Hamdi Şükür Kiliç

Femtosecond laser induced photodynamic therapy on 5-ALA treated SKMEL-30 cells: An efficient theranostic strategy to combat melanoma

PURPOSE Photodynamic therapy (PDT) is a type of photo-chemotherapy that is based on the application of photosensitizer and irradiation of the region by laser sources. Photosensitizer and light interaction will develop reactive oxygen radicals ((1)O2) in the cells and elimination of cells by apoptosis or necrosis. METHODS Metastatic skin cancer cells SKMEL-30 were treated by 5-ALA in dark and then they were irradiated by 90-femtosecond (fs) laser with different pulse powers for different durations. The effects of 5-ALA mediated photodynamic therapy on the cells were determined by XTT proliferation kit and by flow cytometry measurements of Annexin V, 7-AAD and mitochondrial membrane potential alterations. Fluorescent accumulation of protoporphyrin IX was investigated by fluorometry and confocal laser microscope. RESULTS The viability tests for SKMEL-30 cells treated with different 5-ALA doses and femtosecond laser power and durations demonstrated that 635 nm, 45 mW pulse energy at 90 fs laser pulse applications for 60 sec to 1mM 5-ALA exposed cells decreased the cell proliferation by 30%. Flow cytometric measurements exhibit that PDT caused 63% of mitochondria membrane potential alteration, 30% of cell death in the population by apoptosis and 39% of cells by necrosis. There was 1mM 5-ALA exposure that also exhibited about 32% accumulation of fluorescence in the cells. CONCLUSION The pretreatment of the cells with the precursor 5-ALA lets the imaging due to increased protoporphyrin IX fluorescence. This treatment method may be proposed as an effective theranostic strategy for melanoma because of its rapid and effective anticancer consequences.

Plasmonic tuning of gold doped thin films for layers of photovoltaic devices

In order to increase the absorption rates in solar cells, increasing research activities on the plasmonic nanostructures are followed carefully. The plasmonic nanoparticles provides an important enhancement in the trapping of photons in the active layer of the solar cells by means of interaction between incident light and plasmonic nanoparticles. In order to obtain this approach, under of 5×10−4 mbar and 1×10−2 mbar ambient argon gas pressure, gold thin film was deposited on the silicon substrate by applying PLD system. The morphology of thin films obtained was investigated by AFM and SEM considering the effect of Ar gas pressure on the plasma plume. SPR peaks for Au nanoparticles deposited under 5×10−4 mbar and 1×10−2 mbar Ar gas pressure were observed at 756 nm and 658 nm wavelengths respectively. It has been stated that the SPR peak in the infrared is depend on the near field interaction between Au nanoparticles. Furthermore, when the pressure is increased to 1×10−2 mbar Ar, it has been observed that t...

A mass spectrometric investigation of isomers of butane

RATIONALE Butane is an important industrial chemical in which photo-processes are very important for the initiation of reactions. Recent advances in nanosecond pulsed laser technology have led to high laser intensities being available to researchers to enable these photo-processes to be studied in compounds such as butane. METHODS The photo-decomposition, dissociation and combustion mechanisms in the neutral butane molecule have been studied in detail, by investigating the multiphoton (MP) dissociative ionisation of its n- and i-isomers, using a time-of-flight mass spectrometer connected to a high power nanosecond laser system. The laser used was a Nd:Yag with a 5 ns pulse width operated at the fundamental wavelength (1064 nm) and the doubled and tripled wavelengths (532 nm and 355 nm). The fragmentation patterns for the isomers were determined for the three wavelengths as a function of laser intensity. Similar laser intensities of between 10(10) and 10(13) W/cm(2) were used at the three wavelengths: 1064, 532 and 355 nm. RESULTS The mass spectra of each isomer of the butane molecule display a very weak molecular ion and are dominated by fragment ion peaks. The degree of fragmentation increases as the laser intensity increases. CONCLUSIONS Depending on the wavelength some significant differences in the mass spectra of the two isomers were detected and it has been concluded that the isomerisation of i-butane to n-butane is a process which is faster than the duration of the laser pulse used.

Analysis of Current-Voltage-Temperature and Capacitance-Voltage-Temperature Characteristics of Re/n-Si Schottky Contacts

The current–capacitance-voltage characteristics of Re/n-type Si Schottky contacts have been measured in the temperature range of 60–300 K by steps of 20 K. The ohmic and Schottky contacts are made by the Pulsed Laser Deposition (PLD) technique. The values of barrier heights, ideality factors and serial resistances have been found to be strongly temperature dependent. In short, the ideality factor decreased and the barrier height increased with increasing temperature, when the temperature-dependent (I−V) characteristics were analyzed on the basis of the thermionic emission (TE) theory. The experimental barrier height and ideality factor were plotted against (kT) −1 which gives two slopes, one is over the 60–140 K region and the other is over the 160–300 K region presenting a double Gaussian distribution of barrier heights. Two Gaussian distribution analyses of the I−V characteristics of the Re/n-type Si Schottky barrier diodes gave the mean barrier heights of 0.812 and 0.473 eV and standard deviations (σs) of 102 mV and 55 mV, respectively. Therefore, these values of the mean barrier height have been verified with the modified ln(I0/ T2) - q2σo2

A New Method for Investigation of Different Tissues Using Femtosecond Laser Mass Spectrometry

q^{\mathrm {2}}{\sigma _{o}^{2}}

Production and characterization of titanium (Ti), platinum (Pt) and tantalum (Ta) thin films for native DNA biosensors

/2 k2T2 vs (k T)−1 plot which belongs to two temperature sections.

An investigation of localised surface plasmon resonance (LSPR) of Ag nanoparticles produced by pulsed laser deposition (PLD) technique

BACKGROUND Femtosecond laser mass spectrometry (FLMS) has become an important tool for investigation of chemical and biological materials in many areas from medical to industrial. OBJECTIVE In medicine, the morphological examination of tissues is determined by performing pathological investigations under microscope. However, some novel improvements or developments must be performed for much faster diagnosis of the tissue during the operation when patient is under anesthesia. METHODS The information obtained from the tissue under the microscope remains very limited because it cannot reveal characteristics of the whole molecules. For this reason, some novel methods for analysis of tissues are important issues to be achieved. This process can be performed using FLMS much quicker than traditional techniques. The aim of this study is to develop a new procedure for interpretation of mass spectra obtained from different types of muscle tissues, such as lamb, bones, and beef obtained from the butcher. RESULTS The results obtained in this study are believed to open a new window for these kinds of applications for cancer diagnosis on human tissue studies, as a faster analysis technique to give some concrete contributions to pathological examinations. Both, principal component analysis statistical approach and FLMS technique offer a great opportunity to identify the biological materials from mass spectra. In conclusion, this present study interprets a great data from bone, beef, and lamb, which show that we can distinguish these different types of materials using FLMS data and statistical approaches. CONCLUSIONS Eventually, the experimental results obtained from our group studies present that these types of tissues can easily be distinguished using small m/q peaks in the lower region (m/z ≤100 amu) of the mass spectra by courtesy of FLMS.

An experimental investigation of localised surface plasmon resonance (LSPR) for Cu nanoparticles depending as a function of laser pulse number in Pulsed Laser Deposition

The use of the femtosecond (fs) laser pulses for ablation applications have several advantageous and Laser-Induced Forward Transfer (LIFT) is an ablation-driven transfer process. The use of fs laser pulses for LIFT is gaining a great attraction nowadays. The most of the Direct Writing (DW) methods are laser based techniques and the LIFT technique is the one of them. This spectacular technique allows high resolution without lithographic processes. In this study, we have grown Ti, Pt and Ta thin films on the microscope slides by Pulse Laser Deposition (PLD) technique using Nd:YAG laser in the high vacuum condition. As a result, thin films produced in this work is a good candidate to produce native DNA biosensors based on LIFT technique.

Comparison of transition probabilities calculated using different parameters on WBEPM theory for some p‐d and d‐p transitions in excited atomic nitrogen

Noble metal nano-structures such as Ag, Cu, Au are used commonly to increase power conversion efficiency of the solar cell by using their surface plasmons. The plasmonic metal nanoparticles of Ag among others that have strong LSPR in near UV range. They increase photon absorbance via embedding in the active semiconductor of the solar cell. Thin films of Ag are grown in the desired particle size and interparticle distance easily and at low cost by PLD technique. Ag nanoparticle thin films were grown on micro slide glass at 25-36 mJ laser pulse energies under by PLD using ns-Nd:YAG laser. The result of this work have been presented by carrying out UV-VIS and AFM analysis. It was concluded that a laser energy increases, the density and size of Ag-NPs arriving on the substrate increases, and the interparticle distance was decreases. Therefore, LSPR wavelength shifts towards to longer wavelength region.

The theoretical calculation of transition probabilities for some excited p-d transitions in atomic nitrogen

Copper is a low cost metal and its nanoparticles have a unique optical properties such as LSPR. The location of LSPR wavelength can be tuned by controlling nanoparticles sizes and size distributions of nanoparticles, shapes and interparticle distances. This morphological changes are provided by controlling system parameters in PLD. For this work, 48000 and 36000 laser pulses from Nd:YAG laser were applied to produce Cu nanoparticle thin films. These thin films were characterised by performing UV-VIS absorption spectroscopy, Atomic Force Microscopy (AFM) analysis. When the number of laser pulse decreases, the size of Cu nanoparticles and the number of nanoparticles arriving on the substrate are reduced, and LSPR peak of thin films are red shifted depending on the geometrical shapes of the Cu nanoparticles. We have driven a conclusion in this work that LSPR properties of Cu nanoparticles can be tuned by proposed method.Copper is a low cost metal and its nanoparticles have a unique optical properties such as LSPR. The location of LSPR wavelength can be tuned by controlling nanoparticles sizes and size distributions of nanoparticles, shapes and interparticle distances. This morphological changes are provided by controlling system parameters in PLD. For this work, 48000 and 36000 laser pulses from Nd:YAG laser were applied to produce Cu nanoparticle thin films. These thin films were characterised by performing UV-VIS absorption spectroscopy, Atomic Force Microscopy (AFM) analysis. When the number of laser pulse decreases, the size of Cu nanoparticles and the number of nanoparticles arriving on the substrate are reduced, and LSPR peak of thin films are red shifted depending on the geometrical shapes of the Cu nanoparticles. We have driven a conclusion in this work that LSPR properties of Cu nanoparticles can be tuned by proposed method.