Exploring the Hubble tension problem with phantom dark energy

August 09, 2023

【Provided by Associate Professor Wo-Lung Lee and his team】 Recently, the observed equation of state for dark energy appears to favor values below −1. The tendency implies that the nature of dark energy may be quite different from that of the cosmological constant. In view of this, the introduction of the phantom energy seems inevitable. By employing observational constraints from supernovae and from the acoustic scale in which the accuracy of the data has become extraordinary, the research team applied a phenomenological scenario to be acquainted with the evolution of our universe. The demonstration of the constrained unfolding of the phantom energy shows that the model has high consistency with the current observation, suggesting that if it is phantom dark energy that is causing the accelerating expansion of the universe instead of the cosmological constant, then the Hubble constant may be different from the recent observations, and the “Hubble tension” problem may not be as severe as expected.    In the current standard model of cosmology, the dominant component driving the accelerated expansion of the universe is the so-called cosmological constant. However, the Hubble constant derived from the analysis of the primordial acoustic oscillations in the cosmic microwave background within the standard model exhibits a significant discrepancy with the rate of cosmic expansion inferred from observations of recent supernovae events. This "Hubble tension" problem seriously troubles the entire scientific community. Inspired by the trend of observed equation of state for dark energy below -1, our research team constructed a phenomenological model of dynamic dark energy The analysis results from the research team indicate that if phantom dark energy is used instead of the cosmological constant in the standard model, the so-called "Hubble tension" problem is not as severe and may even be resolved. This suggests that researchers must carefully reconsider the reasons behind the recent cosmic accelerated expansion phenomenon, and even consider modifying the standard cosmological model further!     Figure 1: Correspondence between dark energy state equation values and the Hubble constant, and the distribution of errors in the primordial acoustic oscillation scale.   Source: Teng, Y. P., Lee, W., & Ng, K. W. (2021). Constraining the dark-energy equation of state with cosmological data. Physical Review D, 104(8),[A24].https://doi.org/10.1103/PhysRevD.104.083519 

A Revolutionary Discovery for Solar Cells

August 09, 2023

(Provided by Distinguished Professor Yann-Wen Lan and his research team from the Department of Physics) In the pursuit of cleaner energy, solar cells are expected to be widely applied in various fields; however, current solar cells are limited in their development due to the low conversion efficiency of light to electricity. To enhance the material's absorption of light, the research team altered the characteristics of light by utilizing twisted light. Photons of twisted light carry an orbital angular momentum. Additional orbital angular momentum is expected to induce more carrier transitions within the material, thereby increasing the material's light absorption and its photogenerated carrier concentration, elevating its potential for application in solar cells. The highlight of this experiment lies in using twisted light to enhance the light absorption of novel 2D material molybdenum disulfide. As the orbital angular momentum of light increments, the concentration of photo-induced carriers rises as well. Consequently, the larger photovoltaic effect in solar cells is enhanced. Based on the results of this experiment, twisted light has shown its potential to become a new approach to enhancing the efficiency of solar cells.   With the increasing desire for green energy, solar cells are highly anticipated; however, the low conversion efficiency has led to a bottleneck in their application. Therefore, improving the conversion efficiency of solar cells has become a very important research topic. Professor Yann-Wen Lan and Professor Ting-Hua Lu from the Department of Physics at National Taiwan Normal University collaborated with their student, Dr Kristan Bryan Simbulan, to conduct related research, the findings of which revealed that light with orbital angular momentum (OAM) can enhance the power generation efficiency of solar cells using molybdenum disulfide as material. This opens up endless possibilities for the future of the solar cell industry. The solar cell component in this study is composed of a transition metal dichalcogenide, specifically molybdenum disulfide (MoS2), which has a thickness at the atomic level. MoS2 is a stable and flexible two-dimensional material that produces a unique optical response. This, and its potential to be perfectly stacked with other 2D materials, makes it a rising star in the semiconductor materials field. The fabrication process involves depositing MoS2 onto a silicon substrate through chemical vapor deposition (CVD), then defining the MoS2 channels using Argon plasma etching, and finally depositing the Ti/Au source and drain electrodes to complete the device. The CVD-grown MoS2 material in the study has a nonuniform defect distribution, leading to n and n+ regions within the material and forming p-n junctions. The simple fabrication process and the potential for large-scale production through chemical vapor deposition lay the groundwork for future industrial mass production possibilities. In comparison with traditional laser lights, the wavefront of twisted light is not flat but instead helical. By adjusting the spatial distribution of the light wavefront through a spatial light modulator (SLM), light can possess arbitrary orbital angular momentum. Additional OAM has been proven to interact with materials and was demonstrated in previous studies to have induced forbidden transitions in atoms and GaAs semiconductors. The OAM in twisted light could thus be used as a new degree of freedom to enhance the material's light absorption, thereby increasing photo-induced carrier concentration. In the case of photovoltaic cells, increased photogenerated carrier concentration can lead to improved photovoltaic properties, such as short-circuit current (ISC) and open-circuit voltage (VOC). Experimental data indicated that with the increase in the OAM of the laser light, higher ISC and VOC have both been measured, demonstrating the potential of enhancing the photovoltaic effect through twisted light. Professor Yann-Wen Lan, with his expertise in 2D materials, nanoelectronics, and device processes, collaborated with Professor Ting-Hua Lu, who specializes in laser physics and optical angular momentum techniques. With support from National Taiwan Normal University and the National Science and Technology Council (NSTC), their collaboration spanned over two years, covering the preparation of components, setting up light sources, and ultimately collecting and analyzing measurement data to complete the research project. The discovery of enhancing solar cell efficiency using twisted light represents a ground-breaking advancement, and in August 2021, their research was published in the prestigious international journal, ACS NANO, paving the way for new avenues in the future solar energy industry.  Professor Lan Yann-Wen explained that the current focus of the solar cell industry largely revolves around material development, attempting to absorb a broader range of wavelengths. If this technology could be combined with the aforementioned technique in the future, revolutionary discoveries are only a matter of time. In future research, the team will stack different two-dimensional materials and utilize the degrees of freedom of light on such heterogeneous structures to explore the interaction between light and matter. This has the potential to bring about breakthrough developments in industries such as semiconductors and optoelectronics.   Source:  Simbulan, K. B., Feng, Y. J., Chang, W. H., Lu, C. I., Lu, T. H., & Lan, Y. W. (2021). Twisted Light-Enhanced Photovoltaic Effect. ACS Nano, 15(9), 14822-14829. https://doi.org/10.1021/acsnano.1c04902 

An arduous journey back home for Formosan Landlocked Salmon

May 10, 2022

(This report is provided by Dr. Lee’s research team in the Department of Geography) The Formosan landlocked salmon is a critically endangered species also known as the Taiwanese ‘national treasure fish.’ In recent years, the fish was stocked into Rahaw Creek (upper Yusheng Creek, Yilan), where a sustainable group had been successfully rehabilitated. Lately, however, frequent stream fragmentation events in Yusheng Creek have prevented the fish from expanding their habitat, killing many as a result. To understand the reasons for the fragmentation and to improve rehabilitation, the research team installed six monitoring wells across a 500-meter fragmented reach to record temperatures and groundwater levels, which allowed them to understand surface water-groundwater interactions over different periods. The findings showed that compared to the perennial ones, the fragmented reach is of significantly higher streambed vertical hydraulic conductivity, causing the water to infiltrate the streambed at higher speeds. The findings also indicated that the vertical hydraulic conductivity was influenced by discharge, rainfall changes and the remains of dead diatoms. Most fragmentation studies focus on streams in semi-arid climates. This paper not only demonstrates the uniqueness of how mountain stream discharge in humid subtropical climates is affected by hydrological conditions and bioactivities, but also sheds light on the complexity of surface water-groundwater interactions by examining temporal variations in hydraulic conductivity.   There is no doubt that fragmentation of a stream would impact its ecosystem, as no fish would be able to survive in a river without stream flow. The Taiwanese “national treasure” Formosan landlocked salmon is a cold-water fish native to Chichiwan Creek. Once at the brink of extinction, the fish population in mainstem Chichiwan Creek has since been stabilised thanks to the joint efforts of the Shei-Pa National Park Administration along with many other professionals. The salmon was stocked into its historical habitats, with Rahaw Creek (upper Yusheng Creek) being the most successful one as the fish were shown to expand downstream towards Yusheng Creek. However, the watercourse of Yusheng Creek was drastically altered and began showing frequent fragmentations in the wake of a flash flood caused by a typhoon in 2012. Instead of flowing along the surface, much of the river water infiltrated the streambed and became groundwater. The dried-up watercourse limited the salmon’s expansion of habitat to the point that their way back upstream became cut off, leaving them stranded downstream in an unsuitable habitat. In the hope of improving rehabilitation under the support of the “Shei-Pa National Park Project,” a team of experts from the Department of Geography at NTNU, Institute of Earth Sciences at NTOU, Department of Bioenvironmental Systems Engineering at NTU, and the Wuling Workstation of Shei-Pa National Park Administration set out to understand the reasons for the fragmentations by installing 6 monitoring wells across a 500-metre reach in the fragmented reaches to record temperatures and groundwater levels. This allowed them to gain insights into surface water-groundwater interactions over different time periods. The findings were published in the Journal of Hydrology (https://doi.org/10.1016/j.jhydrol.2020.124665). Since it is not possible to directly measure surface water-groundwater flow, the research team utilised ‘heat’ as a natural tracer. By monitoring the thermal activity of the cross-sectioned streambed through the wells, and comparing the water level of the stream against that of the wells, the researchers were able to see how the water was moving within the streambed. When the water level of the stream is higher than that of the wells, the water begins to infiltrate the streambed. The temperature of the streambed would thus show how much heat is passing downwards. Therefore, reaches with stronger infiltration (high water levels in the stream compared to the wells) would show similar thermal changes between ground and surface water. Conversely, reaches with weaker infiltration would show dissimilar temperature records in the streambed compared to that of the surface. By examining the thermal cross sections of the streambed, the vertical speed of water in the streambed, or hydraulic conductivity, could thus be learned. The findings showed that compared to the perennial ones, the fragmented reaches have significantly higher streambed hydraulic conductivity, meaning that the water was infiltrating the streambed at higher speeds. It is typical that hydraulic conductivity in perennial reaches should be doubled after rainfall as higher volumes of discharge remove sedimentation clogged within the streambed. With fragmented reaches, the vertical hydraulic conductivity of the streambed continued to drop by approximately 50-75%. The team then realized that the surfaces of reaches were waterless before rainfall events, and the dryness led to the death of large volumes of diatoms that grow in the stream, the remains of which were left deposited on the surface of the sediments (Figure 1), which is the speculated reason for the decrease in hydraulic conductivity. This suggests that the growth and death of diatoms could be the key to decreasing fragmentation events in streams.  This fragmented reach was previously a perennial one. Aside from cutting off the way home for the Formosan landlocked salmon, it is also worth continuous study on how such events impact the river’s ecosystem, including the proliferation and death of diatoms before and during the fragmentation period, and the transmission of matters after the streamflow recovers.  Figure 1. (Left) Dead diatoms scattered across the dry river course, (mid) a close-up of the riverbed and (right) diatoms under an electron microscope.   Reference:  Chiu, Y.C., Lee T.Y., Hsu, S.Y., Liao, L.Y., 2020. The effects of hydrological conditions and bioactivities on the spatial and temporal variations of streambed hydraulic characteristics at the subtropical alpine catchment. Journal of Hydrology, 584, 124665. https://doi.org/10.1016/j.jhydrol.2020.124665 

The Otherworldliness of Massive Volcanic Eruptions

November 09, 2021

Earth is the only terrestrial planet in the Solar System that has evolved, forming a Si- and Al-rich (sialic) crust. The formation and development of sialic or continental crust is a first order scientific issue that is not fully understood. However, with the discovery of plate tectonics, it appears that most continental crust is created at convergent plate boundaries via partial melting and accretion of primitive crust. The initiation of plate tectonics remains uncertain but likely began 2.8 to 2.5 billion years ago. In addition to convergent margins, continental crust is created and recycled within plates due to the voluminous emplacement of high temperature basaltic magma. These immense regions of primarily mafic magmatic rocks within continental crust are known as large igneous provinces (LIP). The Late Permian Emeishan large igneous province (ELIP) is one of the most comprehensively studied continental magmatic provinces in the world and covers ~300 000 km2 of southwestern China with displaced, correlative units in northern Vietnam. The ELIP is of tremendous geological interest because it hosts world-class ore deposits and is contemporaneous with a mass extinction. The majority of lavas and plutons were emplaced 260 ± 2 million years ago, and the principal volcanic unit of the ELIP is the flood basalts. However, there are also ultramafic and silicic lava flows and ore-bearing layered mafic-ultramafic and silicic plutonic rocks as well. The formation of the ELIP may be related to a combination of mantle sources that include the relatively shallow lithospheric mantle and the deep mantle.   The development of continental crust on Earth is a longstanding problem as the geological record prior to 4.0 billion years is poorly known. Knowledge on the formation of continental crust is based on the Archean rock record. The difficulties in understanding crust formation are related to the limitations of the rock record but also the possible tectonic processes that were operating on Earth at the time. The development of plate tectonics, in particular convergent plate boundary processes, permitted the creation of large volumes of sialic (Si- and Al-rich) continental crust. Furthermore, continental crust is created and recycled within plates and is associated with emplacement of voluminous high temperature primitive magma. These immense regions of basalt lava are known as mafic continental large igneous provinces (LIP).  The study of large igneous provinces requires a multidisciplinary approach to fully understand and characterize the thermal, biological and geological consequences of their formation. Mafic continental large igneous provinces are voluminous, spatially contiguous regions of the continental crust where mantle-derived volcanic rocks and their intrusive equivalents were emplaced over a short period (~10 Ma) of time. The formation of large igneous provinces is debated as many are considered to be derived by a diapiric upwelling of mantle material (mantle plume) possibly originating from the core-mantle boundary, whereas others are considered to be related to decompressional mantle melting associated with tensional plate stress also known as the “plate” model. The rapid emplacement of mostly mafic magma is often but not always associated with continental break-up and mass extinctions. Therefore the study of Phanerozoic LIPs has tremendous significance in understanding not only the secular thermal conditions of the lithosphere and plate tectonics but also how ecosystems respond to the effects of elevated rates of magmatism. Of particular interest is the Late Permian Emeishan large igneous province (ELIP) as it hosts numerous world-class base metal ore deposits and was contemporaneous with a mass extinction. Figure 1. Map of the Emeishan large igneous province (ELIP), Ailaoshan-Red River shear zone, and the Tu Le-Phan Si Pan region. A: Inset map of the major suture zones of eastern Asia. B: Simplified map of ELIP showing the distribution of the crustal zonation, and the position of the main flood basalt relative to the displaced Tu Le-Phan Si Pan region (from Shellnutt et al., 2020).   The Late (~ 260 Ma) Permian ELIP covers an area of ~ 0.3 × 106 km2 primarily along the western margin of the Archean to Paleoproterozoic Yangtze Craton of the South China Block, but fragments are identified within the Tibetan plateau and the Song Da zone of northern Vietnam (Fig.1). The emplacement of the ELIP overlaps with the end-Capitanian mass extinction and may have contributed to or was the primary cause of the extinction event. The flood basalts are volumetrically the largest unit of the ELIP and can be chemically subdivided into low- and high-Ti groups based on the Ti/Y ratios and bulk TiO2 content. Furthermore, there are relatively minor volumes of ultramafic and silicic volcanic rocks. The ultramafic lavas were amongst the first to erupt as they tend to be restricted to the lower half of the volcanic sequences whereas the silicic volcanic rocks are primarily found in the upper flow sequences. The volcanic rocks initially erupted at 263–262 Ma on top of and between deposits of middle Permian limestone and on Precambrian cratonic rocks of the Yangtze Craton (Fig.2). The youngest flows erupted at 257–256 Ma. The plutonic/intrusive rocks of the ELIP include: granites, Fe–Ti–V oxide ore-bearing layered mafic–ultramafic intrusions, and mafic dykes. Figure 2. A summary of the eruptive and plutonic magmatism of the Emeishan large igneous province. The Binchuan ignimbrite (white square) was deposited (206Pb/238U = 259.1 ± 0.5 Ma) at the Wuchiapingian-Capitanian boundary. The eruptive range of silicic ashes is 260 Ma to 257.3 Ma. The CA-ID TIMS 206Pb/238U ages of the Panxi mafic (grey triangle is mafic dyke) and silicic intrusive (grey square is Woshui syenite) rocks range from 259.6 ± 0.5 Ma to 257.6 ± 0.5 Ma. New results from the Tu Le rhyolite (TLR), Muong Hum granite (MH), Phan Si Pan granite (PSP) indicate that magmatism continued for an additional 1.5 million years and likely contributed to global cooling (from Shellnutt et al., 2020).   The evolution and development of the ELIP can be summarized thusly. During the Late Permian the Yangtze Block was a stable carbonate platform at tropical latitudes. The Emeishan volcanic rocks erupted along with the intrusion of several plutonic complexes. The majority of lavas erupted within a short period of time (260 ± 2 Ma) with volcanism tailing off by 257 Ma. The volcanic and the plutonic rocks are likely derived from magmas generated from a mantle plume source. The major and trace elemental and isotope composition of the Emeishan magmatic rocks indicate that the source was heterogeneous and possibly volatile-rich as is the case for some Ti-rich basaltic rocks. The subcontinental lithospheric mantle may or may not be involved but probably cannot be discerned with ease due to the isotopic heterogeneity of the rocks and the fact that the source may have been volatile-rich (e.g., CO2, F). The injection of mafic magmas induced partial melting of the Yangtze Block which led to the formation of some granite intrusions, whereas mingling between mafic magmas and crustal melts produced other granitic rocks. The mafic magmas that did not erupt but reached shallow crustal levels (i.e., < 3 km) crystallized and formed the cumulate layered mafic-ultramafic complexes, some of which produced both volcanic and plutonic silicic rocks (Fig.3). The formation of ore deposits within the layered intrusions is dependent on the depth of emplacement, the original parental magma composition, amount and timing of crustal assimilation including country rock volatile fluxing. It is possible, providing that magmatism was short lived, that country rock degassing contributed to climatic changes which adversely affected global ecosystems. Figure 3.  A summary of the tectonomagmatic evolution of the Emeishan large igneous province. At 260 Ma the ELIP plume head arrives at the base of the lithosphere possibly inducing uplift of the crust and decompressional melting of the plume source. Mafic magmas are injected into the lower crust/upper mantle forming chambers. Some magmas erupt onto the surface whereas others reach relatively shallow depths and formed the oxide-ore bearing layered intrusions and sulphide-ore bearing intrusions. The continuous injection of mafic magmas likely induced partial melting of the crust which leads to the formation of the crust-derived silicic plutons and possibly the hybrid silicic plutons (from Shellnutt, 2014).     Source: Shellnutt, J.G., Pham, T.T., Denyszyn, S.W., Yeh, M.-W., Tran, T.A., 2020. Magmatic duration of the Emeishan large igneous province: insight from Northern Vietnam. Geology 48, 457-461. Shellnutt, J.G. 2014. The Emeishan large igneous province: a synthesis. Geoscience Frontiers 5, 369-394. 

The Magic of Transforming Carbon Dioxide to Ethanol: An Analysis of Copper-Based Electrochemical Catalysts

November 09, 2021

(This report is provided by Dr. Ming-Kang Tsai’s research team in the Department of Chemistry) Copper electrocatalysts have been shown in the past literature to selectively reduce carbon dioxide to hydrocarbons. However, due to the lack of systematic studies on time-scale resolved spectral features, the selectivity resulted from the surface atomic characteristics of the copper catalyst– could be copper metal or copper oxide, along the reaction path remains uncertain. This study introduces an X-ray absorption spectrum with a few seconds resolution scale to observe the chemical state evolution of catalysts in reactions. Under specific experimental conditions, it was observed that the average oxidation state consisted of the mixed oxidation states on the surface of copper material could be stably maintained on the electrode surface, thus steadily increasing the effective yield of ethanol. Combined with the first-principles simulations, the catalytic reaction pathway of CO2 conversion can be derived step-by-step and verified by experimental observations.   Since the Industrial Revolution, the use of energy by humans and society has increased dramatically. In order to meet the energy shortage required for the stable operation of national societies, fossil fuels such as oil, coal, and natural gas, which have long been stored in the earth's crust, are extracted through the enhancement of drilling technology and converted into electric, mechanical, or thermal energy for daily use through chemical combustion reactions. As a result, the emission of carbon dioxide (CO2) into the atmosphere seems to be a necessary evil for technological progress. The National Oceanic and Atmospheric Administration of the USA (NOAA) has been observing the rising trend of CO2 concentration in the atmosphere for a long time, and this concentration has reached record highs several times in recent years (Figure 1: over 400 ppm). The global greenhouse effect caused by high CO2 concentration is gradually affecting the living environment of human beings, such as the rising sea level and extreme climate events. In view of this, the effective recovery and conversion of CO2 gas emissions into secondary useable fuels in chemical technology has become an important issue for countries to complete the circular economy model.   Figure 1: CO2 Atmospheric Concentration and Emissions (Source: www.noaa.gov)     CO2 is chemically the highest oxidation state of the carbon, meaning that it cannot react with oxygen for further combustion. If CO2 is to be converted into other fuels, it must be converted into other hydrocarbons under reaction conditions that provide electrons and hydrogen, which is chemically known as a reduction reaction. The possible reaction pathways are shown below: 　　CO2 + 2e– + 2H+ → H2O + CO (Carbon monoxide; one of the raw materials required for industrial processes) 　　CO2 + 2e– + 2H+ → HCOOH (Formic acid; antiseptic and antibacterial properties) 　　CO2 + 4e– + 4H+ → H2O + HCHO (Formaldehyde; raw material for industrial resins)  　　CO2 + 6e– + 6H+ → H2O + CH3OH (Methanol; can be used as cell fuel) 　　CO2 + 8e– + 8H+ → 2H2O + CH4 (Methane; one of the components of natural gas) 　　2CO2 + 12e– + 12H+ → 4H2O + C2H4 (Ethylene; an important raw material for polymer synthesis) 　　2CO2 + 12e– + 12H+ → 3H2O + C2H5OH (Ethanol or commonly known as alcohol; has fuel and medical uses)   From the reaction pathways listed above, it can be seen that there are many options for CO2 conversion. The higher the molecular weight of the product, the higher the technological threshold to be overcome. The effective conversion of CO2  to ethanol is a topic of interest for many scientists and has considerable potential economic value. From the precious scientific literature, copper metal is a special electrode material that can convert CO2 into various hydrocarbons simultaneously in an electrochemical reaction environment (i.e., lack of single product selectivity). From a chemical process point of view, the more efficiently a single product can be synthesized, the higher the potential for technological applications to be derived from it. Copper oxide is a common product in the rusting of metallic copper, and through proper preparation, a special material can be produced that contains both cuprous (monovalent copper ions) and metallic copper on its surface. The previous scientific  literature has reported that the presence of mixed oxidation states (i.e., divalent copper ions, cuprous ions, or metallic copper) on the surface of copper materials can  effectively assist in the conversion of carbon dioxide to products containing carbon chemical bonds such as ethylene or ethanol. The formation of carbon-carbon bonds can be carried out by the heterogeneous bonding steps of CO dimerization. Through the unique intermittent pressure control technique and the monitoring of the in-situ spectral signal (X-ray absorption spectroscopy with a few seconds resolution scale), it was observed that the average oxidation state consisted of the mixed oxidation states on the surface of copper material can be steadily maintained at the electrode surface under specific experimental conditions, thus steadily increasing the effective production of ethanol (Figure 2).   Fig. 2: Distribution of electrochemical catalytic products of CO2 During the study, the crystalline surface of Cu metal mixed with Cu2O (110) simulated by first-principles calculations could play a key role in elucidating the ethanol synthesis pathway (Figure 3). In the highly oxidized (as opposed to metallic)  surface blocks rich in cuprous copper, the hydroxide functional group is an important factor in the protection of oxygen-containing intermediates in the CO2 reduction process through the attractive inter-dipole interactions. Figure 3: Predicted free energy profile of C-C bond formation (liquid-solid interface simulation at the full atomic scale)   This research was conducted by a team from National Taiwan Normal University (NTNU) to simulate and explore the crystalline surfaces of various copper surfaces, to identify highly reactive interfaces, and to rationalize the reaction mechanism. The theoretical prediction results were compared with the experimental observations – materials synthesis and in-situ spectroscopy analysis by Prof. Hao-Ming Chen's group in the Department of Chemistry, National Taiwan University. Through the collaboration of bilateral research teams, the synthesis and characterization of this novel Cu-based electrocatalysts were successfully carry out to explore the reaction mechanism for the conversion of CO2 to ethanol.   Reference: "Operando Time-resolved X-ray Absorption Spectroscopy to Unravel the Chemical Nature: Chemical State-Trapping Strategy Enabling the Highly Selective CO2 Reduction", Sheng-Chih Lin, Chun-Chih Chang, Shih-Yun Chiu, Hsiao-Tien Pai, Tzu-Yu Liao, Chia-Shuo Hsu, Ming-Kang Tsai,* Hao Ming Chen,* Nat. Commun. 2020, 11, 3235. https://www.nature.com/articles/s41467-020-17231-3

Quick home test for Parkinson's medication adjustment: Detection of L-DOPA in blood using enzyme colorimetry

May 10, 2021

(This report is provided by Dr. YiChun Yeh’s research team in the Department of Chemistry) Parkinson's disease is a neurological disorder that primarily affects motor performance. L-DOPA is the precursor of dopamine (DA) synthesis in the body and is widely used in the treatment of Parkinson's disease. However, because of the side effects associated with these drugs, clinical adjustments to the medication are often required. Therefore, measuring the concentration of L-DOPA in patients is an issue of interest for many researchers. Several methods have been developed to detect the concentration of L-DOPA, such as electrochemical assay and liquid chromatography, but there are still some limitations. In this study, a simple enzymatic colorimetric method was developed to selectively identify and oxidize L-DOPA by oxidative enzymes, resulting in a yellow product that can be identified by the naked eye; the concentration of L-DOPA can be inferred from the color intensity. Therefore, it can be used as a quick and easy estimation of the L-DOPA concentration in the test body, which is expected to be used as an indicator and reference for drug formulation.   Parkinson's disease is a complex brain disorder that mainly affects motor performance, so doctors will make a judgment and diagnosis clinically based on the patient's motor development and neurological examination. According to statistics, people over the age of 65 have a prevalence rate of 1-2%, so it is estimated that more than 40,000 people in Taiwan are affected by Parkinson's disease. Parkinson's disease is a complex cause of neuronal degeneration in the brain. When the nerve cells in the brain are damaged or die, they cannot produce and send the chemical substance (dopamine) that is used to transmit information, so the movement signals associated with it cannot be transmitted. When there is not enough dopamine (DA), there is too much acetylcholine, and the balance between these two chemicals becomes abnormal, resulting in tremors and muscle stiffness in many patients. Today's treatment for Parkinson's disease focuses on increasing DA secretion, and therefore the main drug used is L-dihydroxyphenylalanine (L-DOPA). The formation of DA is catalyzed by enzymes to compensate for the lack of DA. However, because of the side effects associated with these drugs (e.g., causing hallucinations or confusion), strict clinical monitoring and adjustment of medication are often required. In the past, many monitoring methods required long periods of time and expensive equipment for effective monitoring, making it difficult for patients to manage their conditions at home. Therefore, the enzyme colorimetric method developed in this study is expected to overcome the above limitations and also has good detection capability. In this experiment, a colorimetric biosensor was designed to detect L-DOPA mainly by the production of betaine aldehyde amine. The production of betaine aldehyde amine has an obvious yellow color visible to the naked eye, and the characteristic peak at 430 nm wavelength can be clearly observed through the absorption spectrum. Selective experiments on other neurotransmitters with similar structures (e.g., dopamine, epinephrine, norepinephrine, and some metabolite intermediates) have demonstrated good selectivity of this method for L-DOPA. After confirming the good selectivity of the designed sensor for the analyte, we can further test the relationship between the absorption values obtained at different concentrations of the analyte to be detected. The color rendering showed a good linear relationship with respect to concentration in the range of 5-500 μM, with a detection limit of 2.8 μM. Next, through the chemical reaction of aldehyde amine condensation, we convert yellow betulinic acid into derivatives with green and red fluorescence to enhance the sensitivity of the detection and to reduce the background interference of the detectors. In short, this study has successfully developed a colorimetric biosensor for rapid detection, and demonstrated its sensitivity and high selectivity through experiments. This type of enzyme colorimetric method is a worthy field of development because it can achieve the purpose of instant detection without the need to carry instruments or for professional personnel.       Reference:  https://www.sciencedirect.com/science/article/pii/S0925400519309189  

Detecting the size of primordial black holes with superhorizon perturbations

April 07, 2021

 (This report is provided by Dr. Wolung Lee’s research team in the Department of Physics) At the onset of the cosmic journey, the inflationary mechanism produced superhorizon curvature perturbations which affected the future formation of the universe. This study analyzed the growth of superhorizon curvature perturbations in the inflationary universe. Using a simple ultraslow-roll model, we derived the coherence function between any two points in the curvature perturbation. It showed that the causality limits the growth of the curvature perturbation, thereby constraining the important inflationary slow-roll parameters, allowing the universe to produce a large enough primordial black hole. Our research will help estimate how curvature perturbations form primordial black holes in the universe.   The consensus is that if the primeval universe (i.e., the beginning of the universe) had experienced a phase of rapid inflation, it would explain why the current universe is so homogeneous and isotropic. A single, flat, simple scalar field drives the occurrence of slow-roll inflation, producing vacuum fluctuations beyond the size of the horizon, and these quantum fluctuations eventually derive almost scale-independent curvature perturbations, including matter density fluctuations and gravity waves. Employing the concept of slow-rolling inflation, cosmological observations have made extremely precise measurements on matter density perturbation in recent years. Recently, scientists have observed gravity waves emitted by merging black holes (2017 Nobel Prize in Physics), making people more curious about the origin of primordial black holes. Many studies have used different models of inflation to try to generate large enough curvature perturbations during inflation to form primordial black holes to explain the sources of gravity waves detected by the Laser Interferometer Gravity Wave Observatory (LIGO).　 Among many models, there is an ultraslow-roll inflation model with a delayed inflection point in its gravitational field, which violates the slow-roll condition but generates large enough curvature perturbations to arouse our interest. We thus analyze the evolution of the super-visual perturbation in such an ultraslow-roll model. The concept of the conservation of the superhorizon perturbation derived from the assumption of the slow-roll condition no longer holds when the universe is in the ultraslow-roll stage; therefore, the matter disturbance in the superhorizon mode can grow rapidly. Although the rate of inflation is extremely low and the acceleration of the spatial expansion is extremely large, the material disturbance in the superhorizon mode can indeed grow rapidly. However, this growth is not unlimited and is still restricted by the causality law, thus allowing us to estimate an upper limit on the growth rate of curvature perturbations. After lengthy numerical calculations and comparing with the Cosmic Microwave Background (CMB) observations, we found that the presence of the anti-curvature point significantly reduces an important slow-roll parameter in the inflation model, resulting in a well-defined spike on the power spectrum of curvature perturbations, about halfway through the inflation, forming the primordial black hole of about 10-8 solar masses!  The results of our analysis can be applied to infer the growth of curvature perturbations in the universe during ultraslow-roll inflation, and we can then estimate the mass range and quantity of primordial black holes formed when these curvature perturbations re-enter our horizon, which can be compared with current observations to confirm the origin of gravity waves.   Reference:https://journals.aps.org/prd/abstract/10.1103/PhysRevD.99.063524 

Transformers in The Porous Materials Field: Extremely Fast Lattice Rearrangement of the MOF Structures

September 15, 2020

In this work, we present a case system that can achieve rapid structural rearrangement of the whole lattice of a metal–organic framework (MOF) through a ‘domino’ alteration of the bond connectivity under mild conditions. Topological transitions between significantly different phases typically require extreme conditions to collectively break chemical bonds and overcome the stress caused to the original structure by altering its correlated bond environment. Our system transforms from a disordered and less crystalline MOF with low porosity to a highly crystalline and porous isomer within few minutes upon activation (solvent exchange and desorption), resulting in a significant increase in surface area, from 725 to 2,749 m2/g. Spectroscopic measurements show that this counter-intuitive lattice rearrangement involves a metastable intermediate with defect frameworks that results from solvent removal on coordinately unsaturated metal sites. This less crystalline–crystalline switch between two topological distinct MOFs is shown to be reversible over four cycles through activation and re-immersion in polar solvents. The aim of this study was to investigate the partial defects in real MOF crystalline structures and to focus on defect-induced MOF properties, which are expected to enhance and develop the physical, mechanical, electronic and optical material properties and chemical activities of MOF materials. This research adopted an exploratory experimental procedure that facilitated the synthesis of highly porous MOFs, which were previously not easy to synthesize, and functional applications for defective and highly porous MOFs were further developed.   Metal-Organic Framework (MOF) porous material is a new type material that can be described as nano-sized houses or sponges with a surface area of up to the size of a football field in a single gram. Therefore, many highly promising industrial applications are developed in separation, adsorption, catalysis, photovoltaics, medicine and energy. However, the synthesis of such a nano house of MOF typically takes several days of chemical reaction time. This study proposed a novel and rapid fabrication procedure for constructing MOF nano-houses. The research focused on defect-induced MOF synthesis properties in the presence of partial defects in the MOF crystal structure, and further enhanced and developed the physical, mechanical, electronic and optical material properties and chemical activities of MOF materials. It was found that an exploratory experimental procedure allowed for the breakthrough synthesis of highly porous MOFs, which were previously difficult to synthesize, and further developed functional applications for defective and highly porous MOFs. A new phenomenon in porous MOF materials has been discovered - an extremely rapid rearrangement of the overall lattice structure of MOFs can be achieved through changes in chemical bonding under mild conditions (Figure 1). After activation (i.e., solvent exchange and desorption) of the system, the structure can be transformed from a low porosity and disordered MOF to a high porosity and crystalline isomer within minutes, resulting in a significant increase in specific surface area from approximately 725 m2/g to 2,749 m2/g. The lattice rearrangement of this MOF system was shown by spectral measurements to involve the formation of meta-stable intermediate states with defective skeletons, resulting from the removal of ligand unsaturation and the removal of solvents from the metal sites. The amorphous-crystalline transition between the topologies of these two different MOFs can be accomplished in several reversible structural cycles through activation and re-immersion in polar solvents (Figure 2).  This research has revealed for the first time that porous MOF materials can be transformed in just a few minutes in a way that is like the transformer in the movie. This new discovery can be used to synthesize MOF porous materials that were previously difficult to synthesize experimentally, and to further develop functional applications for defective and highly porous MOF.   Fig. 1: Extremely rapid rearrangement of the overall lattice structure of an aluminum metal organic backbone (MOF) hole material Fig. 2: Schematic diagram of the reversible structural cyclic transformation of the lattice structure of an aluminum metal organic backbone (MOF) hole material

Can a glass of red wine help prevent Cancer? Quantifying resveratrol in red wines

June 02, 2020

A large amount of red wine contains phenolic substances, of which "Resveratrol" is one of them. Resveratrol is a compound from plant which can protect against bacterial invasion, and contains multiple naturally occurring phenolic plant antitoxins. Studies have confirmed that it has anti-cancer, anti-inflammatory, and metabolic effects. The research on “Resveratrol” started through the slogan “French paradox in 1980, which describes improved cardiovascular outcomes despite a high fat diet in French people who are in the habit of drinking red wine. Since then, resveratrol has been widely studied and discussed. ” In the whole research process, the sample preparation is a critical step. This present work used the direct dilution method and the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) pretreatment technology. Subsequently, efficient QuEChERS extraction combined with LC-MS/MS (high performance liquid chromatography tandem mass spectrometry) for the quantitative analysis of resveratrol in red wines was successfully developed and verified in this study. Furthermore, QuEChERS extraction can be used not only in multiplex detection of pesticide residues in fruits and vegetables, but also red wine study. The proposed method will help the future application in the fields of food analysis.     For a long time, the "French paradox" has been explored in order to understand whether the habit of drinking red wine can reduce the risk of cardiovascular disease. Previous study found the benefits of red wine in addition to anthocyanin and tannic acid, of which the biggest contributor maybe is resveratrol. Phytotoxins naturally produced in certain plants are attacked by pathogens. They are a polyphenol compound, a powerful antioxidant that can protect human cells from free radical damage.  After long-term research, trans-resveratrol has been shown to potentially have anti- cancer, anti-inflammatory, and anti-cardiovascular disease properties, and can even regulate metabolism. Health is the common goal pursued by modern people, and prevention and health care are indispensable. The complete analysis method includes sample collection, sample pre-processing, instrument analysis and data processing, of which the sample preparation process is the key. In order to detect small amounts of trans-resveratrol in red wine samples with complex matrices, it is necessary to develop a sensitive and reliable detection method. The QuEChERS pretreatment technology proposed in recent years is different from the traditional extraction of target analytes. It uses adsorbents to remove matrix interference from complex samples to improve the recovery of target analytes in the pretreatment process. The original aim was to establish a fast and low-cost pretreatment method for pesticide residue detection for fruit and vegetables. This study is based on technology and optimizes the pretreatment of red wine samples to achieve the best efficiency. Through the sorbent selection and the adjustment of the usage ratio, it is possible to establish an analytical method for the separation of the trans and the cis resveratrol isomers. Finally, with a liquid chromatography tandem mass spectrometry (HPLC-MS/MS), a series of detection methods specifically designed to quantify trans-resveratrol in red wine was developed. In the process of developing analytical methods, pre-processing steps are a very important part. This experiment was based on the QuEChERS technology to optimize extraction conditions with the adsorbent selection, and was applied to the red wine sample, reducing the time and cost involved, and improving analyte recovery to achieve the best benefits and prove that the QuEChERS technology is not simply limited to the use of pesticide residues. On the other hand, in order to evaluate that the concentration of trans-resveratrol in red wine will decay over time, the concentration of red wine that was opened and stored in the refrigerator was tracked. The final result indicated that the concentration of trans-resveratrol in red wine will not be significantly lost within one week of opening the bottle, which shows that the stability of trans-resveratrol is high. The habit of drinking red wine is common all around the world and is inseparable from health. This research has successfully developed and verified a method specifically designed to quantify trans-resveratrol in red wine. The method is optimized based on the QuEChERS technology and was applied to the pretreatment of red wine samples. It was able to reduce the sample matrix effect, and with LC-MS/MS, could separate and detect isomers with the highly sensitive approach. The results of this report will help the future application of this technology in the fields of food and biological sample analysis.

Exploring reality in the virtual: Design and analysis of catalyst materials in theoretical computational chemistry

May 05, 2020

Theoretical computational chemistry was first developed in the 1970s. In 1998, this community was with the Nobel Prize to affirm its profound influence on quantum chemistry. The ability to describe real chemical reactions has been greatly advanced by hybrid algorithms combining classical and quantum mechanics. In 2013, the theoretical computational chemistry was again awarded with the Nobel Prize. Chemical events that appear in the virtual numerical world become the important information useful in contemporary development of chemical process technology. For half a century, human society has burned fossil fuels to obtain energy, leading to ever-increasing greenhouse gases. This has become a problem that must be overcome if a global sustainable economy is to be maintained. Energy generated through solar power, combined with advanced catalytic electrode materials, carbon dioxide, and water, can produce electrolysis, converting energy into hydrocarbon fuel and oxygen. This is one recognized solution in the development of energy technology. Hybrid algorithms mixed with classical and quantum mechanics can be employed in computer models to analyze the interaction of carbon dioxide and water molecules on the surfaces of electrode materials, and summarize the various chemical bonding or breaking events that occur during molecular conversion. Catalyst materials can be modified and redesigned to eliminate difficult reaction steps. These methods can be employed to conduct systematic comparative analyses in the virtual world, providing effective improvements in the actual chemical process and reducing both exploration/discovery time and development costs. The significant amount of digital data accumulated, coupled with the statistical methods of big data analysis, has resulted in novel and promising material designs, ushering in the next generation of experimental synthesis. Research and development models that effectively combine chemical processes and computational analyses will soon be mainstream, leading to future technological progress.   The concentration of carbon dioxide in the atmosphere continues to rise, and as a result, humans are facing global challenges such as global warming, extreme weather, rising sea levels, ecological crises, ocean acidification, etc. Therefore, the carbon dioxide in exhaust gas must be converted into useful chemical substances. It is essential that this problem be solved. One successful example is when natural photosynthesis occurs in plants; the carboxylated enzyme RuBisCO absorbs CO2 molecules, synthesizing new multi-carbon hydrocarbons in the Calvin cycle. In the chemical industry, scientists have actively developed various carbon dioxide conversion methods. In the past literature, metal electrodes have been used to carry out electrocatalytic reactions to reduce carbon dioxide in aqueous solutions. After comparing many metal electrodes (e.g., gold, silver, zinc, palladium, gallium, lead, mercury, indium, tin, cadmium, thallium, nickel, iron, platinum, titanium), researchers found that only copper electrodes could directly generate multi-carbon hydrocarbons. Full use of solar power should be considered as a means of generating electricity and developing appropriate catalytic electrodes to convert electrical energy, carbon dioxide, and water through electrocatalysis. The product could then be stored as chemical energy, significantly improving the efficiency of renewable energy. In 2018, Professor Tsai’s team simulated the formation of OCCO on the surface of three copper oxides (i.e., CuO, Cu4O3, and Cu2O). The team first theoretically proposed that OCCO could be effectively synthesized on the surface of Cu4O3, in the presence of surface defects. The team’s conclusions were published in the PCCP journal of the Royal Society of Chemistry. In 2019, the German Siemens lab repeated the predictions made by the National Taiwan Normal University team, successfully producing the electrode catalyst Cu4O3 and converting CO2 into ethylene (C2H4).   Figure 1: Potential energy surface prediction.   OCCO, an unstable intermediate, has a long molecular structure. In 2019, Professor Tsai’s team used its self-developed classical quantum hybrid simulation method to adjust the lattice structure of the copper electrode material to shape a long structure surface suitable for OCCO, further predicting that the long adjusted crystal lattice might be more suitable for synthesizing three-carbon hydrocarbons. Their research was published in the PCCP journal that same year. Figure 2: Hybrid model of CO electrocatalytic coupling on copper electrode surface.   In addition to the reduction of carbon dioxide, Professor Tsai's team has collaborated with Professor Chen Hao Ming's lab at the National Taiwan University to analyze iron-cobalt composite electrodes, exploring how to reduce the difficulty of splitting water molecules (a key step in hydrogen energy generation). Through live X-ray spectrum analysis combined with computer simulations of quantum chemistry, the team identified the roles of iron and cobalt on the surface of the electrode, successfully fabricating and analyzing the high electrocatalytic activity of the iron-cobalt composite electrode. The research results were published by the American Chemical Society in 2018. Figure 3: Schematic diagram of the reaction path of water oxidation on the surface of cobalt and iron-cobalt composite electrodes. Theoretical computational chemistry can provide many opportunities for exploration that cannot be attempted in experimental conditions. By combining physical theory, programming, and chemical reaction principles, as well as the computing power of high-speed computers (for example, what is available from the National High-Speed Network and Computing Center, using the National Taiwan Normal University’s cloud computing platform), potential chemical reaction conditions can be predicted. Professor Tsai believes that the successful integration of theoretical computational chemistry and actual processing of experiments will become key factors in the advancement of renewable energy technology.   Reference "Identification of Stabilizing High-valent Active Sites by Operando High-energy Resolution Fluorescence-detected X-ray Absorption Spectroscopy for High Efficient Water Oxidation", Sung-Fu Hung,+ Yu-Te Chan,+ Chun-Chih Chang, Ming-Kang Tsai,* Yen-Fa Liao, Nozomu Hiraoka, Chia-Shuo Hsu, Hao Ming Chen,*J. Am. Chem. Soc.2018, 140, 17263-17270. Link: https://doi.org/10.1021/jacs.8b10722 "A Computational Exploration on CO2 Reduction via CO Dimerization on Mixed-Valence Copper Oxide Surface", Chun-Chih Chang, Elise Y. Li,* Ming-Kang Tsai,* Phys. Chem. Chem. Phys.2018, 20, 16906-16909. Link: https://doi.org/10.1039/C8CP00592C "Enhancing C-C Bond Formation by the Surface Strain: Investigating the C2 and C3 Intermediate Formation on the Strained Cu Surfaces", Yu-Te Chan, I-Shou Huang, Ming-Kang Tsai,*Phys. Chem. Chem. Phys.2019, 21, 22704-22710. Link: https://doi.org/10.1039/C9CP02977J