couldn’t explain its missing mass
And that fact adds to the pile of evidence for dark matter's existence
a KATRIN scientist and professor emeritus at the University of Washington
because it's the only electron-neutrino source simple enough to get a good mass measurement from
Neutrinos are more or less impossible to precisely measure on their own because they have so little mass and tend to skip out of detectors without interacting with them
So to figure out the mass of the neutrinos
KATRIN counts the most energetic electrons and works backward from that number to deduce the neutrino's mass
The first results from KATRIN have been announced
and the researchers came to an early conclusion: Neutrinos have a mass no higher than 1.1 electron volts (eV).
Electron volts are the units of mass and energy physicists use when talking about the smallest things in the universe. (At the scale of fundamental particle, energy and mass are measured using the same units
and the neutrino-electron pairs have to have combined energy levels equivalent to their source neutron.) The Higgs boson
This experiment confirms that neutrinos are incredibly tiny.
Related: 9 Ideas About Black Holes That Will Blow Your Mind
The device's first chamber is full of gaseous tritium, whose neutrons naturally decay into electrons and neutrinos
Physicists already know how much energy is involved when a neutron decays
Some of the energy is converted into the mass of the neutrino and the mass of the electron
And the rest gets poured into those newly-created particles
that extra energy gets distributed pretty evenly between the electron and the neutrino
But sometimes most or all of the remaining energy gets dumped into one particle or another.
Get the world’s most fascinating discoveries delivered straight to your inbox
all of the energy left over after the neutrino and electron are formed is dumped into the electron partner
That means the mass of the neutrino can be calculated: It’s the energy involved in the neutron decay minus the mass of the electron and the maximum energy level of electrons in the experiment
The physicists who designed the experiment didn't try to measure the neutrinos; those are allowed to escape the machine untouched
the experiment funnels the electrons into a giant vacuum chamber
An electric current then creates a very strong magnetic field that only the highest-energy electrons can pass through
At the other end of that chamber is a device that counts how many electrons make it through the field
As KATRIN slowly increases the magnetic field strength
the number of electrons getting through shrinks — almost as if it were going to fade all the way to zero
But at the very end of that spectrum of electron energy levels
before you reach the end point [where the electron would have all the energy released in the tritium decay]
because the mass of the neutrino can't be stolen by the electron
It always has to be left behind for the neutrinos," Robertson said
The mass of the neutrino must be less than that tiny amount of energy missing from the very end of the spectrum
the experimenters narrowed that number down to about half of the number that physicists previously knew about
The idea that neutrinos have mass at all is revolutionary; the Standard Model, the mainstay physics theory that describes the subatomic world, once insisted neutrinos have no mass at all
Russian and American researchers were trying to measure neutrino masses
but their results were problematic and imprecise
Russian researchers pegged the mass of the neutrino at precisely 30 eV — a nice number that would have revealed neutrinos as the missing link that would have explained the grand gravitational structure of the universe
filling in all the missing mass — but one that turned out to be wrong
Robertson and his colleagues first started working with gaseous tritium back then
after they realized that the faintly radioactive substance offered the most precise source of neutron decay available to science
"This has been a long search," Robertson said
"The [incorrect] Russian measurement of 30 eV was very exciting because it would have closed the universe gravitationally
and they have probably shaped the large scale structure of the universe."
All of those faint particles flying around tug on everything else with their gravity
and take and lend energy from all the other matter
Though as the mass number gets whittled down
the precise role these little particles play gets more complicated
is interesting because it's the first experimentally-derived neutrino mass number that isn't high enough to explain the structure of the rest of the universe on its own
"There is matter that is not anything we know about yet. There is this dark matter,” and it can’t be made of of the neutrinos that we know about
So this small number from a big vacuum chamber in Germany at the very least adds to the pile of evidence that the universe has elements that physics still doesn't understand
Originally published on Live Science
Gamma-ray bursts reveal largest structure in the universe is bigger and closer to Earth than we knew: 'The jury is still out on what it all means.'
Universe may revolve once every 500 billion years — and that could solve a problem that threatened to break cosmology
Amateur astronomer captures detailed photos of Croc's Eye and Whirlpool galaxies from backyard observatory
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Polyoxometalates (POM) are anionic oxoclusters of early transition metals that are of great interest for a variety of applications
including the development of sensors and catalysts
A crucial step in the use of POM in functional materials is the production of composites that can be further processed into complex materials
we present an immobilization approach for POMs that involves two key processes: first
the stable encapsulation of POMs in the pores of mesoporous silica nanoparticles (MSPs) and
the formation of microstructured arrays with these POM-loaded nanoparticles
we have developed a strategy that leads to water-stable
POM-loaded mesoporous silica that can be covalently linked to alkene-bearing surfaces by amine-Michael addition and patterned into microarrays by scanning probe lithography (SPL)
The immobilization strategy presented facilitates the printing of hybrid POM-loaded nanomaterials onto different surfaces and provides a versatile method for the fabrication of POM-based composites
POM-loaded MSPs are useful in applications such as microfluidic systems and sensors that require frequent washing
this method is a promising way to produce surface-printed POM arrays that can be used for a wide range of applications
with the direct use of Gd enhancing the NMR signal instead of nitrogen-vacancy (NV) centers acting as a proxy for readout
MSPs are loaded with POMs to create POM-loaded MSPs
These are then spotted via scanning probe lithography (SPL) methods into microarrays on alkene-bearing surfaces
The POM-loaded MSPs are then immobilized on the surface by amine-Michael addition
which is in good agreement with previously published results
which revealed a nearly neutral surface charge (0.4 ± 1.2) mV of MSPs+
This reduced negative Z-pot value (for non-functionalized and surfactant-extracted MSP
the Z-pot is around − 30 to − 40 mV) can be explained by the surface passivation that took place
which reduces the amount of deprotonated and negatively charged hydroxyl groups on the surface of the particles
as well as by charge balancing due to the positive R-NH3+ groups present on the pore entrances
(C) Left: representative SEM image of MSPs-POM and the region (white rectangle) subjected to EDX analysis
Right: atomic weight fractions and errors from EDX analysis of MSPs-POM
(A) Number intensity weighted DLS size distribution of MSPs-POM in PBS buffer (10X
pH 7.5 at 37 °C) and (B) corresponding autocorrelation functions (ACF) over 5 days
(A) Schematic illustration of MPS-modified surfaces functionalization by thiol-ene and amine-ene click reactions and chemical structure of probes used to test the surface reactivity
Results of the characterization of MPS-modified surfaces by (B) WCA
and (D) XP spectra at C 1s region of bare glass and MPS-modified surfaces
The deconvoluted HR-XP spectra exhibit three peaks a 284.8 eV
Comparing the XP spectra of the bare glass and MPS-modified samples
which indicates the formation of the MPS-modified SAM
Fluorescent images of microarrays for (A) NH2-Tamra (exposure time 300 ms) and (B) SH-FITC (exposure time 1 s) spots after finished click-reactions and washing of MPS-modified surfaces
Fluorescent images of (C) NH2-Biotin and (D) SH-Biotin spotted MPS-modified surfaces after incubation of SA-Cy3 (Exposure time 500 ms)
(E) Fluorescence intensity of SA-Cy3 coupled patterns collected from images in C and D
The yield of the thiol-ene click route (9620.86 ± 1148.15) a.u
is about 21% higher than amine-ene route (7585.39 ± 1046.44) a.u
though both routes appear similar within the fluctuations
both routes deliver a comparable and stable binding to the surface
(A) Bright field and (B) fluorescence microscopy image of capillary printed microarrays of MSPs-POM ink
(C) Fluorescence microscopy image of the microarray after washing
and fluorescence microscopy images (E) before and (F) after the heating and washing step
(G) SEM image of two immobilized MSPs-POM particles
(H) AFM image of an immobilized MSPs-POM particle
further confirming the successful binding to the surface and integrity of the modified MSPs-POM
complex functional constructs can be fabricated
we think that this MSPs-POM offers an attractive for the immobilization of functional POMs into surface-bound patterns for future applications in biomedical sensing and catalysis
All solvents for synthesis were purchased from VWR and used as received
Water (18.2 MΩ∙cm) was collected from an Arium (Sartorius) laboratory-grade water purification system
Gadolinium(III) nitrate hexahydrate (Gd(NO3)3·6H2O)
sodium tungstate (Na2WO4) and potassium chloride (KCl) were purchased from VWR
2-methoxy(polyethyleneoxy)propyltrimethoxysilane (90%
6–9 PEG units) was purchased from ABCR Chemie
Sulfo-cyanine3 (Cy3) NHS ester (95%) was purchased from Lumiprobe
and glycerol were purchased from Sigma-Aldrich (Germany)
5-isomer (NH2-Tamra) was bought from Lumiprobe GmbH (Germany)
MW 2000 (SH-Biotin) and Fluorescein-PEG-Thiol (SH-FITC) were obtained from Nanocs Company (USA)
3-methacryloxypropyltrimethoxysilane (MPS-silane)
and phosphate-buffered saline (PBS) were obtained from Sigma-Aldrich (Germany)
Pristine MSPs were prepared according to a previously described procedure51
0.27 mmol) in an H2O/EtOH mixture (60/30 v/v
The resulting reaction mixture was stirred for 16 h at room temperature
1/3 of the particle dispersion was taken and used for further functionalization steps
2-methoxy(polyethyleneoxy)propyltrimethoxysilane (183.0 µL; 0.38 mmol) was added and the reaction mixture was stirred for 4 h at 60 °C
the particles were recovered by centrifugation (20 min
2x) by cycle sonication and subsequent centrifugation
The surfactant was removed from the pores of the MSPs by extraction in EtOH
the particles were dispersed in EtOH (50 mL)
diluted HCl (50 µL; 250 µL HCl diluted in 2 mL EtOH) was added
The particles were collected by centrifugation and washed by sonication and centrifugation in EtOH (50 mL
The collected precipitate was refluxed again in EtOH as described above
the particles were washed with EtOH (50 mL
To functionalize the surfactant-free pore walls of the particles
the surfactant-extracted MSP were dispersed in EtOH (10 mL) and (3-aminopropyl)trimethoxysilane (66.0 µL
The resulting reaction mixture was stirred at room temperature for 12 h
The particles were then collected by centrifugation and washed by sonication and centrifugation with EtOH (20 mL
To determine the optimal loading process in which no POM crystals are visible on the surface of the particles or next to the nanoparticles
we developed an optimized loading and washing process
To a dispersion of MSPs+ (10 mg) in water (1 mL) POM (40 mg) was added and the resulting mixture was briefly sonicated and stirred at room temperature for 12h
The particles were then collected by centrifugation and subsequently washed with EtOH (1×) and finally with H2O (5×)
In a glass vial (2 mL) with a magnetic stirrer
MSPs-POM was dispersed in 10X PBS buffer (pH = 7.5) by brief sonication (cparticles = 0.01 mg·mL−1)
The resulting particle dispersion was sealed and stirred at 37 °C for 5 days
aliquots were taken and used to measure the DLS and Z-potential of the sample
The measurements were performed using a Malvern ZetaSizer Nano instrument. The intensity of the scattered light was measured at a fixed angle (173°). The wavelength of the laser light used for the light scattering experiments was 633 nm. Data analysis was performed according to standard procedures using the Malvern software (v3.30, https://www.malvernpanalytical.com/)
the decay rates were determined by the following relationship
The method of cumulants was used to fit the autocorrelation function
which in turn allows the determination of the diffusion coefficient (d)
from which the hydrodynamic diameter (Dh) of the aggregates is calculated using the Stokes–Einstein equation (see below)
The measurements were performed using the Malvern ZetaSizer Nano instrument
A viscosity of μ = 0.8984 cP and a dielectric constant of ε = 79 and a refractive index of 1.33304 were used
Analysis of data was performed utilizing Zetasizer Software 6.12 (Malvern Instruments GmbH
Germany) based on the model of Smoluchowski
the Sulfo-Cy3 alkoxysilane used for fluorescent labeling of the particles is prepared
from a 100 µM stock solution in dry DMSO) is added to a solution of Sulfo-Cy3-NHS ester (0.6 mg
0.8 µmol) in dry DMSO (50 µL) in a glass vial
and allowed to react for 30 min at room temperature
A dispersion of the MSPs-POM (10 mg) in toluene (500 µL) was also prepared
the crude SulfoCy3-silane mixture and APTMS (10 µL) were added
and the reaction mixture was stirred for 12 h at 60 °C
The particles were then collected by centrifugation and washed with EtOH until no sulfo-Cy3 was detected in the supernatant of the wash solutions
The particles were then dried under reduced pressure
FT-IR spectroscopy was employed to analyze the acquired compounds using the ATR module of a NicoletTM iS50 spectrometer
and the resulting data was visualized using Origin 2018b
Germany) were cleaned by sonication in chloroform
and water for 5 min each and then dried with nitrogen
the freshly hydroxylated substrates were immersed in a freshly prepared MPS-silane solution in toluene (1%
and then the substrates were washed with toluene
the MPS-modified glass samples were stored in a desiccator
Ink solutions for click reaction were prepared by mixing thiol-containing or amine-containing compounds in a mixture of DMSO/TEA (10:3
To avoid fast evaporation of the ink solvent
an amount of 30% (v/v) of glycerol was added to the ink solutions
The final concentration of the ink solutions was 2 mg/mL
but without connection of a microfluidic pump
the capillary tips were simply immersed in a reservoir of the MSPs-POM solution
enabling the loading of ink via capillary forces
Microarrays with MSPs-POM (5 × 5 spot array with 300 µm pitch) were obtained with a glass capillary tip of approx
100 µm aperture in an NLP 2000 system (Nanoink
USA) under 40% relative humidity with a dwell time for each spot of 1s
The samples were then incubated at 37°C for 3 h and left at RT overnight to complete the click reaction
excess ink was removed by washing with water
The energy scale of the spectra was set to 285 eV based on the C–C/C–H part of the C1s signal
A Shirley background was used for the evaluation of the high-resolution spectra
The optical images were captured on a Nikon Eclipse 80i upright fluorescence microscope (Nikon
Germany) equipped with an Intensilight illumination (Nikon
The microscope collected the fluorescence intensity data with the built-in NIS-element software (Nikon
The SEM images were acquired with a Zeiss Ultra-Plus SEM at 3 kV and
The EDX measurements were performed with a Zeiss Leo 1530 SEM operating at 20 kV
The EDX data were acquired with Oxford Instruments AZtec software using an Oxford X-MaxN 50 detector
All data shown in this work were described as means ± standard deviations
The values of fluorescence intensity were obtained by an on-board software (NIS Elements AR 5.02.01
The original data of WCA and roughness were obtained by measuring 3 random points of each sample
and the means and standard deviations were computed on excel by STDEVA formula
The datasets used and/or analysed during the current study available from the corresponding author on reasonable request
Polyoxometalates: Building blocks for functional nanoscale systems
Polyoxometalate chemistry: An old field with new dimensions in several disciplines
Borrás-Almenar, J. J. et al. (eds) Polyoxometalate Molecular Science (Springer, Netherlands, 2003). https://doi.org/10.1007/978-94-010-0091-8
Hybrid polyoxometalates as post-functionalization platforms: from fundamentals to emerging applications
Polyoxometalates as potential next-generation metallodrugs in the combat against cancer
Gd 3 triangles in a polyoxometalate matrix: Tuning molecular magnetocaloric effects in Gd 30 M 8 polyoxometalate/cluster hybrids through variation of M 2+
Polyoxometalates as chemically and structurally versatile components in self-assembled materials
Hierarchical organization of perylene bisimides and polyoxometalates for photo-assisted water oxidation
Photoreduction of carbon dioxide to carbon monoxide with hydrogen catalyzed by a rhenium(I) phenanthroline−polyoxometalate hybrid complex
A heteropolyanion with fivefold molecular symmetry that contains a nonlabile encapsulated sodium ion
The structure and chemistry of [NaP5W30O110]14-
Rigid nonlabile polyoxometalate cryptates [ZP5W30O110](15-n)- that exhibit unprecedented selectivity for certain lanthanide and other multivalent cations
Diamond - Crystal and Molecular Structure Visualization, Crystal Impact - Dr. H. Putz & Dr. K. Brandenburg GbR, Kreuzherrenstr. 102, 53227 Bonn, Germany. https://www.crystalimpact.de/diamond
Recent advances of polyoxometalates in multi-functional imaging and photothermal therapy
Polyoxometalate-based nanomaterials toward efficient cancer diagnosis and therapy
Quantum sensors for biomedical applications
Engineering Gd-loaded nanoparticles to enhance MRI sensitivity via T1 shortening
Polyoxometalate-based high-spin cluster systems: A NMR relaxivity study up to 1.4 GHz/33 T
Polyoxometalate-soft matter composite materials: Design strategies
Immobilization of polyoxometalates in crystalline solids for highly efficient heterogeneous catalysis
Polyoxometalate-functionalized nanocarbon materials for energy conversion
structures and applications of electron-rich polyoxometalates
Polyoxometalate functionalized sensors: A review
Silica nanoparticles—A versatile tool for the treatment of bacterial infections
Europium polyoxometalates encapsulated in silica nanoparticles – Characterization and photoluminescence studies
Lanthanopolyoxometalate-silica core/shell nanoparticles as potential MRI contrast agents
Nuclear magnetic resonance detection and spectroscopy of single proteins using quantum logic
Surface NMR using quantum sensors in diamond
The synthesis of micrometer- and submicrometer-size spheres of ordered mesoporous oxide MCM-41
Synthesis of mesoporous silica nanoparticles
On the controllable soft-templating approach to mesoporous silicates
Facile large-scale synthesis of monodisperse mesoporous silica nanospheres with tunable pore structure
Synthesis of nanoscale mesoporous silica spheres with controlled particle size
Morphology control of mesoporous silica particles using bile acids as cosurfactants
Mesoporous silica nanoparticle nanocarriers: Biofunctionality and biocompatibility
Molecular engineering of surface functional groups enabling clinical translation of nanoparticle-drug conjugates
Mesoporous silica nanoparticles for drug delivery
A selective functionalized mesoporous silica-supported Rh catalyst for effective 1-octene hydroformylation
Accessibility of amino groups in postsynthetically modified mesoporous silica
Mesoporous silica nanoparticles functionalized with amino groups for biomedical applications
Functionalized large pore mesoporous silica nanoparticles for gene delivery featuring controlled release and co-delivery
Highly active enzymes immobilized in large pore colloidal mesoporous silica nanoparticles
Chemically directed immobilization of nanoparticles onto gold substrates for orthogonal assembly using dithiocarbamate bond formation
Asymmetric printing of molecules and zeolites on self assembled monolayers
Efficiency of polyoxometalate-based mesoporous hybrids as covalently anchored catalysts
Covalent immobilization of a TiW5 polyoxometalate on derivatized silicon surfaces
Covalent attachment of polyoxometalates to passivated Si(111) substrates: A stable and electronic defect-free Si|POM Platform
Highly degradable imine-doped mesoporous silica particles
Organosilica cages target hepatic sinusoidal endothelial cells avoiding macrophage filtering
Enhanced thermal stability and lifetime of epoxy nanocomposites using covalently functionalized clay: experimental and modelling
Spectroscopic investigation of the mechanisms responsible for the superior stability of hybrid class 1/Class 2 CO2 sorbents: A new class 4 category
Molecular conformation in oligo(ethylene glycol)-terminated self-assembled monolayers on gold and silver surfaces determines their ability to resist protein adsorption
Bio-degradation study of colloidal mesoporous silica nanoparticles: Effect of surface functionalization with organo-silanes and poly(ethylene glycol)
Stability of small mesoporous silicananoparticles in biological media
Surface molecular imprinting for chemiluminescence detection of the organophosphate pesticide chlorpyrifos
AgVO3 nanorods silanized with γ-MPS: An alternative for effective dispersion of AgVO3 in dental acrylic resins improving the mechanical properties
Evaluation of dibenzocyclooctyne and bicyclononyne click reaction on azido-functionalized antifouling polymer brushes via microspotting
Solvent-dependent adhesion strength of electroless deposited Ni–P layer on an amino-terminated silane compound-modified Si wafer
Streptavidin-biotin technology: Improvements and innovations in chemical and biological applications
A comparative study of thiol-terminated surface modification by click reactions: Thiol-yne coupling versus thiol-ene michael addition
Protein microarray immobilization via epoxide ring-opening by thiol
Development of dip-pen nanolithography (DPN) and its derivatives
High-resolution capillary printing of eutectic gallium alloys for printed electronics
Systematic and collaborative approach to problem solving using X-ray photoelectron spectroscopy
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Open Access funding enabled and organized by Projekt DEAL
Institute of Biological and Chemical Systems – Functional Molecular Systems (IBCS-FMS)
College of Materials Science and Engineering
Institute for Quantum Materials and Technologies (IQMT)
K.B.; Synthesis and characterization of MSPs-POM: P.P.
C.S.; Electron microscopy and analysis: S.M.; XPS measurements: D.M.
M.H.; All authors were involved in revising the manuscript
The authors declare no competing interests
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations
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DOI: https://doi.org/10.1038/s41598-023-50846-2
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Reliable environmental monitoring requires cost effective but highly sensitive and selective gas sensors
While the sensitivity of the sensors is improved by reducing the characteristic dimensions of the gas-sensing material
the selectivity is often approached by combining the sensors into multisensor arrays
The development of scalable methods to manufacture such arrays based on low-dimensional structures offers new perspectives for gas sensing applications
Here we examine an approach to produce multisensor array chips based on the TiOx nanotube layers segmented by multiple Pt strip electrodes
We study the sensitivity and selectivity of the developed chip at operating temperatures up to 400 °C towards organic vapors in the ppm range
The results indicate that the titania nanotubes are a promising material platform for novel cost-effective and powerful gas-analytical multisensor units
into arrays and process the obtained vector signal by pattern recognition techniques
we demonstrate the capability of the chip to selectively detect few exemplary organic vapors at ppm concentrations
The scheme of fabrication the multisensor chip based on TiOx NT array: (a–e) denote respectively Ti foil (a)
the scheme of multisensor chip wired into 50-pin ceramic card (e)
The Si/SiO2 chip substrate equipped with multiple Pt strip electrodes provides a number (up to 38) of NT array segments whose electrical/chemiresistive properties are measured independently
Following the transfer into the chip the TiOx NT array possesses a structural integrity as evidenced by scanning electron microscopy (SEM) inspection (Fig. 2a); the NTs are characterized with a distinct morphology (Fig. 2b).
Characterization of the TiOx NT arrays used in the multisensor chip: (a) SEM image taken of the chip surface covered with NT array; (b) HAADF-STEM image
the inset shows a surface rendering of the 3D STEM tomographic reconstruction viewed along the NT length; (c,d) SAED patterns of as-grown NTs and NTs annealed at 400 °C
respectively; (e,f) the XPS peaks related to Ti 2p (e) and O 1s (f) for the as-grown NTs
red lines show the envelope curves of all fitted peaks to compare with the experimental data (open circles)
In order to clarify the structure and morphology of NTs we have extracted the NT array out of the same batch as the ones employed in the chip for additional characterization by high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS) techniques; the details are given in Methods
The anatase crystal structure of annealed NTs is manifested by lattice strong reflections of (101)
(105) planes corresponding to d-values of 3.52 Å
1.75 Å and reflections from other crystal planes (see Supplementary)
Such minor variations of structure and elemental composition in NTs have been out of XPS detection in our samples but still could contribute to the observed differences in local electrical and gas-sensitive properties along NT array membrane as further discussed
The electrical characterization of TiOx NT array based multisensor chip: (a) I–V curves recorded from three exemplary segments under constant flow (100 sccm) of laboratory air at 350 °C; (b) the dependence of chip segments response to 10 ppm of ethanol
and acetone on operating temperature; (c) the dependence of chip segments response on vapor (ethanol
and acetone) concentration in air at 350 °C; (d) the variations of the chip segments resistances
to pulses of isopropanol at different ppm concentrations under operating temperature of 350 °C; thick black line denotes the segments median resistance
The similar data have been observed in case of other test vapors at different temperatures
A schematic representation to show the change in the conductivity and conduction pathway for electrons through TiOx NT array at two environments - air and mixture of air and reducing agents: (a) the modification of potential barrier heights following the adsorption of the species of different origin and their surface reactions; (b) SEM images of the NT array from top and side views corresponding to the presented scheme
This explains the higher response of the NTs towards isopropanol and acetone vapors when compared to one versus ethanol
a stochastic combination of NT-to-NT contacts at each chip segment underlies the diversity of their gas-sensing properties along the array that allows us to build the chip vector signal selective to gases
the obtained layer has been positioned over the Si/SiO2 chip equipped with multiple planar electrodes
Thermal treatment of titania NTs has been performed in PEO-601 oven (ATV Technologie GmbH) in air atmosphere at 400 °C during 24 h
Following the annealing the samples have been rinsed by distilled water and dried in air
The morphological characterization of the NT array has been carried out using a scanning electron microscope (AURIGA® CrossBeam® workstation
Carl Zeiss) equipped with an energy dispersive X-ray (EDX) detector
The NT structure has been studied by transmission electron microscopy (TEM) using an aberration (image) corrected Titan 80–300 (FEI Company) equipped with a US1000 (Gatan) CCD camera
After mechanical removing the TiOx NTs from the substrate
they have been dispersed in n-heptane by sonification and deposited on a carbon coated Cu grid (Quantifoil) for the TEM analysis
For an electron tomographic characterization in HAADF-STEM mode
15 nm gold nanoparticles (University of Utrecht) were added for alignment and a tilt-series recorded from −60° to 60° in 2° steps
The tilt-series alignment was performed using IMOD (University of Colorado) and the 3D volume reconstructed using the SIRT algorithm implemented in Inspect3D (FEI Company)
The Supplementary video shows a volume rendering of the 3D structure of the NT array morphology and a surface rendering of a selected part of the 3D reconstruction prepared in Amira (FEI Company)
All spectra have been referenced to the C 1s peak of hydrocarbon at 285.0 eV binding energy controlled by means of the well-known photoelectron peaks of metallic Cu
We have tested a number of chips in preliminary studies
the reported data belong to one exemplary chip
The response of multisensor chip equipped with TiOx NT array towards different organic vapors has been studied using a setup which includes home-made data acquisition unit
gas delivery tubes and electronic unit to maintain and monitor the chip operating temperature
Data acquisition module (National Instruments USB-6259) together with current pre-amplifier (SRS
SR570) has provided the resistivity measurements up to tens GOhms of each segment in the chip
To read out the total array resistances we have employed a multiplexing card for switching between the segments
Test vapor mixtures with laboratory air have been obtained with gas generator (Owlstone
UK) which employs heated permeation tubes containing a test liquid to yield vapors of several ppm of concentration under equilibrium conditions
The vapors have fed the chip by series of 10 min duration interrupted by pulses of pure laboratory air for 10–25 minutes to ensure the recovery of the chip segment resistances
The concentration of vapors in mixture with air has been maintained to be 5
The laboratory air is delivered by an oil-free compressor as is to be of normal humidity level in range of approx
The all gases have been supplied in a flow mode with 100 sccm rate
We have utilized only the data for NT array segments with resistivity less than 10 GOhm at maximum operating temperature of 400 °C
16 segments of the multielectrode chip have been considered in the reported data
Microhotplate platforms for chemical sensor research
In Chemical sensors: comprehensive sensor technologies
Anodically grown functional oxide nanotubes and applications
In Electronic Noses and Tongues in Food Science (ed
Electronic Processes on Semiconductor Surfaces during Chemisorption (Consultants Bureau
The effect of grain size on the sensitivity of nanocrystalline metal-oxide gas sensors
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Sakharov for technical assistance on material characterization and Prof
Kolmakov (NIST) for help in reviewing the manuscript
Ministry of Education and Science for a partial support by grants no
16.1119.2017/4.6 and K3-2016-031 issued to MISiS
Ministry of Economics and Technology to support the K-Alpha + instrument
The authors thanks Karlsruhe Nano Micro Facility (KNMF
Skolkovo Institute of Science and Technology
Kotel’nikov Institute of RadioEngineering and Electronics of Russian Academy of Science
Yuri Gagarin State Technical University of Saratov
Institute of Nanotechnology and Karlsruhe Nano Micro Facility
Institute for Applied Materials and Karlsruhe Nano Micro Facility
Department of Functional Nanosystems and High-Temperature Materials
National University of Science and Technology “MISIS”
conceived the idea and designed the experiments
contributed extensively to sample fabrication
contributed to the data analysis and discussion of mechanisms involved
All authors contributed to writing the paper
The authors declare that they have no competing interests
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DOI: https://doi.org/10.1038/s41598-017-10495-8
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