Time domain terahertz spectroscopy: construction of the setup and application in analysis of active pharmaceutical ingredients

Aytekin, Yusuf Samet
The purpose of this thesis is to build a homemade Terahertz (THz) Time Domain Spectrometer and analysis of Active Pharmaceutical Ingredients (API) by using the built THz-TDS spectrometer. Several configurations of THz-TDS system were setup and tested in order to optimise experimental parameters. These set-ups can be grouped into two; antenna-antenna and antenna-crystal. In antenna-antenna systems, photoconductive antenna (PCA)and interdigital photoconductive antenna (iPCA) were employed and both were tried for generation and detection of THz field. None of the two set-ups resulted in a good signal-to-noise ratio (SNR) or dynamical range (DR) both in time domain and frequency domain. In antenna-crystal systems, both PCA and iPCA were employed for terahertz generation and 500 µm ZnTe crystal was used for electro-optic sampling. In this case, iPCA-crystal combination gave the best SNR and larger dynamical range. Once the generation and detection types were determined, optimisation studies were carried out to measure optical properties of APIs. A modelocked oscillator Ti:Sapphire laser with central wavelength of 800 nm, repetition rate of 80 MHz, pulse duration of 80 fs and output power of ~550 mW was used as the laser source to generate and detect THz radiation. The final system has 3 THz bandwitdh and > 105 SNR. Afterwards, several APIs of common drugs were analysed by using both the optimised homemade THz-TDS setup and FT-THz system. The results have shown that each API had a characteristic THz spectrum, that can be used for the identification and characterisation of API.


Gelgeç, Melis; Altan, Hakan; Department of Physics (2022-8-25)
In this thesis, a Terahertz Attenuated Total Reflection Time Domain Spectroscopy (THz ATR-TDS) system was constructed to measure biological media. The constructed system driven by a Yb:doped mode-locked fiber laser had a limited bandwidth of about 0.3 THz. This bandwidth limited the analysis of various samples in the frequency domain. To overcome this limitation a method was developed so that the samples can be analyzed in the time-domain. Oral soft tissue samples collected were used in order to demonstrate...
Fabrication and characterization of photocrosslinked phase change materials by using conventional and terahertz spectroscopy techniques
Aytan, Emre; Aytekin, Yusuf Samet; Esentürk, Okan; KAHRAMAN, MEMET VEZİR (2019-12-01)
A series of novel photocrosslinked shape-stabilized phase change materials (PCMs) based on tetradecanol and lauric acid have been prepared by UV technique for the purpose of thermal energy storage applications. Both lauric acid and tetradecanol were reacted with glycidyl methacrylate to form acrylated structures for covalently integrate into polyurethane (PU) based UV matrix to prevent leakage problem. The heating process phase change enthalpy is measured between 9 and 77 J/g, and the freezing process phase...
Experimental investigation of nanofluids using terahertz time domain spectroscopy (THz TDS)
Koral, Can; Okutucu Özyurt, Hanife Tuba; Altan, Hakan; Department of Micro and Nanotechnology (2012)
In this study, suspensions of metallic nanoparticles in base fluids, nanofluids, are investigated by using terahertz time domain spectroscopy (THz-TDS). Nanofluids are used as the working fluid in a variety of applications especially for the purpose of heat transfer enhancement. Polar fluids are being used as the base in nanofluids for their tendency to stop aggregation and sedimentation. Polar fluids highly absorb THz signal. In order to select the best possible host, various polar liquids have been invest...
Terahertz Transmission Through Patterened Vanadium Oxide Thin Films on Dielectric Substrates
AKKAYA, MAHİNUR; Demirhan, Y.; Yuce, H.; Aygun, G.; Ozyuzer, L.; SABAH, CUMALİ; Altan, Hakan (SCITEPRESS, AV D MANUELL, 27A 2 ESQ, SETUBAL, 2910-595, PORTUGAL; 2017-03-01)
Patterned and unpatterned films of vanadium oxide grown on dielectric substrates such as fused silica and sapphire were grown and analysed by varying the temperature using terahertz time domain spectroscopy. After investigating the critical transition temperature near 340K, a well-known cross-shaped pattern was studied to observe any resonances upon transmission. Due to the poor conductivity of the films the frequency selective nature of the structure was not observed, however an etalon effect could be seen...
Construction of terahertz spectrometers and their use in characterization of conductivities and modulation behaviors of graphene layers /
Kaya, Emine; Esentürk, Okan; Department of Chemistry (2017)
Aim of this thesis was to construct two new terahertz spectrometers, THz Time Domain Spectroscopy (THz-TDS) and Time Resolved THz Spectroscopy (TRTS) for characterization of the static and dynamic properties of novel materials. After successful construction and signal optimization, system characterizations of both systems were completed with well-known samples. Possible use of ionic liquid doped graphene devices on PVC and PE substrates were characterized by THz-TDS. Devices operated at low voltages and pro...
Citation Formats
Y. S. Aytekin, “Time domain terahertz spectroscopy: construction of the setup and application in analysis of active pharmaceutical ingredients,” M.S. - Master of Science, Middle East Technical University, 2016.