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Reusability, Long-Life Storage and Highly Sensitive Zirconium Nitride (ZrN) Surface-Enhanced Raman Spectroscopy (SERS) Substrate Fabricated by Reactive Gas-Timing Rf Magnetron Sputtering
(2023-12-22)
Sucheewa, Nguentra
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Wongwiriyapan, Winadda
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Rattanawarinchai, Prapakorn
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Wuttikhun, Tuksadon
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Sinthiptharakoon, Kittiphat
Transition metal nitrides (TMN) are promising material alternative to replace noble metals in the field of plasmonic applications, especially surface-enhanced Raman spectroscopy (SERS). Here we demonstrate a practical surface enhanced Raman spectroscopy (SERS) substrate using zirconium nitride (ZrN) thin films grown by reactive gas-timing (RGT) rf magnetron sputtering. The tailored properties of ZrN thin film exploited for SERS activity could be achieved to obtain a highly sensitive ZrN thin film SERS substrate with the enhancement factor (EF) of 1.24 × 106 and 4.8 %RSD at 1626 cm-1 toward methylene blue (MB) analyte which are comparable to the optimized Au sputtered thin films (EF=1.18 × 106 and with 5.1%RSD). We find that the spatial plasmonic hotspots on the surface of ZrN SERS substrate controlled by the turn-on timing of Ar:N2 sputtered gas sequence, leading to the discrete conductive surface profile, strongly relates to non-stoichiometric composition and the degree of (200)-oriented texture at the surface of ZrN thin film. Furthermore, ZrN thin film SERS substrates exhibit an excellent recyclability more than 30 cycles with simple cleaning process and a storage time longer than 6 months. The detection and reusability of ZrN SERS substrate on the low concentration of trinitrotoluene (TNT) for homeland security are also performed.
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Mechanistic investigation of Ni and NiCu for catalytic transfer hydrogenation of methyl levulinate to γ-valerolactone: A combined experimental and DFT study
(2023-06-25)
Chitpakdee, Chirawat
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Boonyoung, Pawan
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Pansakdanon, Chaianun
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Suttisintong, Khomson
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Faungnawakij, Kajornsak
Recently various supported bimetallic catalysts have been employed as effective catalysts for γ-valerolactone (GVL) production from levulinic acid or its esters. However, previous reports have shown synergetic roles of active metals and supports as important keys for superior catalytic performance. This work combines both experimental and simulation studies to focus solely on the role of bimetallic formation between nickel (Ni) and copper (Cu). The experimental results suggest that both Ni and nickel-copper alloy (NiCu) catalysts are good for hydrogenation of methyl levulinate (ML) to an intermediate species, 4-hydroxypentanoic acid (HPA). However, only NiCu has a better tendency to accelerate the conversion of HPA to GVL via cyclization process. Activation energy from experimental study of cyclization step over Ni is about two times larger than that of NiCu (E<inf>a</inf>K2 values are 121.7 and 56.0 kJ mol K−1 for Ni and NiCu, respectively) provided strong evidence of superior GVL production over NiCu catalyst. Density Functional Theory (DFT) simulation results reveal solid finding to support the high efficiency of NiCu over Ni catalyst for GVL production. The calculated energy barrier for HPA conversion to GVL over the NiCu is 1.0 eV which is lower than that of the Ni catalyst (1.54 eV). The Ni provided only one concerted pathway to transform from ML to GVL, while NiCu could provide either a concerted or nonconcerted pathway where the latter one requires lower activation energy for GVL production. The combination of these experimental and simulation results leads to a better understanding of bimetallic catalyst design for GVL production via catalytic transfer hydrogenation without any support materials.
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Simultaneous activation of copper mixed metal oxide catalysts in alcohols for gamma-valerolactone production from methyl levulinate
(2019-06-05)
Tanwongwan, Worapak
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Eiad-ua, Apiluck
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Kraithong, Wasawat
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Viriya-empikul, Nawin
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Suttisintong, Khomson
Catalytic transfer hydrogenation (CTH)of biomass-derivatives to value-added chemicals using metal-based catalysts is a promising process in biorefinery since it does not require high pressure of expensive and flammable hydrogen gas (H<inf>2</inf>). However, an activation of these catalysts using H<inf>2</inf> treatment prior to the CTH process limits this advantage. Here, copper mixed metal oxides are introduced as simultaneously activated catalysts (SACs)in the presence of alcohol for a production of gamma-valerolactone (GVL)from methyl levulinate (ML)without requirement of additional H<inf>2</inf> gas during both catalyst pretreatment and hydrogenation steps. Different alcohols were selected to function as hydrogen sources for both catalyst activation and ML hydrogenation. All copper mixed metal oxides, especially CuNiO showed significant potential as catalysts for ML conversion to GVL at 200 °C within 3 h. While 2-propanol and 2-butanol exhibited effective roles as hydrogen sources for simultaneous reductions of the catalysts to generate metal active sites and provided hydrogen species for hydrogenation of ML to GVL. Hydrogen temperature programmed reduction (H<inf>2</inf>-TPR), alcohol-assisted simultaneous reaction (ASR), in situ X-ray diffraction (in situ XRD)and X-ray photoelectron spectroscopy (XPS)revealed that the complementary cooperation between secondary alcohols and catalysts is the important key for the high GVL production in this work.
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Effects of thermal treatment on hydrophilicity and corrosion resistance of Ti surface
(2019-03-01)
Boonrungsiman, Suwimon
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Prompinit, Panida
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Khemthong, Pongtanawat
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Wutikhun, Tuksadon
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Treethong, Alongkot
Surface treatment of titanium (Ti) surface has been extensively studied to improve its properties for biomedical applications, including hydrophilicity, corrosion resistance, and tissue integration. In this present work, we present the effects of thermal oxidation as surface modification method on metallic titanium (Ti). The Ti foils were oxidized at 300°C, 400°C, 500°C, and 600°C under air atmosphere for 3 hours, which formed oxide layer on Ti surface. The physicochemical properties including surface chemistry, roughness, and thickness of the oxide layer were evaluated in order to investigate how these factors affected surface hydrophilicity, microhardness, and corrosion resistance properties of the Ti surface. The results revealed that surfaces of all oxidized samples were modified by formation of titanium dioxide layer, of which morphology, phase, and thickness were changed according to the oxidized temperatures. Increasing oxidation temperature led to the formation of thicker oxide layer and phase transformation of anatase to rutile. The presence of the oxide layer helped the improvement of corrosion resistance and microhardness. The most improvement in surface roughness was found in the specimens treated at 400°C, which significantly improved surface hydrophilicity. But both surface roughness and hydrophilicity reduced when oxidized at 500°C and 600°C, suggesting that hydrophilicity was dominated by the surface roughness. In addition, this surface treatment did not reduce the biocompatibility of the metallic Ti substrates against murine osteoblasts (MC3T3).
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Preparation and electrochemical performance of nitrogen-enriched activated carbon derived from silkworm pupae waste
(2019-01-01)
Sattayarut, Vichuda
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Chanthad, Chalathorn
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Khemthong, Pongtanawat
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Kuboon, Sanchai
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Wanchaem, Thanthamrong
In this study, nitrogen-enriched activated carbon from silkworm pupae waste (P-AC) was successfully prepared and its electrochemical performances in aqueous and organic electrolytes were investigated. Silkworm pupae waste is beneficial because it is a nitrogen-enriched, inexpensive, and locally available material. The preparation process includes hydrothermal treatment of the silkworm pupae waste at 200 °C, and chemical activation using zinc chloride at activation temperatures of 700, 800 and 900 °C (P700, P800, and P900, respectively). The nitrogen content in the P-ACs was approximately 3.8-6.4 at%, decreasing with activation temperature, while the surface area was approximately 1062-1267 m2 g-1, increasing with activation temperature. Compared to a commercial AC, the P-ACs show higher nitrogen content but lower surface area. Furthermore, the P800 exhibited superior specific capacitance (154.6 and 91.6 F g-1 in aqueous and organic electrolytes) compared to a commercial AC despite possessing smaller surface area. The high nitrogen content enhanced the pseudocapacitance and improved the electrical conductivity of the P-ACs. These properties were confirmed by relatively low series and charge transfer resistances, a capacity retention higher than 88% at a current density of 0.5 A g-1 and excellent cycling stability demonstrated by maintaining 97.6% of its capacitance after 3000 cycles. These results demonstrate that silkworm pupae waste is a viable source of nitrogen-enriched AC for application in supercapacitors.
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Texture orientation of silver thin films grown via gas-timing radio frequency magnetron sputtering and their SERS activity
(2016-01-01)
Ukahapunyakul, Pongbordin
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Gridsadanurak, Nurak
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Sapcharoenkun, Chaweewan
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Treetong, Alongkot
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Kasamechonchung, Panita
Here we demonstrate a special technique to control a texture orientation of silver (Ag) thin films using gas-timing (GT) rf magnetron sputtering. By utilizing a GT technique, a dense structure and a high ratio of (111)/(200) of Ag films could be obtained without applying additional energy sources. We found that the GT technique not only provides the ability to adjust the number of sputter species from the target, but also generates the self-energy assisted deposition which related to the atomic peening effect. Furthermore, we found that a high (111)/(200) ratio of Ag films strongly affects the SERS activity of the Ag films due to a hot spot effect. Our results highlight that the texture engineering of metal thin films could be accomplished by using a GT technique.
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