Ultralow bandgap molecular semiconductors for ambient-stable and solution-processable ambipolar organic field-effect transistors and inverters

Ozdemir, Resul,Choi, Donghee,Ozdemir, Mehmet,Kwon, Guhyun,Kim, Hyekyoung,Sen, Unal,Kim, Choongik,Usta, Hakan The Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.9

<P>The design and development of novel ambipolar semiconductors is very crucial to advance various optoelectronic technologies including organic complementary (CMOS) integrated circuits. Although numerous high-performance ambipolar polymers have been realized to date, small molecules have been unable to provide high ambipolar performance in combination with ambient-stability and solution-processibility. In this study, by implementing highly π-electron deficient, ladder-typeIFDK/IFDMacceptor cores with bithiophene donor units in D-A-D π-architectures, two novel small molecules,2OD-TTIFDKand2OD-TTIFDM, were designed, synthesized and characterized in order to achieve ultralow band-gap (1.21-1.65 eV) semiconductors with sufficiently balanced molecular energetics for ambipolarity. The HOMO/LUMO energies of the new semiconductors are found to be −5.47/−3.61 and −5.49/−4.23 eV, respectively. Bottom-gate/top-contact OFETs fabricated<I>via</I>solution-shearing of2OD-TTIFDMyield perfectly ambient stable ambipolar devices with reasonably balanced electron and hole mobilities of 0.13 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP>and 0.01 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP>, respectively with<I>I</I>on/<I>I</I>offratios of ∼10<SUP>3</SUP>-10<SUP>4</SUP>, and2OD-TTIFDK-based OFETs exhibit ambipolarity under vacuum with highly balanced (<I>μ</I>e/<I>μ</I>h∼ 2) electron and hole mobilities of 0.02 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP>and 0.01 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP>, respectively with<I>I</I>on/<I>I</I>offratios of ∼10<SUP>5</SUP>-10<SUP>6</SUP>. Furthermore, complementary-like inverter circuits were demonstrated with the current ambipolar semiconductors resulting in high voltage gains of up to 80. Our findings clearly indicate that ambient-stability of ambipolar semiconductors is a function of molecular orbital energetics without being directly related to a bulk π-backbone structure. To the best of our knowledge, considering the processing, charge-transport and inverter characteristics, the current semiconductors stand out among the best performing ambipolar small molecules in the OFET and CMOS-like circuit literature. Our results provide an efficient approach in designing ultralow band-gap ambipolar small molecules with good solution-processibility and ambient-stability for various optoelectronic technologies, including CMOS-like integrated circuits.</P>

Flexural Behavior of Laminated Wood Beams Strengthened with Novel Hybrid Composite Systems: An Experimental Study

( Mehmet Faruk Ozdemir ),( Muslum Murat Maras ),( Hasan Basri Yurtseven ) 한국목재공학회 2023 목재공학 Vol.51 No.6

Wooden structures are widely used, particularly in earthquake zones, owing to their light weight, ease of application, and resistance to the external environment. In this study, we aimed to improve the mechanical properties of laminated timber beams using novel hybrid systems [carbon-fiber-reinforced polymer (CFRP) and wire rope]. Within the scope of this study, it is expected that using wood, which is an environmentally friendly and sustainable building element, will be more economical and safe than the reinforced concrete and steel elements currently used to pass through wide openings. The structural behavior of the hybrid-reinforced laminated timber beams was determined under the loading system. The experimental findings showed that the highest increase in the values of laminated beams reinforced with steel ropes was obtained with the 2N reinforcement, with a maximum load of 38 kN and a displacement of 137 mm. Thus, a load increase of 168% and displacement increase of 275% compared with the reference sample were obtained. Compared with the reference sample, a load increase of 92% and a displacement increase of 14% were obtained. Carbon fabrics placed between the layers with fiber-reinforced polymer (FRP) prevented crack development and provided significant interlayer connections. Consequently, the fabrics placed between the laminated wooden beams with the innovative reinforcement system will not disrupt the aesthetics or reduce the effect of earthquake forces, and significant reductions can be achieved in these sections.

Solution-Processable BODIPY-Based Small Molecules for Semiconducting Microfibers in Organic Thin-Film Transistors

Ozdemir, Mehmet,Choi, Donghee,Kwon, Guhyun,Zorlu, Yunus,Cosut, Bunyemin,Kim, Hyekyoung,Facchetti, Antonio,Kim, Choongik,Usta, Hakan American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.22

<P>Electron-deficient pi-conjugated small molecules can function as electron-transporting semiconductors in various optoelectronic applications. Despite their unique structural, optical, and electronic properties, the development of BODIPY-based organic semiconductors has lagged behind that of other pi-deficient units. Here, we report the design and synthesis of two novel solution-proccessable BODIPY-based small molecules (BDY-3T-BDY and BDY-4T-BDY) for organic thin-film transistors (OTFTs). The new semiconductors were fully characterized by H-1/C-13 NMR, mass spectrometry, cyclic voltammetry, UV-vis spectroscopy, photoluminescence, differential scanning calorimetry, and thermogravimetric analysis. The single-crystal X-ray diffraction (XRD) characterization of a key intermediate reveals crucial structural properties. Solution-sheared top-contact/bottom-gate OTFTs exhibited electron mobilities up to 0.01 cm(2)/V center dot s and current on/off ratios of >10(8). Film microstructural and morphological characterizations indicate the formation of relatively long (similar to 0.1 mm) and micrometer-sized (1-2 mu m) crystalline fibers for BDY-4T-BDY-based films along the shearing direction. Fiber-alignment-induced charge-transport anisotropy (mu?/mu approximate to 10) was observed, and higher mobilities were achieved when the microfibers were aligned along the conduction channel, which allows for efficient long-range charge-transport between source and drain electrodes. These OTFT performances are the highest reported to date for a BODIPY-based molecular semiconductor, and demonstrate that BODIPY is a promising building block for enabling solution-processed, electron-transporting semiconductor films.</P>

Recurrence Risk and Prognostic Parameters in Stage I Rectal Cancers

Cihan, Sener,Kucukoner, Mehmet,Ozdemir, Nuriye,Dane, Faysal,Sendur, Mehmet Ali Nahit,Yazilitas, Dogan,Urakci, Zuhat,Durnali, Ayse,Yuksel, Sinemis,Aksoy, Sercan,Colak, Dilsen,Seker, Mehmet Metin,Taskoy Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.13

Background: The standard therapy for stage I rectum cancer is surgical resection. Currently, there is no strong evidence to suggest that any type of adjuvant therapy is beneficial. The risks of local relapse and distant metastasis are higher in rectal tumors. Therefore, while there is no clearly defined absolute indication for adjuvant therapy in lymph node negative colon cancers, rectum tumors that are T3N0 and higher require adjuvant treatment. Due to the more aggressive nature of rectal cancers, we explored the clinical and pathologic factors that could predict the risk of relapse in Stage I (T1-T2) disease and whether there was any progression-free survival benefit to adjuvant therapy. Materials and Methods: This multicenter study was carried out by the Anatolian Society of Medical Oncology. A total of 178 patients with rectal cancers who underwent curative surgery between January 1994 and August 2012 in 13 centers were included in the study. Patient demographics, including survival data and tumor characteristics were obtained from medical charts. Results: The median age was 58 years (range 26-85 years). Most tumors were well or moderately differentiated. For adjuvant treatment, 13 patients (7.3%) received radiotherapy alone, 12 patients (6.7%) received chemotherapy alone and 15 patients (8.4%) were given chemoradiotherapy. Median follow up was 29 months (3-225 months). Some 42 patients (23.6%) had relapse during follow up; 30 with local recurrence (71.4%) whereas 12 (28.6%) were distant metastases. Among the patients, 5-year DFS was 64% and OS was 82%. Mucinous histology and receiving adjuvant therapy were found to have statistically insignificant correlations with relapse and survival. Conclusions: In our retrospective analysis, approximately one quarter of patients exhibited either local or systemic relapse. The rates of relapse were slightly higher in the patients who had no adjuvant therapy. There may thus be a role for adjuvant therapy in high-risk stage I rectal tumors.

Pretreatment Neutrophil/Lymphocyte Ratio as a Prognostic Aid in Colorectal Cancer

Ozdemir, Yavuz,Akin, Mehmet Levhi,Sucullu, Ilker,Balta, Ahmet Ziya,Yucel, Ergun Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.6

Background: Colorectal cancers(CRC) are the third most common cancer in the western world, with surgery preferred for management of non-metastatic disease and post surgical treatment usually arranged according to the TNM staging system. However, there is still prognostic variation between patients who have the same stage. It is increasingly recognized that variations within disease course and clinical outcome in colorectal cancer patients are influenced by not only oncological characteristics of the tumor itself but also host response factors. Recent studies have shown correlation between the inflammatory response and clinical outcomes in various cancers. The neutrophil/lymphocyte ratio (NLR) has been described as a marker for immune response to various stimuli including cancer. Material-Methods: Two hundred eighty-one CRC patients were included in our retrospective analysis, separated into two groups according to a cut-off value for the NLR. Patient data including age, gender, vertical penetration, anatomic location, and differentiation of the tumor, TNM stage, survival rate, and disease-free survival were analyzed for correlations with the NLR. Results: Using ROC curve analysis, we determined a cut-off value of 2.2 for NLR to be best to discriminate between patient survival in the whole group. In univariate analysis, high pretreatment NLR (p=0.001, 95%CI 1.483-4.846), pathologic nodal stage (p<0.001, 95%CI 1.082-3.289) and advanced pathologic TNM stage (p<0.001, 95%CI 1.462-4.213) were predictive of shorter survival. In multivariate analysis, advanced pathologic TNM stage (p=0.001, 95%CI 1.303-26.542) and high pretreatment NLR (p=0.005, 95%CI 1.713-6.378) remained independently associated with poor survival. Conclusions: High pre-treatment NLR is a significant independent predictor of shorter survival in patients with colorectal cancer. This parameter is a simple, easily accessible laboratory value for identifying patients with poorer prognosis.

Efficacy and Safety of First Line Vincristine with Doxorubicin, Bleomycin and Dacarbazine (ABOD) for Hodgkin's Lymphoma: a Single Institute Experience

Ozdemir, Nuriye,Dogan, Mutlu,Sendur, Mehmet Ali Nahit,Yazici, Ozan,Abali, Huseyin,Yazilitas, Dogan,Akinci, Muhammed Bulent,Aksoy, Sercan,Zengi, Nurullah Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.20

Background: ABVD (doxorubicin, bleomycin, vinblastine (Vb) and dacarbazine) is the standard regimen in Hodgkin's lymphoma (HL).Vincristine (O) is a mitotic spindle agent like Vb. We aimed to evaluate the efficacy and safety of O as a part of ABOD in HL. Materials and Methods: Patients who had ABOD were enrolled. Stage I-II HL were evaluated for unfavorable risk factors according to NCCN. National Cancer Institute Common Toxicity Criteria was used for toxicity. Results: Seventy-nine HL patients in our center between 2003 and 2007 were evaluated retrospectively. Median follow-up was 54 months. Most of the patients were male in their third decade. Median ABOD cycles were 6 (2-8). Primary refractory disease rate was 17.7% whereas it was 5.1% for early relapse and 5.1% for late relapse disease. Response rates were as 82.3% for complete response, 11.4% for partial response, 5.1% for stable disease and 1.3% for progressive disease. Half of relapsed patients had autologous stem cell transplantation. Estimated 5-year failure-free survival was 71% and significantly longer in early stage patients without risk factors, bulky disease or radiotherapy (RT) (p=0.05, p<0.0001, p=0.02; respectively). Estimated 5-year overall survival was 74% and significantly longer in those who had no RT (p=0.001). Dose modification rate was 5.1% and chemotherapy delay rate was 19%. There were no toxicity-related deaths. Conclusions: ABOD seems to be effective with managable toxicity in HL, even in those with poor prognostic factors.

Oral Etoposide for Platinum-Resistant and Recurrent Epithelial Ovarian Cancer: a Study by the Anatolian Society of Medical Oncology

Kucukoner, Mehmet,Isikdogan, Abdurrahman,Yaman, Sebnem,Gumusay, Ozge,Unal, Olcun,Ulas, Arife,Elkiran, Emir T.,Kaplan, Muhammed A.,Ozdemir, Nuriye,Inal, Ali,Urakci, Zuhat,Buyukberber, Suleyman Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.8

Background: The aim of this study was to evaluate the efficacy and toxicity of long-term, low-dose oral etoposide as an advanced treatment option in patients with platinum resistant epithelial ovarian cancer. Materials and Methods: For the purposes of this study, 51 patients with histologically-confirmed, recurrent or metastatic platinum-resistant epithelial ovarian cancer (EOC) treated at six different centers between January 2006 and January 2011 were retrospectively evaluated. Patients were treated with oral etoposide (50 mg/day for a cycle of 14 days, repeated every 21 days). Results: Among the 51 platinum-resistant patients, 17.6% demonstrated a partial response and 25.5% a stable response. The median progression-free survival (PFS) was 3.9 months (95% CI, 2.1-5.7), while the median overall survival was 16.4 months (11.8.20.9). No significant relationship was observed between the pre-treatment CA 125 levels, post-treatment CA-125 levels and the treatment response rates (p=0.21). Among the 51 patients who were evaluated in terms of toxicity, grade 1 or 4 hematologic toxicity was observed in 19 (37.3%); and grade 1-4 gastrointestinal toxicity occurred in 15 patients (29.4%). Conclusions: Chronic low-dose oral etoposide treatment is generally effective and well-tolerated in platinum-resistant ovarian cancer patients.

Does Zoledronic Acid Have Additive Effect on Suppression of Plasma Estrogen Levels ?

Sendur, Mehmet Ali Nahit,Aksoy, Sercan,Ozdemir, Nuriye Yildirim,Akinci, Muhammed Bulent,Zengin, Nurullah,Altundag, Kadri Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.1

What is the Mechanism of Progression with Trastuzumab Treatment - Escape or Resistance?

Sendur, Mehmet Ali Nahit,Aksoy, Sercan,Ozdemir, Nuriye Yildirim,Zengin, Nurullah,Altundag, Kadri Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.11

Human epidermal growth factor receptor (HER) 2 overexpression, observed in 20-25 percent of invasive breast cancers, is well known to be associated with a more aggressive phenotype and poor prognosis, with resistance to certain chemotherapeutic agents. The majority of patients with metastatic breast cancer who initially respond to trastuzumab, demonstrate disease progression within 1 year of treatment initiation. Furthermore, lack of response in some patients and relapse during the course of therapy, continue to challenge researchers and clinicians. A better understanding of the fundamental mechanisms of trastuzumab action is required so that new therapies directed at HER2 can be developed. We present here findings for mechanisms, both of Trastuzumab action and clinical resistance or escape.

Treatment and Outcomes of Ewing Sarcoma in Turkish Adults: A Single Centre Experience

Seker, Mehmet Metin,Kos, Tugba,Ozdemir, Nuriye,Seker, Ayse,Aksoy, Sercan,Uncu, Dogan,Zengin, Nurullah Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.1

Background: Ewing sarcoma is a small round cell tumor arising from soft tissue and bone that predominantly affects children and adolescents. The most unfavorable prognostic factor is the presence of distant metastasis at the time of diagnosis. Materials and Methods: The records of 26 Ewing sarcoma patients (14 male, 12 female) were re-evaluated retrospectively. Results: The median age was 26.5 (19-42) years. Eight patients (31%) showed a primary tumor in their extremities, 8 (31%) in the thorax, 4 (15%) at the vertebra, 4 (15%) in the head and neck, and 2 (8%) in the abdomen. Five patients (19%) had distant metastasis at diagnosis. The median progression-free survival was 72 months and 10 months in localized and metastatic disease, respectively (p=0.005). The overall survival rate was 19 months in metastatic disease, and the 5-year overall survival rate was 64% in localized disease (p=0.006). Patients who had localized disease in the extremities and were under age 30 had a favorable prognosis. Conclusions: Although Ewing sarcoma is a tumor affecting children and adolescents, it may be seen in adults, where the prognosis is generally worse. Although it is a highly malignant tumor, it is possible to achieve improved survival with combined modality treatments.