Polymers

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14 pages, 14440 KiB

Open AccessArticle

Sensitivity Enhancement of Acetone Gas Sensor using Polyethylene Glycol/Multi-Walled Carbon Nanotubes Composite Sensing Film with Thermal Treatment

by Jin-Chern Chiou, Chin-Cheng Wu and Tse-Mei Lin

Polymers 2019, 11(3), 423; https://doi.org/10.3390/polym11030423 - 5 Mar 2019

Cited by 17 | Viewed by 3927

Abstract

There is a need to develop a chemiresistive gas sensor equipped with a thermostat over a wide area for the sensor, which can protect the sensor from the influence of ambient temperature due to the uniform temperature of the thermostat. In this paper, [...] Read more.

There is a need to develop a chemiresistive gas sensor equipped with a thermostat over a wide area for the sensor, which can protect the sensor from the influence of ambient temperature due to the uniform temperature of the thermostat. In this paper, we demonstrated an acetone gas sensor based on a polyethylene glycol (PEG)/Multi-walled Carbon Nanotubes (MWCNTs) composite film, which was equipped with a thermostat. The sensor was operated at modest working temperatures for sensor sensitivity enhancement. The optimum design of the polyimide-based thermostat with widely uniform thermal distribution was investigated in detail. It was found that the temperature uniformity of the thermostat was achieved using double spiral geometry. The experimental results of the sensor response showed that the PEG/MWCNTs composite film with a moderate working temperature revealed a higher sensitivity than that without thermal treatment. Moreover, the sensing mechanisms of the PEG/MWCNTs composite gas sensor to acetone vapor were studied as well. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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16 pages, 6428 KiB

Open AccessEditor’s ChoiceArticle

High Response CO Sensor Based on a Polyaniline/SnO₂ Nanocomposite

by Kai-Syuan Jian, Chi-Jung Chang, Jerry J. Wu, Yu-Cheng Chang, Chien-Yie Tsay, Jing-Heng Chen, Tzyy-Leng Horng, Gang-Juan Lee, Lakshmanan Karuppasamy, Sambandam Anandan and Chin-Yi Chen

Polymers 2019, 11(1), 184; https://doi.org/10.3390/polym11010184 - 21 Jan 2019

Cited by 57 | Viewed by 6167

Abstract

A polyaniline (PANI)/tin oxide (SnO₂) composite for a CO sensor was fabricated using a composite film composed of SnO₂ nanoparticles and PANI deposition in the present study. Tin oxide nanoparticles were synthesized by the sol-gel method. The SnO₂ nanoparticles [...] Read more.

A polyaniline (PANI)/tin oxide (SnO₂) composite for a CO sensor was fabricated using a composite film composed of SnO₂ nanoparticles and PANI deposition in the present study. Tin oxide nanoparticles were synthesized by the sol-gel method. The SnO₂ nanoparticles provided a high surface area to significantly enhance the response to the change in CO concentration at low operating temperature (<75 °C). The excellent sensor response was mainly attributed to the relatively good properties of PANI in the redox reaction during sensing, which produced a great resistance difference between the air and CO gas at low operating temperature. Therefore, the combination of n-type SnO₂ nanoparticles with a high surface area and a thick film of conductive PANI is an effective strategy to design a high-performance CO gas sensor. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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14 pages, 2389 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Dye and Cr^(VI) Degradation Using a Metal-Free Polymeric g-C₃N₄ Synthesized from Solvent-Treated Urea

by Chechia Hu, Yi-Ching Chu, Yan-Ru Lin, Hung-Chun Yang and Ke-Hsuan Wang

Polymers 2019, 11(1), 182; https://doi.org/10.3390/polym11010182 - 21 Jan 2019

Cited by 38 | Viewed by 7323

Abstract

The development of visible-light-driven polymeric g-C₃N₄ is in response to an emerging demand for the photocatalytic dye degradation and reduction of hexavalent chromium ions. We report the synthesis of g-C₃N₄ from urea treated with various solvents such [...] Read more.

The development of visible-light-driven polymeric g-C₃N₄ is in response to an emerging demand for the photocatalytic dye degradation and reduction of hexavalent chromium ions. We report the synthesis of g-C₃N₄ from urea treated with various solvents such as methanol, ethanol, and ethylene glycol. The samples were characterized and the Williamson–Hall method was applied to investigate the lattice strain of the samples. The activity of the samples was evaluated by observing the degradation of methyl orange and K₂Cr₂O₇ solution under light irradiation. Photocatalytic reaction kinetics were determined as pseudo-first-order and zero-order for the degradation of methyl orange and reduction of hexavalent chromium, respectively. Due to the inhibited charge separation resulting from the small lattice strain, reduced crystal imperfection, and sheet-like structure, g-C₃N₄ obtained from ethanol-treated urea exhibited the highest activity among the evaluated samples. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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16 pages, 4885 KiB

Open AccessArticle

Anatase TiO₂-Decorated Graphitic Carbon Nitride for Photocatalytic Conversion of Carbon Dioxide

by I-Hsiang Tseng, Yu-Min Sung, Po-Ya Chang and Chin-Yi Chen

Polymers 2019, 11(1), 146; https://doi.org/10.3390/polym11010146 - 16 Jan 2019

Cited by 29 | Viewed by 6727

Abstract

Three types of graphitic carbon nitride (gCN) nanosheets were derived from direct thermal condensation of urea, melamine, and dicyandiamide, respectively. As the sample (uCN) synthesized from urea exhibited porous morphology and highest surface area among other gCN, anatase TiO₂ nanoparticles were then [...] Read more.

Three types of graphitic carbon nitride (gCN) nanosheets were derived from direct thermal condensation of urea, melamine, and dicyandiamide, respectively. As the sample (uCN) synthesized from urea exhibited porous morphology and highest surface area among other gCN, anatase TiO₂ nanoparticles were then in-situ deposited on uCN via solvothermal process without further calcination. The resultant Ti/uCN_x samples remained with higher surface area and exhibited visible-light activity. The derived band structure of each sample also confirmed its ability to photoreduce CO₂. XPS results revealed surface compositions of each sample. Those functional groups governed adsorption of reactant, interfacial interaction, electron transfer rate, and consequently influenced the yield of products. Carbon monoxide and methanol were detected from LED-lamp illuminated samples under appropriate moisture content. Samples with higher ratio of terminal amine groups produced more CO. The presence of hydroxyl groups promoted the initial conversion of methanol. The obtained Ti/uCN_0.5 and Ti/uCN_1.5 samples exhibited better quantum efficiency toward CO₂ conversion and demonstrated stability to consistently produce CO under cycling photoreaction. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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14 pages, 4338 KiB

Open AccessArticle

The Ternary Heterostructures of BiOBr/Ultrathin g-C₃N₄/Black Phosphorous Quantum Dot Composites for Photodegradation of Tetracycline

by Tianhao Jiang, Chaoqun Shang, Qingguo Meng, Mingliang Jin, Hua Liao, Ming Li, Zhihong Chen, Mingzhe Yuan, Xin Wang and Guofu Zhou

Polymers 2018, 10(10), 1118; https://doi.org/10.3390/polym10101118 - 9 Oct 2018

Cited by 11 | Viewed by 4535

Abstract

Herein, we synthesized BiOBr/ultrathin g-C₃N₄/ternary heterostructures modified with black phosphorous quantum dots using a simple water bath heating and sonication method. The ternary heterostructure was then used for the photocatalytic degradation of tetracycline in visible light, with an efficiency [...] Read more.

Herein, we synthesized BiOBr/ultrathin g-C₃N₄/ternary heterostructures modified with black phosphorous quantum dots using a simple water bath heating and sonication method. The ternary heterostructure was then used for the photocatalytic degradation of tetracycline in visible light, with an efficiency as high as 92% after 3 h of irradiation. Thus, the photodegradation efficiency is greatly improved compared to that of ultrathin g-C₃N₄, BiOBr, and black phosphorous quantum dots alone. The synthesized ternary heterostructure improves the charge separation efficiency, thus increasing the photodegradation efficiency. This work provides a new and efficient method for the degradation of antibiotics in the environment. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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10 pages, 3335 KiB

Open AccessArticle

Enhancement of Rhodamine B Degradation by Ag Nanoclusters-Loaded g-C₃N₄ Nanosheets

by Thi Mai Oanh Le, Thi Hang Lam, Thi Nhung Pham, Tuan Cuong Ngo, Ngoc Diep Lai, Danh Bich Do and Van Minh Nguyen

Polymers 2018, 10(6), 633; https://doi.org/10.3390/polym10060633 - 8 Jun 2018

Cited by 25 | Viewed by 6045

Abstract

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) [...] Read more.

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) rather than well-crystallized nanoparticles are evidenced by X-ray diffraction patterns, SEM images, and XPS spectra. The deposition of Ag nanoclusters on the surface of g-C₃N₄ nanosheets affect the crystal structure and slightly reduce the band gap energy of g-C₃N₄. The sharp decrease of photoluminescence intensity indicates that g-C₃N₄/Ag heterojunctions successfully prevent the recombination of photo-generated electrons and holes. The photocatalytic activities of as-synthesized photocatalysts are demonstrated through the degradation of rhodamine B (RhB) solutions under Xenon lamp irradiation. It is demonstrated that the photocatalytic activity depends strongly on the molar concentration of Ag⁺ in the starting solution. The g-C₃N₄/Ag heterojunctions prepared from 0.01 M of Ag⁺ starting solution exhibit the highest photocatalytic efficiency and allow 100% degradation of RhB after being exposed for 60 min under a Xenon lamp irradiation, which is four times faster than that of pure g-C₃N₄ nanosheets. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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Review

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31 pages, 3803 KiB

Open AccessEditor’s ChoiceReview

Recent Progress of Carbon Dot Precursors and Photocatalysis Applications

by Kuan-Wu Chu, Sher Ling Lee, Chi-Jung Chang and Lingyun Liu

Polymers 2019, 11(4), 689; https://doi.org/10.3390/polym11040689 - 16 Apr 2019

Cited by 145 | Viewed by 13848

Abstract

Carbon dots (CDs), a class of carbon-based sub-ten-nanometer nanoparticles, have attracted great attention since their discovery fifteen years ago. Because of the outstanding photoluminescence properties, photostability, low toxicity, and low cost, CDs have potential to replace traditional semiconductor quantum dots which have serious [...] Read more.

Carbon dots (CDs), a class of carbon-based sub-ten-nanometer nanoparticles, have attracted great attention since their discovery fifteen years ago. Because of the outstanding photoluminescence properties, photostability, low toxicity, and low cost, CDs have potential to replace traditional semiconductor quantum dots which have serious drawbacks of toxicity and high cost. This review covers the common top-down and bottom-up methods for the synthesis of CDs, different categories of CD precursors (small molecules, natural polymers, and synthetic polymers), one-pot and multi-step methods to produce CDs/photocatalyst composites, and recent advances of CDs on photocatalysis applications mostly in pollutant degradation and energy areas. A broad range of precursors forming fluorescent CDs are discussed, including small molecule sole or dual precursors, natural polymers such as pure polysaccharides and proteins and crude bio-resources from plants or animals, and various synthetic polymer precursors with positive, negative, neutral and hydrophilic, hydrophobic, or zwitterionic feature. Because of the wide light absorbance, excellent photoluminescence properties and electron transfer ability, CDs have emerged as a new type of photocatalyst. Recent work of CDs as sole photocatalyst or in combination with other materials (e.g., metal, metal sulfide, metal oxide, bismuth-based semiconductor, or other traditional photocatalysts) to form composite catalyst for various photocatalytic applications are reviewed. Possible future directions are proposed at the end of the article on mechanistic studies, production of CDs with better controlled properties, expansion of polymer precursor pool, and systematic studies of CDs for photocatalysis applications. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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21 pages, 3112 KiB

Open AccessEditor’s ChoiceReview

Recent Developments about Conductive Polymer Based Composite Photocatalysts

by Sher Ling Lee and Chi-Jung Chang

Polymers 2019, 11(2), 206; https://doi.org/10.3390/polym11020206 - 24 Jan 2019

Cited by 142 | Viewed by 10774

Abstract

Conductive polymers have been widely investigated in various applications. Several conductive polymers, such as polyaniline (PANI), polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT)), and polythiophene (PTh) have been loaded with various semiconductor nanomaterials to prepare the composite photocatalysts. However, a critical review of conductive polymer-based composite [...] Read more.

Conductive polymers have been widely investigated in various applications. Several conductive polymers, such as polyaniline (PANI), polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT)), and polythiophene (PTh) have been loaded with various semiconductor nanomaterials to prepare the composite photocatalysts. However, a critical review of conductive polymer-based composite photocatalysts has not been available yet. Therefore, in this review, we summarized the applications of conductive polymers in the preparation of composite photocatalysts for photocatalytic degradation of hazardous chemicals, antibacterial, and photocatalytic hydrogen production. Various materials were systematically surveyed to illustrate their preparation methods, morphologies, and photocatalytic performances. The synergic effect between conductive polymers and semiconductor nanomaterials were observed for a lot of composite photocatalysts. The band structures of the composite photocatalysts can be analyzed to explain the mechanism of their enhanced photocatalytic activity. The incorporation of conductive polymers can result in significantly improved visible-light driven photocatalytic activity by enhancing the separation of photoexcited charge carriers, extending the light absorption range, increasing the adsorption of reactants, inhibiting photo-corrosion, and reducing the formation of large aggregates. This review provides a systematic concept about how conductive polymers can improve the performance of composite photocatalysts. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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