2025

Title Laser-induced Formation of TiO2 with Controllable
Phase on the Surface of Titanium

1000000

610.2 cm-1636.2 cm-1516 cm-1397 cm-1

200446.5 cm

610.1 cm-1

-1

238.2 cm-1

144.1 cm-1

100
100

Titanium dioxide (TiO2) is a wide band gap metaloxide semiconductor with numerous applicationsin science and technology [1]. The main fields arephotovoltaic and photo catalytic for water
purification. TiO2 is known to form manypolymorph phases, but the most studied TiO2
polymorph phases are anatase, rutile andbrookite. It is known that the anatase is morefavorable for photo catalytic applications, while
the rutile exhibits better optical and electricalperformance [2]. In recent years, researchers
started to focus on anatase/rutile heterostructures,
which showed improved photo catalytic efficiency.
In this study, the effects of laser radiation on TiO2
crystal were investigated with aim to show thepossibility of phase transition from rutile toanatase.
Nb:0.05wt% doped TiO2 crystal was used inexperiments. The crystal was irradiated by
fourth harmonic of Nd:YAG laser withfollowing parameters: λ=266 nm, τ=3 ns,intensity I=56.0 MW/cm2. The sample wasirradiated in one spot from 1 till 10000 laser
pulses. From Raman scattering spectra, it canbe seen that the crystal consists of rutile phase

241 cm-1

200.1 cm-1

10000

1000

［２］Research Progress（10.5 points）

445 cm-1

144.3 cm-1

Non-IrradiatedIrradiated 100 pulses
Irradiated 1000 pulses
Irradiated 10000 pulses

100000Intensity, arb.units［１］Organization（10.5 points）
Project Leader：Prof. Arturs Medvids（Riga Technical University）
Representative at RIE：Prof. Hidenori Mimura（ Research Institute of Electronics,
Shizuoka University, Japan）
Participants：Dr. Edvins Dauksta（Riga Technical University）

before the irradiation (Fig.1). After irradiation
the crystal is transformed in to the anatase
phase, as can be seen in Raman scattering
spectra [3].

300400500

600

700

800900Raman shift, cm-1

Fig.1. Raman spectra of TiO2 thin films before
and after irradiation by the fourth harmonic ofNd:YAG laser at I=56.0 MW/cm2.
References[1] M. Grätzel, Nature 414, 338 (2001).
[2] H. Cheng and A. Selloni, Phys. Rev. B 79,092101 (2009).
[3] H.L.Ma, J.Y.Yang et al. Appl.Surf. Sc. 253,7497(2007)［３］Results（10.5 points）(３－１) Research results
We were planning elaborate laser technology ofTiO2 thin film formation with controllable
phase on the surface of titanium plate. Dependon laser parameters: intensity, wavelength andpulse duration, TiO2 thin film will be indifferent phases. For characterization of theobtained thin films the following equipment
will be used: Nd:YAG laser, SEM, AFM, FTIR,
Raman and optical spectrometers.
This work is connected with medicine, biologyand physics.

Preparation of the samples
Cleaned Ti substrate was secured on sample table.
Laser (Q-switched nanosecond Nd:YAG laser
Ekspla Nl301G, λ = 1064 nm ) with top hat beamprofile was used to irradiate samples. Focusedlaser pulse mode (τ = 6 ns) with pulse energy of 33
mJ was used. The sample was irradiated with 53
MW/cm2 in ambient air atmosphere (Fig.2.).
Sample irradiation was performed by scanning
the sample with laser spot size of 0.44 mm2 andscanning speed of 220 µm/s. Under rapid heat oflaser radiation natural TiO2 is evaporated
opening clean Ti surface, where by adsorbing
atmosphere oxygen TiO2 is formed.
(a)Fig.2 TiO2 thin film formed by Nd:YAG laser
radiation with different dose.
Microbiological activity
Bacterial colonisation intensity was tested using
Staphylococcus epidermidis (S.epidermidis)(ATCC 12228) and Pseudomonas aeruginosa(P.aeruginosa) (ATCC 27853) bacteria reference
cultures.
Determining microorganism colonisation in vitro
We prepared 1 ml TSB (Triptycase soy broth)(Oxoid, UK) bacterial suspensions from bacterial
pure cultures in concentration of 102 CFU/ml. In
order to determine colonisation intensity, samples
were cultivated at 37°C for 24 h. Unattachedmicroorganisms after incubation were rinsed off.
Samples were processed in ultrasound bath(Cole-Palmer, USA) for 1 minute (at 45 kHz
frequency) at maximum velocity in Vortex
centrifuge (Biosan, Latvia), in order to separate
attached bacteria from the surface of the sample.
Three cultures were produced on TSA (Triptycasesoy agar) (Oxoid, UK) from each sample, and they
were cultured for 24 hours in 37°C, in order todetermine the total amount of microorganisms
per sample area.
We found out in the study that the colonization
intensity of S. epidermidis and P.aeruginosa isincreased
or decreased
depends on thesamples used in the study.

(b)
Fig.3. The colonization intensity of S. epidermidis(a) and P.aeruginosa (b).
Photocatalytic activity studies.
For the determination of photocatalytic activity,
the samples where immersed in 30 mL of asolution of methyl-orange (MO) with aconcentration of 0.034 mM. The samples wherethen irradiated for 10 hours using a 100W
High-pressure mercury lamp with a peakwavelength of 365 nm and an irradiance of 20mW/cm2. The samples were cooled using anarray of 120 mm fans and heatsinks in order tomaintain a constant temperature. After each houra sample of 1 mL was taken from the reaction
vessel. Changes in concentration of MO wheredetermined using a UV-Vis spectrophotometer(Gensys 10S) by measuring the absorbance at 465
nm. A darkness test was also conducted toevaluate the adsorption of MO on the samplesurface.

Fig.4. Methyl orange degradation dependence on
method of TiO2 layer formation onTi substrate.

Fig.5. Surface energy of the TiO2/Ti structure
formed by the laser radiation dependence on TiO2thickness.
Conclusion
We have found that irradiation of TiO2 single
crystal by nanosecond laser with λ=266 nm,I=46.0 MW/cm2 and 10000 pulses leads to thepartial conversion of rutile to anatase.
We found out in the study that the colonization
intensity of S. epidermidis and P.aeruginosa isincreased
or decreased
depends on thesamples used in the study.

(３－２) Ripple effects and further developments
Exchange of scientific expertise between theparticipants was very helpful for coordination ofexperimental work towards the goal of thisproject. Also, it has contributed to strengtheningof domestic and international collaboration at
Research Institute of Electronics. Joint work anddiscussions between the participants of thisproject have broadened the scope of existing
domesticandinternational
research
collaborations at RIE, as well as opened newvenues for collaboration in the future.
［４］Achievements (List of Publications)（10.5
points）（１）A.Medvid’, P. Onufrijevs, E. Dauksta, H.
Mimura “Phase Transitions in Metal Oxide
Semiconductors Induced by Laser Radiatin”,
Materials
ofScientificandTechnicalConference.Laser Technologies.Lasers and Their
Application., June 7-9, Truskavets, Ukraine, pp.
96-98, 2017.
（２）T. Potlog, E. Dauksta, A. Medvids, L.
Ghimpu, C. Moise, K. Murakami, H. Mimura,
EFFECT OF LASER IRRADIATION ON THE
REFRACTIVE INDEX OF THE TiO2 THINFILMS, Submitted to Optics and Laser
Technology Journal.

Travelling Report（Mention each travel by CRP budget.）Name：Prof. Arturs Medvids
Affiliation：Riga Technical University
Period of time：15.10.2017-04.11.2017.
Destination：Shizuoka University, Japan
Purpose：To carry out a joint research, plan the future collaboration, participate at the workshop
and report previously obtained results.
Name of receiver：Prof. Hidenori Mimura