Andris Šutka

Andris Šutka
Riga Technical University | RTU · Institute of Materials and Surface Engineering

Dr.sc.ing.

About

114
Publications
35,297
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,028
Citations
Introduction
Triboelectrification, nanogenerators, surface charge, plasmonic nanocrystals, photocatalysts, transparent conductive oxides, semiconductor quantum dots, soft piezoelectric materials, photochromic devices, degenerated semiconductor oxides, ZnO, TiO2, photoelectrochemical properties, oxide nanomaterials, hematite, goethite, iron oxides, visible light photocatalysts, nanoparticle colloids, electrospinning, polymer materials, polymer nanofibers, nanoporous materials, SiO2, sol-gel auto-combustion.
Additional affiliations
March 2017 - May 2017
Riga Technical University
Position
  • Principal Investigator
March 2017 - February 2023
Riga Technical University
Position
  • Head of Department
January 2014 - January 2016
University of Tartu
Position
  • PostDoc Position
Education
September 2004 - December 2012
Riga Technical University
Field of study
  • Materials Science, Chemical Technology

Publications

Publications (114)
Article
Full-text available
Straightforward and effective electrostatic charge detection would have significant relevance in electronics assembly. Electrostatic surface charges arising from contact/separation of materials with different electron affinity cause damage of electronic components and devices at a sizeable global cost, whereas the detection of such surface charges...
Article
Solid-state narrow band gap semiconductor heterostructures with a Z-scheme charge-transfer mechanism are the most promising photocatalytic systems for water splitting and environmental remediation under visible light. Herein, we construct all-solid Z-scheme photocatalytic systems from earth abundant elements (Ca and Fe) using an aqueous synthesis p...
Article
Full-text available
Although it is known that triboelectric nanogenerators (TENG) based on ferroelectric polymer films show better performance, the origin of this enhancement remains poorly understood. To date, it has been accepted that enhancement is observed to due shift of the “effective work function” of ferroelectric polymer insulator which in turn enhance electr...
Article
Full-text available
Observations on strong photochromic effect of crystalline TiO2 quantum dots (mean size ≈ 4 nm) are presented. The synthesized quantum dots consist of irregularly shaped anatase TiO2 nanoparticles (NPs) and are dispersed in butanol (8 % by mass). Obtained NPs exhibit a dramatic photoresponse to UV light, enabling effective transmittance modulation o...
Article
Full-text available
Switching adsorption-desorption by visible light would provide the possibility for a wide range of applications that require controlled release-on-demand. Here we demonstrate a visible-light controlled desorption behavior in aqueous suspensions for the first time. We observed cationic dye adsorption on amphoteric goethite α-FeOOH in the dark and re...
Article
The main requirement of triboelectric nanogenerator (TENG) device is the necessity to have separable parts to harvest mechanical energy, thus complicating the integration into energy harvesting systems. Herein we show a volumetric triboelectric generator concept – triboelectric laminate (TEL) prepared entirely from PDMS, for conversion of acoustic...
Article
Full-text available
This study reports the impact of Ca2Fe2O5 porous powder on the yeast Candida utilis—as a fungal model—at different phases of growth, i.e., early exponential (6 h), mid-log (11 h), and stationary (17 h) phases. Ca2Fe2O5 inhibited the cell growth in a time-dependent manner. After 120 min incubation, the fungicidal activity of porous powder was observ...
Article
Metal-free catalysts based on nitrogen-doped carbon are among the most promising replacements for Pt-based materials on polymer electrolyte membrane fuel cell (PEMFC) cathodes due to their inherent stability (lack of metal atoms bypasses most of the degradation mechanisms encountered in metal-based non-precious metal catalysts). However, the produc...
Article
Full-text available
When particles are mixed in polymer, particle surfaces become passivated by polymer matrix, leading to significantly reduced photocatalytic and, thus, also reduced antibacterial activity, as the catalytic particles become isolated from the outer environment and microorganisms reaching the surface. Herein, we demonstrate a facile and rapid approach...
Article
In the current study we demonstrate a method of preparation of low-density polydimethylsiloxane (PDMS) foams from emulsions by using water-based thixotropic fluids as porogens. Aqueous dispersions of synthetic hectorite clay and nanocellulose were used as thixotropic fluids, enabling the preparation of fine emulsions in bulk form with the droplet s...
Article
Triboelectrification of polymers enables mechanical energy harvesting in triboelectric generators, droplet generators, and ferroelectrets. Herein, triboelectric polymers, inspired by the ordering in spider‐silk, with strongly enhanced contact electrification are presented. The ordering in polyether block amide (PEBA) is induced by the addition of i...
Article
Photochromic materials can be used for modulation of the visible and infrared light transmittance for providing privacy or energy saving by blocking the heat. Titanium dioxide (TiO2) nanoparticles has been well reported as a promising photochromic material. However, a high photochromic response from TiO2 can be observed only when the nanoparticles...
Article
Full-text available
In the amphoteric membrane-less decoupled water electrolysis, hydrogen and oxygen are co-produced in separate cells with higher energy efficiency. Ion exchange is mediated by the auxiliary electrodes – H x WO 3 for acid and NiOOH for alkaline cell.
Article
Water disinfection is a crucial challenge for humanity. Approaches that are effective, cheap, environmentally friendly, and do not promote gene exchange between bacteria are urgently required. Strongly oxidizing radicals are highly promising to achieve this as they lead to bacterial activation at high efficiencies. However, sources to consistently...
Article
Full-text available
In the current study we show that the combustion of sol-gel derived alcogels with specifically tailored composition leads to the release of silica nanoparticles from the burning alcogel in a controlled manner which enables direct deposition of the released nanoparticles into low-density silica thick films. The process has some similarities to flame...
Article
Heteroatom doped metal-free catalysts are one of the most promising replacements for platinum for the alkaline oxygen reduction reaction (ORR). Due to the lack of metal atoms, they are extremely stable and environmentally friendly. However, production of carbon nanomaterials can have a very high CO2footprint. In this study, we present ORR catalysts...
Article
The main requirement for triboelectric nanogenerator devices is the necessity to have separable or movable parts to harvest mechanical energy, thus complicating their integration into the energy harvesting systems. Herein, triboelectric laminates that show a volumetric electromechanical response are introduced, similar to intrinsic ferroelectric po...
Article
In this study, we investigate triboelectrification in polymer-based nanocomposites using identical polymer matrixes containing different concentrations of nanoparticles (NPs). The triboelectric surface charge density on polymer layers increased as the difference in nanoparticle filler concentration between the two triboelectric layers escalated, de...
Article
Full-text available
In the current study, the antibacterial activity of positively and negatively charged spherical hematite (α-Fe2O3) nanoparticles (NPs) with primary size of 45 and 70 nm was evaluated against clinically relevant bacteria Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) as well as against naturally bioluminescent bacteria Vi...
Article
Detection of volatile organic compounds (VOCs) at room temperature in an ambient environment is highly desired, but still a distant function for gas sensor materials. Here, we are demonstrating a photodoping-inspired gas sensing approach based on a thin solid film made of ultrasmall (<5 nm) TiO2 nanoparticles. The gas sensing material has been acti...
Article
Drying of sol-gel alcogels at ambient conditions leads to shrinkage and cracking due to differential capillary pressure making it difficult to obtain low-density materials. Capillary pressure depends on the surface tension of the liquid, which decreases as the temperature increases and becomes zero at a critical temperature in case of commonly used...
Article
Understanding photochromicity is essential for developing new means of modulating the optical properties and optical response of materials. Here, we report on the synthesis and exciting new photochromic behavior of Nb5+ doped TiO2 nanoparticle colloids (NCs). We find that, in hole scavenging media, Nb5+ doping significantly improves the photochromi...
Article
Full-text available
Polydopamine (PDA) is a new biocompatible material, which has prospects in biomedical and sensor applications. Due to functional groups, it can host wide range of biomolecules. ZnO nanostructures are well known templates for optical sensors and biosensors. The combination of ZnO and PDA results in a change of optical properties of ZnO-PDA composite...
Article
Full-text available
Piezoelectric polymers are emerging as exceptionally promising materials for energy harvesting. While the theoretical figures of merit for piezoelectric polymers are comparable to ceramics, the measurement techniques need to be retrofitted to account for the different mechanical properties of the softer polymeric materials. Here, how contact electr...
Article
Full-text available
The hematite photo-Fenton catalysis has attracted increasing attention because it offers strong oxidation of organic pollutants under visible light at neutral pH. In the present work, aqueous synthesis of hematite photo-Fenton catalysts with high activity is demonstrated. We compare photo-Fenton activity for hematite obtained by hydrolyzation at 60...
Article
There has recently been a renewed interest in the photochromic properties and uses of TiO2 as a potential candidate for smart windows. However, the surrounding medium for TiO2 nanoparticles (NPs), is of equal importance, as it facilitates hole scavenging and, in turn, the photochromism. Here we investigated the impact of scavenging power on the pho...
Article
Polymer contact electrification offers the possibility to harvest mechanical energy using lightweight, flexible and low-cost materials, but the mechanism itself is still unresolved. Several recent studies confirm heterolytic covalent bond breaking as the mechanism for surface charge formation. Here it is shown that the reason for the formation of s...
Article
Donor dopants in oxide semiconductors are compensated not only by valuable electrons but also by other point defects, leading to decrease in electric conductivity and infrared absorption. We demonstrate that...
Article
Full-text available
Embedding additional ferroelectric dipoles in contacting polymer layers is known to enhance the performance of triboelectric nanogenerator (TENG) devices. However, the influence of dipoles formed between the triboelectric surface charges on two contacting ferroelectric films has been ignored in all relevant studies. We demonstrate that proper atten...
Article
Full-text available
In this work, we present conductometric gas sensors based on p-type calcium iron oxide (CaFe2O4) nanoparticles. CaFe2O4 is a metal oxide (MOx) with a bandgap around 1.9 eV making it a suitable candidate for visible light-activated gas sensors. Our gas sensors were tested under a reducing gas (i.e., ethanol) by illuminating them with different light...
Article
In the present work, the contact electrification of polymers that differ in adhesion strength is studied. Electrical current is measured along with adhesion in macroscale contacting‐separation experiments. Additionally, local adhesion and roughness are studied with atomic force microscopy to get deeper insight into relations between surface propert...
Article
Full-text available
Nanocomposites of manganese ferrite and bismuthoxidechloride weres ynthesized.The composites consisted of 10 nm thick nanocrystalline bismuthoxidechloride thin film grown by atomic layer deposition on spinel MnFe2O4 nanoparticles prepared by wet chemical synthesis. The composite layers exhibited nonlinear polarization behavior in both magnetic and...
Article
Molecularly imprinted polymers are important tools for the design of sensors and other molecular recognition based analytical systems. In this paper the development of a photoelectrochemical sensor for selective bisphenol determination is reported. The sensor is based on a glass/ZnO/MIP‐Ppy structure consisting of glass modified by a ZnO layer (gla...
Article
Here we report an order of magnitude increase of charge density of glassy polymers such as polystyrene (PS), polycarbonate (PC) and poly(methyl methacrylate) (PMMA) when heated above the glass transition temperature. Transition is accompanied by the larger force required for separation. Undeniably, surface roughness plays a great role in contact el...
Article
The key parameter for degenerated semiconductor oxide plasmonic nanocrystals is the doping level. Hydrothermal and solvothermal approaches are considered to be less effective towards achieving high concentration of aliovalent donor dopants in a host oxide when compared to other synthesis methods that use long chain hydrocarbon solvents, fatty acids...
Article
The contact electrification of polymer interfaces opens energy harvesting function for triboelectric (nano)generators (TEG). The electron transfer between contacted-separated surfaces has been considered as the main electrification mechanism for polymers in TEG. The electron transfer mechanism requires to contact chemically different materials, as...
Article
In order to study the influence of itinerant electrons on magnetic properties of transition metal substituted ZnO nanocrystals, nanopowders containing different amounts of Ga and fixed amounts of Fe, Ni and Mn ions were synthesized. The ions of different transition metals and Ga were successfully introduced into the ZnO structure using solvothermal...
Article
It was recently reported that more efficient triboelectric nanogenerator (TENG) like devices can be prepared using inversely polarized ferroelectric films made of same material as the contacting layers. In the present work, a clear correlation between the piezoelectric response of inversely polarized ferroelectric PVDF/BaTiO3 nanocomposite films an...
Article
This study describes a straightforward Ca2Fe2O5 brownmillerite nanopowder and thin film synthesis by the water-based sol-gel auto-combustion method. The material characterization results confirmed the phase pure narrow bandgap Ca2Fe2O5 nanoparticle formation. The surface area of synthesized nanopowder was 13.55 m²/g. Powders at loading 1 g/l exhibi...
Article
Nitrogen and sulfur co-doped carbon catalysts were prepared as electrocatalytic materials for the oxygen reduction reaction (ORR). Herein, we propose a novel and effective one-pot synthetic approach to prepare NS-doped carbon catalyst by using the mixture of graphene oxide and multi-walled carbon nanotubes as a carbon support. Successful NS-doping...
Article
Full-text available
Narrow operational voltage window can be considered as one of the greatest limitations for aqueous polymer electrolytes. Using freeze-thaw hydrogel preparation method we have synthesized wider potential window electrolytic polyvinyl alcohol (PVA)/Na2SO4 and PVA/K2SO4 electrolytes. Supercapacitors (SC) have been assembled using novel porous polyisop...
Article
Full-text available
Gas sensors based on CaFe2O4 nanopowders, which are p–type metal oxide semiconductor (MOX), have been fabricated and assessed for ethanol gas monitoring under visible light activation at room temperature. Regardless of their inferior sensitivity compared to thermally activated counterparts, the developed sensors have shown responsive sensing behavi...
Article
Full-text available
Polydimethylsiloxane (PDMS) is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological properties. PDMS has found extensive usage in various fields ranging from microfluidics and flexible electronics to cosmetics and food industry. In certain applications, like e.g. dry adhesives or dry transfer of...
Article
One of main reasons of the Joint European torus (JET) transformation from the carbon (JET-C) to ITER-like (JET-ILW) wall was high tritium retention of carbon. In order to compare the tritium retention, samples of analogous positions of the plasma-facing side of vertical tiles No. 3 of two campaigns: JET-C (2008–2009) and JET-ILW (2011–2012) were cu...
Article
While single compound semiconductors were initially used for photocatalysis, combining two compounds to form a heterojunction significantly increases the photocatalysis performance. This review will outline how heterojunctions are superior, explain the different heterostructure architectures assembled from nanoparticles, and discuss the importance...
Article
Full-text available
Optical properties of diluted narrow band gap magnetic semiconductor nanowire colloids are controlled by modest magnetic fields under 100 Oe. High aspect ratio NiFe2O4 nanowires are used to achieve responsiveness to magnetic field, light absorption and -scattering. Visible light reflectance of the diluted colloids can be either increased or decreas...
Article
Full-text available
Application of efficient antimicrobial surfaces has been estimated to decrease both, the healthcare-associated infections and the spread of antibiotic-resistant bacteria. In this paper, we prepared ZnO and ZnO/Ag nanoparticle covered surfaces and evaluated their antimicrobial efficacy towards a Gram-negative bacterial model (Escherichia coli), a Gr...
Article
The aim of this work is to study pressure sensing effect of the developed flexible solid-state supercapacitor which uses conductive carbon black/polyisoprene composite electrode and PVA/H3PO4 electrolyte. Electrochemical characterization of supercapacitor has been performed to evaluate the performance of the supercapacitor as energy storage device...
Article
Here we are reporting solvothermal synthesis derived diluted magnetic and plasmonic Co-Ga co-doped ZnO nanocrystals with high magnetization values (from 1.02 to 4.88 emu/g) at room temperature. Co-Ga co-doped ZnO nanocrystals show up to 2 fold increase in saturation magnetization compared to Co doped ZnO nanocrystals at the same Co concentration, w...
Article
We investigate yttrium-doped hematite thin-film photoelectrochemical properties and find yttrium incorporation to amply improve the performance as a photoanode for water splitting under visible light. We used the spray pyrolysis method to prepare a set of yttrium doped Fe2-xYxO3 (x = 0, 0.05, 0.10, 0.15, 0.2) thin films (thickness below 500 nm) on...
Article
Liquid phase deposition polymerization (LPDP) is a recently reported method suitable for preparation of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), with some similarities to vapor phase polymerization except the polymer film growth at the gas-solid boundary is replaced with growth at the liquid-solid interfacial layer. Film gro...
Article
We are presenting highly porous ethyl cellulose (EC) nanostructured films for triboelectric nanogenerator (TENG) contact layer material with high performance for converting mechanical energy to electricity. Homogeneous porous EC films were deposited on conductive substrate in less than one minute without need for specific equipment. EC triboelectri...
Article
Electric field created by the nearby electrostatic charge orients the colloidal nanowires in the medium of low dielectric constant, causing a visible color change. We show that the kinetics of subsequent color restoration correlates well to ambient relative humidity. Presented principle could be used for detecting humidity, which affects net surfac...
Article
Triboelectric generators (TEGs) are devices that convert mechanical energy to electrical energy through triboelectric charging of different material surfaces at periodic contact. Typically, such devices consist of two dielectric contacting layers with electrodes attached on the non-contacting sides but alternatively, one material can simultaneously...
Article
We have developed magnetically separable and reasonably stable visible light active photocatalysts containing CoFe2O4 and mixture of Ag2O/Ag2CO3 nanoheterostructures. Obtained ternary nanoheterostructures outperform previously reported magnetically separable visible light photocatalysts, showing one of the highest visible light photocatalytic dye d...
Article
Full-text available
Colorimetric gas sensing is demonstrated by thin films based on ultrasmall TiO2 nanoparticles (NPs) on Si substrates. The NPs are bound into the film by p-toluenesulfonic acid (PTSA) and the film is made to absorb volatile organic compounds (VOCs). Since the color of the sensing element depends on the interference of reflected light from the surfac...
Article
We report the mechanical performance of α-FeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (α-FeOOH) nanocrystals have a high elastic modulus and –OH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Need...
Article
In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force mi...
Article
A novel method for the preparation of thick silica foam films is reported that combines an alkoxide-based hydrolytic sol–gel process and in situ catalytic decomposition of hydrogen peroxide on a catalyst-coated support. A hydrogen peroxide/nitric acid aqueous solution was used to carry out acid-catalysed hydrolysis of tetramethoxysilane. Complete s...
Article
Full-text available
The influence of lignocellulosic nanofibers (LCNF) additive on the inherent mechanical properties of submicron electrospun poly(vinyl alcohol) (PVA) fibers is reported. LCNF with a diameter of 25±15 nm and a length of 220±90 nm obtained from hemp shives were dispersed in aqueous PVA solutions to produce homogeneous nanocomposite fibers with 0, 5, a...
Article
In the present work, we demonstrate a novel approach to nanotribological measurements based on the bending manipulation of hexagonal ZnO nanowires (NWs) in an adjustable half-suspended configuration inside a scanning electron microscope. A pick-and-place manipulation technique was used to control the length of the adhered part of each suspended NW....