Publications in the Year: 2016

Conference Paper

Palazzetti, F, Lombardi A, Yang S-J, Nakamura M, Kasai T, Lin K-C, Che D-C, Tsai P-Y.  2016.  Stereodirectional photodynamics: Experimental and theoretical perspectives. AIP Conference Proceedings. 1790 Abstract

Hexapole oriented 2-bromobutane is photodissociated and detected by a slice-ion-imaging technique at 234 nm. The laser wavelength corresponds to the C - Br bond breaking with emission of a Br atom fragment in two accessible fine-structure states: the ground state Br (2P3/2) and the excited state Br (2P1/2), both observable separately by resonance-enhanced multiphoton ionization (REMPI). Orientation is evaluated by time-of-flight measurements combined with slice-ion-imaging. © 2016 Author(s).
Palazzetti, F, Lombardi A, Nakamura M, Yang S-J, Kasai T, Lin K-C, Tsai P-Y, Che D-C.  2016.  Rotational state-selection and alignment of chiral molecules by electrostatic hexapoles. AIP Conference Proceedings. 1790 Abstract

Electrostatic hexapoles are revealed as a powerful tool in the rotational state-selection and alignment of molecules to be utilized in beam experiments on collisional and photoinitiated processes. In the paper, we report results on the application of the hexapolar technique on the recently studied chiral molecules propylene oxide, 2-butanol and 2-bromobutane, to be investigated in selective photodissociation and enantiomeric discrimination. © 2016 Author(s).

Journal Article

Nakamura, M, Yang S-J, Tsai P-Y, Kasai T, Lin K-C, Che D-C, Lombardi A, Palazzetti F, Aquilanti V.  2016.  Hexapole-Oriented Asymmetric-Top Molecules and Their Stereodirectional Photodissociation Dynamics. Journal of Physical Chemistry A. 120:5389-5398., Number 27 AbstractWebsite

Molecular orientation is a fundamental requisite in the study of stereodirected dynamics of collisional and photoinitiated processes. In this past decade, variable hexapolar electric filters have been developed and employed for the rotational-state selection and the alignment of molecules of increasing complexity, for which the main difficulties are their mass, their low symmetry, and the very dense rotational manifold. In this work, for the first time, a complex molecule such as 2-bromobutane, an asymmetric top containing a heavy atom (the bromine), was successfully oriented by a weak homogeneous field placed downstream from the hexapolar filter. Efficiency of the orientation was characterized experimentally, by combining time-of-flight measurements and a slice-ion-imaging detection technique. The application is described to the photodissociation dynamics of the oriented 2-bromobutane, which was carried out at a laser wavelength of 234 nm, corresponding to the breaking of the C-Br bond. The Br photofragment is produced in both the ground Br (2P3/2) and the excited Br (2P1/2) electronic states, and both channels are studied by the slice imaging technique, revealing new features in the velocity and angular distributions with respect to previous investigations on nonoriented molecules. © 2016 American Chemical Society.
Dhenadhayalan, N, Lee H-L, Yadav K, Lin K-C, Lin Y-T, Chang AHH.  2016.  Silicon Quantum Dot-Based Fluorescence Turn-On Metal Ion Sensors in Live Cells. ACS Applied Materials and Interfaces. 8:23953-23962., Number 36 AbstractWebsite

Multiple sensor systems are designed by varying aza-crown ether moiety in silicon quantum dots (SiQDs) for detecting individual Mg2+, Ca2+, and Mn2+ metal ions with significant selectivity and sensitivity. The detection limit of Mg2+, Ca2+, and Mn2+ can reach 1.81, 3.15, and 0.47 μM, respectively. Upon excitation of the SiQDs which are coordinated with aza-crown ethers, the photoinduced electron transfer (PET) takes place from aza-crown ether moiety to the valence band of SiQDs core such that the reduced probability of electron-hole recombination may diminish the subsequent fluorescence. The fluorescence suppression caused by such PET effect will be relieved after selective metal ion is added. The charge-electron binding force between the metal ion and aza-crown ether hinders the PET and thereby restores the fluorescence of SiQDs. The design of sensor system is based on the fluorescence "turn-on" of SiQDs while in search of the appropriate metal ion. For practical application, the sensing capabilities of metal ions in the live cells are performed and the confocal image results reveal their promising applicability as an effective and nontoxic metal ion sensor. © 2016 American Chemical Society.
Veerakumar, P, Panneer Muthuselvam I, Hung C-T, Lin K-C, Chou F-C, Liu S-B.  2016.  Biomass-Derived Activated Carbon Supported Fe3O4 Nanoparticles as Recyclable Catalysts for Reduction of Nitroarenes. ACS Sustainable Chemistry and Engineering. 4:6772-6782., Number 12 AbstractWebsite

Highly porous beetroot-derived activated carbons incorporated with well-dispered magnetite nanoparticles (Fe3O4 NPs; average size ca. 3.8 ± 0.5 nm) were fabricated via a microwave-assisted synthesis route. The magnetic Fe3O4@BRAC catalysts so-fabricated were characterized by a variety of diffent physicochemical teniques, viz. XRD, FE-TEM, VSM, gas physisorption/chemisorption, TGA, XPS, Raman, ICP-AES, and FT-IR spectroscopy. The as-prepared catalysts were exploited for heterogeneous-phase reduction of a series of nitroaromatics (RNO2; R = H, OH, NH2, CH3, and COOH) under KOH as a base, isopropyl alcohol acting as a hydrogen donor as well as solvent and also tested with other solvents. The reaction system not only exhibits excellent activity with high anilines yield but also represents a green and durable catalytic process, which facilitates facile operation, easy separation, and catalyst recycle. © 2016 American Chemical Society.
Dhenadhayalan, N, Lin K-C, Suresh R, Ramamurthy P.  2016.  Unravelling the Multiple Emissive States in Citric-Acid-Derived Carbon Dots. Journal of Physical Chemistry C. 120:1252-1261., Number 2 AbstractWebsite

Steady-state and time-resolved fluorescence spectroscopy techniques were used to probe multifluorescence resulting from citric-acid-derived carbon dots (C-dots). Commonly, both carboxyl-/amine-functionalized C-dots exhibit three distinct emissive states corresponding to the carbon-core and surface domain. The shorter-wavelength fluorescence (below 400 nm) originates from the carbon-core absorption band at ∼290 nm, whereas the fluorescence (above 400 nm) is caused by two surface states at ∼350 and 385 nm. In addition to three emissive states, a molecular state was also found in amine-functionalized C-dots. Time-resolved emission spectra (TRES) and time-resolved area normalized emission spectra (TRANES) were analyzed to confirm the origin of excitation wavelength-dependent fluorescence of C-dots. The surface functional groups on the C-dots are capable of regulating the electron transfer to affect the multifluorescence behavior. The electron transfer takes place from the carbon-core to surface domain by the presence of -COOH on the surface and vice versa for the case of -NH2 present on the surface. To the best of our knowledge, this is the first report that the multiemissive states are probed in C-dots systems using TRES and TRANES analyses, and related fluorescence mechanisms are verified clearly. © 2015 American Chemical Society.
Lin, K-C.  2016.  Regulation of nonadiabatic processes in the photolysis of some carbonyl compounds. Physical Chemistry Chemical Physics. 18:6980-6995., Number 10 AbstractWebsite

Carbonyl compounds studied are confined to acetyl halide (CH3COCl), acetyl cyanide (CH3COCN), acetyl sulfide (CH3COSH), acetaldehyde (CH3CHO), and methyl formate (HCOOCH3). They are asymmetrically substituted, but do not follow the well-known Norrish type I reactions. Each compound ejected in an effusive beam at about 300 K is commonly excited to the 1(n, π∗)CO lower state; that is, a nonbonding electron on O of the C=O group is promoted to the antibonding orbital of π∗CO. The photolysis experiments are conducted in the presence of Ar gas and the corresponding fragments are detected using time-resolved Fourier-transform Infrared (FTIR) emission spectroscopy. The enhancement of the collision-induced internal conversion or intersystem crossing facilitates the dissociation channels via highly vibrational states of the ground singlet (So) or triplet (T1) potential energy surfaces. In this manner, an alternative nonadiabatic channel is likely to open yielding different products, even if the diabatic coupling strength is strong between the excited state and the neighboring state. For instance, the photodissociation of CH3COCl at 248 nm produces HCl, CO, and CH2 fragments, in contrast to the supersonic jet experiments showing dominance of the Cl fragment eliminated from the excited state. If the diabatic coupling strength is weak, dissociation proceeds mainly through internal conversion, such as the cases of CH3COCN and CH3COSH. The photodissociation of CH3COCN at 308 nm has never been reported before, while for CH3COSH matrix-isolated photodissociation was conducted that shows a distinct spectral feature from the current FTIR method. The CH3CHO and HCOOCH3 molecules belong to the same type of carbonyl compounds, in which the molecular products, CO + CH4 and CO + CH3OH, are produced through both transition state and roaming pathways. Their products are characterized differently between molecular beam and current FTIR experiments. For instance, the photodissociation of HCOOCH3 at 248 nm yields CO with the vibrational state v ≥ 4, in contrast to the molecular beam experiments producing CO at v = 1. The photodissociation of CH3CHO at 308 nm intensifies a low energy component in the CH4 vibrational distribution, thus verifying the transition state pathway for the first time. © the Owner Societies 2016.