Ultrafast Laser Ablation, Intrinsic Threshold, and Nanopatterning of Monolayer Molybdenum Disulfide

Laser direct writing is an attractive method for patterning 2D materials without contamination. Literature shows that the femtosecond ablation threshold of graphene across substrates varies by an order of magnitude. Some attribute it to the thermal coupling to the substrates, but it remains by and large an open question. For the first time the effect of substrates on femtosecond ablation of 2D materials is studied using MoS$_{2}$ as an example. We show unambiguously that femtosecond ablation of MoS$_{2}$ is an adiabatic process with negligible heat transfer to the substrates. The observed threshold variation is due to the etalon effect which was not identified before for the laser ablation of 2D materials. Subsequently, an intrinsic ablation threshold is proposed as a true threshold parameter for 2D materials. Additionally, we demonstrate for the first time femtosecond laser patterning of monolayer MoS$_{2}$ with sub-micron resolution and mm/s speed. Moreover, engineered substrates are shown to enhance the ablation efficiency, enabling patterning with low-power femtosecond oscillators. Finally, a zero-thickness approximation is introduced to predict the field enhancement with simple analytical expressions. Our work clarifies the role of substrates on ablation and firmly establishes femtosecond laser ablation as a viable route to pattern 2D materials

Age and Gender Differences in Urinary Levels of Eleven Phthalate Metabolites in General Taiwanese Population after a DEHP Episode.

In 2011, the Taiwan FDA disclosed illegal di(2-ethylhexyl phthalate) (DEHP) and dibutyl phthalate (DBP) use in beverage and nutrition supplements. We aim to determine phthalate exposure and other relevant factors in a sample of the general Taiwanese population in order to evaluate actual phthalate exposure levels after this disclosure of DEHP use.We selected subjects aged 7 years old and older in 2013 from the general Taiwanese population. First morning urine samples from each participant were collected to analyze 11 phthalate metabolites representing 7 parent phthalates using on-line liquid chromatography/ tandem mass spectrometry. An interview questionnaire was applied to obtain participant demographic characteristics, lifestyle, and other relevant factors.The median levels of metabolites of DEHP, including mono-ethylhexyl phthalate (MEHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), DBP (DnBP and DiBP), including mono-n-butyl phthalate (MnBP) and mono-iso-butyl phthalate (MiBP), and mono-ethyl phthalate (MEP) in urine samples of 290 adults/ 97 minors (<18 years) were 7.9/ 6.1, 12.6/ 17.8, 22.0/ 25.8, 25.4/ 30.8, 18.1/ 23.6, 9.4/ 13.6 and 14.5/ 12.4 μg/g creatinine, respectively. Women (≧18 years) were exposed to significantly higher levels of MEHHP (P=0.011), MECPP (P=0.01), MnBP (P=0.001) and MEP (P<0.001) than men (≧18 years), whereas no gender difference was observed in minors. We found significant higher level of MEP (creatinine-unadjusted) in subject aged between 18 to 40 years old (P<0.001), especially for women. Exposure levels of MEOHP (P<0.001), MECPP (P=0.002) and MnBP (P=0.044) in minors were significantly higher than those of adults. High frequency usage of food preservation film and bags, and personal care products are potential sources of phthalates exposure in general Taiwanese.Our findings indicated that DEHP and DBP exposure in a sample of the general Taiwanese population varied by age and gender, possibly affected by different lifestyles, and continuing bio-monitoring surveillance is warranted

Early Phthalates Exposure in Pregnant Women Is Associated with Alteration of Thyroid Hormones

<div><p>Introduction</p><p>Previous studies revealed that phthalate exposure could alter thyroid hormones during the last trimester of pregnancy. However, thyroid hormones are crucial for fetal development during the first trimester. We aimed to clarify the effect of phthalate exposure on thyroid hormones during early pregnancy.</p><p>Method</p><p>We recruited 97 pregnant women who were offered an amniocentesis during the early trimester from an obstetrics clinic in southern Taiwan from 2013 to 2014. After signing an informed consent form, we collected amniotic fluid and urine samples from pregnant women to analyze 11 metabolites, including mono-ethyl phthalate (MEP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-(2-ethylhexyl) phthalate (MEHP), mono-butyl phthalate (MnBP), of 9 phthalates using liquid chromatography/ tandem mass spectrometry. We collected blood samples from each subject to analyze serum thyroid hormones including thyroxine (T₄), free T₄, and thyroid-binding globulin (TBG).</p><p>Results</p><p>Three phthalate metabolites were discovered to be >80% in the urine samples of the pregnant women: MEP (88%), MnBP (81%) and MECPP (86%). Median MnBP and MECPP levels in pregnant Taiwanese women were 21.5 and 17.6 μg/g-creatinine, respectively, that decreased after the 2011 Taiwan DEHP scandal. Results of principal component analysis suggested two major sources (DEHP and other phthalates) of phthalates exposure in pregnant women. After adjusting for age, gestational age, TBG, urinary creatinine, and other phthalate metabolites, we found a significantly negative association between urinary MnBP levels and serum T₄ (β = –5.41; p-value = 0.012; n = 97) in pregnant women using Bonferroni correction.</p><p>Conclusion</p><p>We observed a potential change in the thyroid hormones of pregnant women during early pregnancy after DnBP exposure. Additional study is necessitated to clarify these associations.</p></div

Demographic Characteristics of Participating Pregnant Taiwanese Women (N = 97).

<p>Demographic Characteristics of Participating Pregnant Taiwanese Women (N = 97).</p

Comparison of urinary levels of seven phthalate metabolites in a general population sample of Taiwanese (≧7 years), Americans (>6 years) and Canadians (18–49 years).

<p>Comparison of urinary levels of seven phthalate metabolites in a general population sample of Taiwanese (≧7 years), Americans (>6 years) and Canadians (18–49 years).</p

Pearson correlation between thyroid hormone, age, duration of gestation, time to pregnancy and urinary phthalate metabolite levels (ng/ mL, N = 97)^a.

<p>Pearson correlation between thyroid hormone, age, duration of gestation, time to pregnancy and urinary phthalate metabolite levels (ng/ mL, N = 97)<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159398#t004fn001" target="_blank">^a</a>.</p

Distribution of 11 phthalate metabolites in a sample of the general Taiwanese population (N = 387) ≥7 years of age.

<p>Distribution of 11 phthalate metabolites in a sample of the general Taiwanese population (N = 387) ≥7 years of age.</p

Comparison of urinary phthalate metabolites (ng/mL) at the first trimester in pregnant women in Taiwan, Unite States, Canada and Puerto Rico.

<p>TBC: Tainan Birth Cohort; TIDES: The Infant Development and the Environment Study; MIREC: Maternal-Infant Research on Environmental Chemicals; PROTECT: Puerto Rico Testsite for Exploring Contamination Threats.</p

Scatter plot of correlation between serum thyroxin and urinary MnBP in pregnant women at first trimester (N = 97).

<p>Scatter plot of correlation between serum thyroxin and urinary MnBP in pregnant women at first trimester (N = 97).</p

Distribution of serum thyroid hormones and urinary creatinine in participants (N = 97) at the first trimester.

<p>Distribution of serum thyroid hormones and urinary creatinine in participants (N = 97) at the first trimester.</p