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Functionalized carbon dots on TiO2 for perovskite photovoltaics and stable photoanodes for water splitting
摘要： Various types of fluorescent carbon nanoparticles, often called carbon dots (CDs), are synthesized by different polycondensation methods: microwave irradiation, hydrothermal conditions or solution chemistry at ambient temperature with subsequent chemical functionalization. The CDs are deposited on TiO2 films to be probed as electron transport layers in perovskite photovoltaics and the anode for photoelectrochemical water splitting. Nitrogen CDs, which do not contain oxygen, lead to an increase of around 50 mV in the open circuit voltage of perovskite solar cells. All the CD types produce an improved photocurrent in water splitting, particularly CDs that are functionalized with thiol groups and butyl chains. It is demonstrated that the modified electrode is stable under continuous operation. Other electrochemical characteristics of the electrode, such as the voltammogram shape, onset potentials and open circuit potentials, remain nearly unchanged upon the deposition of CDs. Only the incident photon to current conversion efficiency improves clearly, extending the absorption range by around 20 nm towards longer wavelengths. This study provides new data about mechanisms and electrode arrangements for improving the performance of n-type semiconductors in photovoltaic cells and photoelectrochemical hydrogen production.
关键词： Sustainability,Titanium dioxide,Renewable hydrogen,Carbon nanoparticle,Solar energy
更新于2025-09-23 15:19:57
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Mid-Infrared Electro-Optical Modulation Using Monolithically Integrated Titanium Dioxide on Lithium Niobate Optical Waveguides
摘要： tunable photonic circuits were demonstrated in the mid-infrared (mid-iR) regime using integrated tio2-on-Linbo3 (toL) waveguides. the upper waveguide ridge was made by a sputtered tio2 thin film with broad transparency at λ = 0.4–8 μm and an optimized refractive index n = 2.39. The waveguide substrate is a z-cut single crystalline Linbo3 (LN) wafer that has strong Pockels effect, thus enabling the tunability of the device through electro-optical (e-o) modulation. A sharp waveguide mode was obtained at λ = 2.5 μm without scattering or mode distortion found. The measured E-O coefficient γeff was 5.9 pm/V approaching γ31 of 8.6 pm/V of LN. The ToL waveguide showed a hybrid mode profile where its optical field can be modified by adjusting the TiO2 ridge height. our monolithically integrated ToL modulator is an efficient and small footprint optical switch critical for the development of reconfigurable photonic chips.
关键词： electro-optical modulation,lithium niobate,optical waveguides,mid-infrared,titanium dioxide
更新于2025-09-23 15:19:57
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Transmission IR cell for atmosphere-controlled studies of photoprocesses on powdered high surface area materials
摘要： Up to now, FT-IR spectroscopy remains one of the most effective techniques employed in the research of various heterogeneous processes including catalysis and photocatalysis. Here, the construction of a newly developed cell designed to conduct in situ IR spectroscopic studies of photoprocesses on powdered adsorbents in the transmission mode is presented. The capabilities of this device are illustrated by experimental data on photoinduced processes involving well known photocatalysts such as titanium dioxide. In particular, the kinetics of the UV-induced spectroscopic alterations in the IR spectrum of hydrated TiO2 were obtained and analyzed. Moreover, the photoactivated desorption of carbon monoxide at ambient temperature from the dehydrated TiO2 surface was observed and plausible explanations were proposed.
关键词： photoprocesses,in situ studies,FT-IR spectroscopy,photocatalysis,titanium dioxide
更新于2025-09-23 15:19:57
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Dye Engineered Perovskite Solar Cells under Accelerated Thermal Stress and Prolonged Light Exposure
摘要： Herein, the thermal and light stability enhancement of planar perovskite solar cells (PSCs) based on the approach of dye-sensitization of the titania compact layer with the triphenylamine-based metal-free organic (E)-3-(5-(4-(bis(2’,4’-dibutoxy-[1,1’-biphenyl]-4-yl) amino) phenyl) thiophen-2-yl)-2-cyanoacrylic acid (D35) dye is reported. The D35 molecule is chemically adsorbed via a bidentate anchor group upon the TiO2 underlayer. This enhances the power conversion efficiency of PSCs due to its well-established versatile role, offering facilitation of electron charge transfer to the anode while favoring the growth of robust and homogenous perovskite layers. However, its influence in the PSC performance seems to expand further. The stability experiments showed an enhanced endurance for the devices after the insertion of D35, not only in shelf-shield conditions but also after accelerated thermal tests and prolonged light exposure. This study confirms the plethoric role of dye sensitization strategy and its advantages to interfacial engineering via organic chromophores towards efficient and stable PSCs.
关键词： dyes/pigments,perovskite solar cells,titanium dioxide,perovskite phases,stability enhancement
更新于2025-09-23 15:19:57
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White Painting Pigment as a Low-Cost Light Scattering Material for Bilayer Photoelectrodes of Dye-Sensitized Solar Cells
摘要： White pigment (DuPont R902+) has been used as a light scattering material in the preparation of bilayer photoelectrodes of dye-sensitized solar cells (DSCs). The X-ray diffraction (XRD) pattern of the white pigment revealed that the material consists of rutile phase of titanium dioxide. The light scattering layer prepared from the white pigment was coated onto the main-layer of the photoelectrodes of DSCs. The solar cells with and without light scattering layer were tested in the simulated light of 100 mW/cm2. The DSCs with the light scattering layer generated more current density than the DSCs without scattering layer and the overall light to electric power conversion efficiency of DSCs with the light scattering layer was ~4.00 % compared with 3.25 % efficiency of the DSCs without the scattering layer.
关键词： Dye-sensitized solar cell,Photoelectrode,Light scattering layer,Transmittance,White pigment (R902+),Rutile titanium dioxide
更新于2025-09-23 15:19:57
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Dip coated TiO2 based metal-semiconductor-metal ultraviolet photodetector for UV A monitoring
摘要： Metal-Semiconductor-Metal ultraviolet photodetector was fabricated by painting silver contacts on dip coated TiO2 thin films. The number of deposition cycles have influence on physiochemical properties and UV sensing properties. The UV photodetector properties were studied by illuminating devices with light intensity of 1.8 μW/cm2 and 5 V bias. The fabricated devices show ohmic I–V characteristics. The maximum photocurrent of 0.64 μA is obtained at 365 nm for film deposited at 8 cycles. The highest photoresponsivity obtained for C8 sample under UV illumination of 365 nm is 2.15 A/W at 5 V bias. The fast rise and fall times obtained for fabricated device are 17 s and 19 s. The optical switching characteristics show good reproducibility and stability.
关键词： Photoresponsivity,Dip coating,MSM UV photodetector,Titanium dioxide
更新于2025-09-23 15:19:57
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Development of Pd/TiO2 Porous Layers by Pulsed Laser Deposition for Surface Acoustic Wave H2 Gas Sensor
摘要： The influence of sensitive porous films obtained by pulsed laser deposition (PLD) on the response of surface acoustic wave (SAW) sensors on hydrogen at room temperature (RT) was studied. Monolayer films of TiO2 and bilayer films of Pd/TiO2 were deposited on the quartz substrates of SAW sensors. By varying the oxygen and argon pressure in the PLD deposition chamber, different morphologies of the sensitive films were obtained, which were analyzed based on scanning electron microscopy (SEM) images. SAW sensors were realized with different porosity degrees, and these were tested at different hydrogen concentrations. It has been confirmed that the high porosity of the film and the bilayer structure leads to a higher frequency shift and allow the possibility to make tests at lower concentrations. Thus, the best sensor, Pd-1500/TiO2-600, with the deposition pressure of 600 mTorr for TiO2 and 1500 mTorr for Pd, had a frequency shift of 1.8 kHz at 2% hydrogen concentration, a sensitivity of 0.10 Hz/ppm and a limit of detection (LOD) of 1210 ppm. SAW sensors based on such porous films allow the detection of hydrogen but also of other gases at RT, and by PLD method such sensitive porous and nanostructured films can be easily developed.
关键词： bilayer films,pulsed laser deposition (PLD),palladium,hydrogen sensor,surface acoustic wave (SAW),Pd/TiO2,porous morphology,titanium dioxide
更新于2025-09-23 15:19:57
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Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide
摘要： Nanostructured TiO2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces. These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO2. It is shown for the first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance.
关键词： reduced graphene oxide,photoelectrodes,titanium dioxide,photoelectrochemistry,hole-transport layer
更新于2025-09-23 15:19:57
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An Environmentally Friendly Method for Testing Photocatalytic Inactivation of Cyanobacterial Propagation on a Hybrid Ag-TiO2 Photocatalyst under Solar Illumination
摘要： Cyanobacteria were inactivated under sunlight using mixed phase silver (Ag) and deposited titanium dioxide (TiO2) coated on the surface of diatomite (DM) as a hybrid photocatalyst (Ag-TiO2/DM). The endpoints of dose-response experiments were chlorophyll a, photosynthetic efficiency, and flow cytometry measurements. In vitro experiments revealed that axenic cultures of planktonic cyanobacteria lost their photosynthetic activity following photocatalyzed exposure to sunlight for more than 24 h. Nearly 92% of Microcystis aeruginosa cells lost their photosynthetic activity, and their cell morphology was severely damaged within 24 h of the reaction. Preliminary carbon-14 (14CO3^2-) results suggest that the complete inactivation of cyanobacteria arises from damage to cell wall components (peroxidation). A small concomitant increase in cell wall disorder and a consequent decrease in cell wall functional groups increase the cell wall fluidity prior to cell lysis. A high dosage of Ag-TiO2/DM during photocatalysis increased the concentration of extracellular polymeric substances (EPSs) in the Microcystis aeruginosa suspension by up to approximately 260%. However, photocatalytic treatment had a small effect on the disinfection by-product (DBP) precursor, as revealed by only a slight increase in the formation of trihalomethanes (THMs) and haloacetic acids (HAAs).
关键词： titanium dioxide,silver,extracellular polymeric substances,photocatalysis,disinfection by-products,cyanobacteria
更新于2025-09-19 17:15:36
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Iron and the other metal species as phase-composition controllers the photocatalytic activity of TiO2 materials
摘要： The goal of the work is to verify which properties of TiO2-based materials, influenced by small amounts of Fe, Co, Ga, Bi, W, Mo, V and Ni species used as modifiers, play the predominant role in changing the photoactivity of TiO2. Two groups of materials were studied: TiO2 synthesized in the presence of nanocrystalline metal oxide and dissolved metal ions (cations or oxyanions). Sols were calcined at 450, 600 or 900°C. Physicochemical properties of the materials were characterized by XRD, DRS, SEM, EPR, porosimetry and photocurrent measurements. The most detailed studies were focused on modifications by iron species. TiO2 doping was achieved for both Fe3+ and Fe2O3 modifiers after calcination at temperatures equal to or higher than 450 and 900°C, respectively. Morphology of the materials (phase composition, specific surface area, etc.) were influenced by iron species even if they were not introduced into the crystal lattice of TiO2. Comparison of activity of photocatalysts and elucidation of the role of various reactive oxygen species were based on photooxidation tests involving Azure B and terephthalic acid. In general, iron species improved photocatalytic activity, nevertheless, doping of the materials appeared detrimental. A particular improvement of the activity was achieved for composites with low iron contents (ca. 0.01%mol Fe:Ti). The studies revealed, that beside the widely discussed mechanisms (photo-Fenton processes, charge separation, photosensitization, etc.) iron species can indirectly influence the photocatalytic activity of TiO2 acting as phase-composition controllers (PCC) during the synthesis of this oxide, which determine morphology of the resulting photocatalyst. To support this hypothesis, several sets of other TiO2 materials were modified with Co, Ga, Bi, W, Mo, V and Ni species. We show, that the use of these modifiers in small amounts can influence indirectly the activity of photocatalysts regardless to the type of modifier. Therefore different photoactivity of the tested materials should be attributed rather to these modifier-induced structural and electronic changes of the photocatalysts than to any other function of dopants, including photosensitization, enhanced charge separation, catalytic activity, at which most of studies are focused.
关键词： phase composition,photocatalysis,synthesis of photocatalysts,modified titanium dioxide
更新于2025-09-19 17:15:36