Chemistry of 2D Materials

Topic Information

Dear Colleagues,

Since the ground-breaking experiment on graphene in 2004, 2D materials have attracted enormous attention among researchers from the chemistry, physics, materials science and engineering, medicine, and industrial sectors. Two-dimensional materials possess outstanding chemical and physical properties and hold many potential applications in electronic and optoelectronic devices, energy conversion and storage, biological engineering, nanocomposites, and membranes. Intensive research has stimulated the generation of various types of 2D semiconductors, semimetals, metals, and insulators, such as phosphorene, boron nitride, transition metal dichalcogenides, transition metal oxides/hydroxides, transition metal carbides and carbonitrides, 2D polymers, etc.

Chemical approaches have been proven to be a promising route towards the large-scale production of 2D materials and their derivatives. This Special Issue aims to focus on the various chemical strategies for 2D materials; the topics include but are not limited to:

• Preparation and synthesis of 2D materials;
• Chemical modification of 2D materials;
• Characterization of 2D materials and functionalized 2D materials;
• Properties of 2D materials and functionalized 2D materials;
• Applications of 2D materials and functionalized 2D materials.

Dr. Xiaoyan Zhang
Dr. Raul Arenal
Prof. Dr. Yafei Li
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Chemistry chemistry	2.4	3.2	2019	13.4 Days	CHF 1800
Materials materials	3.1	5.8	2008	15.5 Days	CHF 2600
Molecules molecules	4.2	7.4	1996	15.1 Days	CHF 2700
Nanomaterials nanomaterials	4.4	8.5	2010	13.8 Days	CHF 2900
Sensors sensors	3.4	7.3	2001	16.8 Days	CHF 2600

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Published Papers (7 papers)

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21 pages, 3729 KiB  

Open AccessArticle

Composition Effect on the Formation of Oxide Phases by Thermal Decomposition of CuNiM(III) Layered Double Hydroxides with M(III) = Al, Fe

by Iqra Zubair Awan, Phuoc Hoang Ho, Giada Beltrami, Bernard Fraisse, Thomas Cacciaguerra, Pierrick Gaudin, Nathalie Tanchoux, Stefania Albonetti, Annalisa Martucci, Fabrizio Cavani, Francesco Di Renzo and Didier Tichit

Materials 2024, 17(1), 83; https://doi.org/10.3390/ma17010083 - 23 Dec 2023

Viewed by 1244

Abstract

The thermal decomposition processes of coprecipitated Cu-Ni-Al and Cu-Ni-Fe hydroxides and the formation of the mixed oxide phases were followed by thermogravimetry and derivative thermogravimetry analysis (TG – DTG) and in situ X-ray diffraction (XRD) in a temperature range from 25 to 800 [...] Read more.

The thermal decomposition processes of coprecipitated Cu-Ni-Al and Cu-Ni-Fe hydroxides and the formation of the mixed oxide phases were followed by thermogravimetry and derivative thermogravimetry analysis (TG – DTG) and in situ X-ray diffraction (XRD) in a temperature range from 25 to 800 °C. The as-prepared samples exhibited layered double hydroxide (LDH) with a rhombohedral structure for the Ni-richer Al- and Fe-bearing LDHs and a monoclinic structure for the CuAl LDH. Direct precipitation of CuO was also observed for the Cu-richest Fe-bearing samples. After the collapse of the LDHs, dehydration, dehydroxylation, and decarbonation occurred with an overlapping of these events to an extent, depending on the structure and composition, being more pronounced for the Fe-bearing rhombohedral LDHs and the monoclinic LDH. The Fe-bearing amorphous phases showed higher reactivity than the Al-bearing ones toward the crystallization of the mixed oxide phases. This reactivity was improved as the amount of embedded divalent cations increased. Moreover, the influence of copper was effective at a lower content than that of nickel. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Full article ">Figure 1
<p>XRD patterns for as-synthesized (Cu,Ni)Al samples. Indexed peaks: M, monoclinic and T, trigonal LDHs, CuO tenorite, Δ: PtRh powder support.</p> Full article ">Figure 2
<p>TG (<b>A</b>) and DTG (<b>B</b>) curves of the (Cu,Ni)Al samples.</p> Full article ">Figure 3
<p>XRD patterns of sample Cu75Al25 at room temperature and 100 °C.</p> Full article ">Figure 4
<p>XRD patterns of Ni75Al25 (<b>A</b>), Cu38Ni37Al25 (<b>B</b>), and Cu75Al25 (<b>C</b>) at 400 (a), 600 (b) and 800 °C (c). ?: unknown (see text). Indexed peaks: NiO bunsenite, CuO tenorite, spinel, Δ: PtRh powder support.</p> Full article ">Figure 5
<p>XRD patterns of as-synthesized (Cu,Ni)Fe samples. Indexed peaks: T, trigonal LDH, CuO tenorite, Δ: PtRh powder support.</p> Full article ">Figure 6
<p>TG (<b>A</b>) and DTG (<b>B</b>) curves of (Cu,Ni)Fe samples. The DTG curves are shifted for the sake of clarity.</p> Full article ">Figure 7
<p>XRD patterns of Ni75Fe25 (<b>A</b>), Cu38Ni37Fe25 (<b>B</b>), and Cu75Fe25 (<b>C</b>) at 400 (a), 600 (b), and 800 (c) °C. Indexed peaks: NiO bunsenite, CuO tenorite, spinel, Δ: PtRh powder support.</p> Full article ">Figure 8
<p>Comparison of the DTG curves of Al-bearing (red traces) and Fe-bearing (green traces) samples with Cu/(Cu + Ni) = y = 0 (<b>A</b>) or 0.5 (<b>B</b>). DTGn labels as in <a href="#materials-17-00083-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 9
<p>Comparison of experimental and theoretical mass losses in DTG₁ (<b>A</b>), DTG₂ (<b>B</b>), and DTG₃ + DTG₄ (<b>C</b>) steps from <a href="#materials-17-00083-t003" class="html-table">Table 3</a> for Al-bearing (void squares) and Fe-bearing (green triangles) samples. Samples Ni75Al25 (a), Cu08Ni67Al25 (b), Cu38Ni37Al25 (c), Cu75Al25 (d), Ni75Fe25 (e), Cu07Ni68Fe25 (f), and Cu38Ni37Fe25 (g). A red arrow highlights monoclinic Cu75Al25.</p> Full article ">Figure 10
<p>Mass % of phases in samples of the series (Cu,Ni)Al (<b>top</b>) and (Cu,Ni)Fe (<b>bottom</b>) as a function of temperature in XRD thermal ramp: NiO bunsenite (green), CuO tenorite (red), and spinel (blue).</p> Full article ">

14 pages, 2991 KiB  

Open AccessArticle

The Green Synthesis of Reduced Graphene Oxide Using Ellagic Acid: Improving the Contrast-Enhancing Effect of Microbubbles in Ultrasound

by Qiwei Cheng, Yuzhou Wang, Qi Zhou, Shaobo Duan, Beibei Zhang, Yaqiong Li and Lianzhong Zhang

Molecules 2023, 28(22), 7646; https://doi.org/10.3390/molecules28227646 - 17 Nov 2023

Viewed by 1878

Abstract

There is an urgent need to realize precise clinical ultrasound with ultrasound contrast agents that provide high echo intensity and mechanical index tolerance. Graphene derivatives possess exceptional characteristics, exhibiting great potential in fabricating ideal ultrasound contrast agents. Herein, we reported a facile and [...] Read more.

There is an urgent need to realize precise clinical ultrasound with ultrasound contrast agents that provide high echo intensity and mechanical index tolerance. Graphene derivatives possess exceptional characteristics, exhibiting great potential in fabricating ideal ultrasound contrast agents. Herein, we reported a facile and green approach to synthesizing reduced graphene oxide with ellagic acid (rGO-EA). To investigate the application of a graphene derivative in ultrasound contrast agents, rGO-EA was dispersed in saline solution and mixed with SonoVue (SV) to fabricate SV@rGO-EA microbubbles. To determine the properties of the product, analyses were performed, including ultraviolet–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectrum (XPS), X-ray diffraction analysis (XRD) and zeta potential analysis. Additionally, cell viability measurements and a hemolysis assay were conducted for a biosafety evaluation. SV@rGO-EA microbubbles were scanned at various mechanical index values to obtain the B-mode and contrast-enhanced ultrasound (CEUS) mode images in vitro. SV@rGO-EA microbubbles were administered to SD rats, and their livers and kidneys were imaged in CEUS and B-mode. The absorption of rGO-EA resulted in an enhanced echo intensity and mechanical index tolerance of SV@rGO-EA, surpassing the performance of SV microbubbles both in vitro and in vivo. This work exhibited the application potential of graphene derivatives in the field of ultrasound precision medicine. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Full article ">Figure 1
<p>The UV–vis (<b>a</b>), FTIR (<b>b</b>), Raman (<b>c</b>) and XRD (<b>d</b>) spectra of GO and rGO-EA.</p> Full article ">Figure 2
<p>(<b>a</b>)The TGA curves of GO, EA and rGO-EA. The mass losses were observed between 40 °C and 800 °C. (<b>b</b>) Zeta potential of GO and rGO-EA was determined at 25 °C (<span class="html-italic">n</span> = 5).</p> Full article ">Figure 3
<p>The XPS survey spectra of GO (<b>a</b>) and rGO-EA (<b>c</b>). The deconvoluted C 1s spectra of GO (<b>b</b>) and rGO-EA (<b>d</b>).</p> Full article ">Figure 4
<p>TEM images of GO (<b>a</b>) and rGO-EA (<b>b</b>) with the SAED pattern inset.</p> Full article ">Figure 5
<p>The cell viability of NIH3T3 and 4T1 cells treated with rGO-EA. Group A: NIH3T3 cells. Group B: 4T1 cells. The concentration of rGO-EA varied from 3.125 to 200 μg/mL. Cells incubated in complete medium were set as a control. *: <span class="html-italic">p</span> &lt; 0.05 between NIH3T3 and 4T1 groups (<span class="html-italic">n</span> = 6).</p> Full article ">Figure 6
<p>The hemolysis of RBCs incubated with rGO-EA for 4h at 37 °C. *: <span class="html-italic">p</span> &lt; 0.05 compared with other groups, in which the arrow pointed to (<span class="html-italic">n</span> = 5).</p> Full article ">Figure 7
<p>(<b>a</b>) TEM images of SV. SV MBs displayed spherical surfaces. (<b>b</b>) TEM images of SV@rGO-EA. rGO-EA could be clearly seen on the surface of SV. (<b>c</b>) Zeta potential values of SV and SV@rGO-EA were measured at 25 °C (<span class="html-italic">n</span> = 5).</p> Full article ">Figure 8
<p>(<b>a</b>) The CEUS and B-mode ultrasound images of contrast agents in vitro. (<b>b</b>) Echo intensities of groups in conditions of different MIs. Group A: control, which contained SV only. Groups B–D: SV@rGO-EA groups, where the concentrations of rGO-EA were 0.05, 0.10 and 0.20 mg/mL, respectively. *: <span class="html-italic">p</span> &lt; 0.05 compared with the SV group (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 9
<p>CEUS and B-mode US images of SV MBs in the liver (<b>a</b>) and kidney (<b>c</b>). CEUS and B-mode US images of SV@rGO-EA MBs in the liver (<b>b</b>) and kidney (<b>d</b>). Images were acquired after the intravenous injection at 5 s, 10 s and 30 s, respectively. The concentration of rGO-EA in SV@rGO-EA MBs was 0.10 mg/mL. The equivalent SV concentration was 5 mg/mL. The MI value was 0.08.</p> Full article ">Figure 10
<p>(<b>a</b>) Quantitative analysis of the mean echo intensity in the drawn ROIs in SD rat livers after injection. (<b>b</b>) Quantitative analysis of the mean echo intensity in the drawn ROIs in SD rat kidneys after injection. The echo intensity in ROI, the rectangle with the area of about 1 mm², accepted quantitative analysis by the data analysis software QLAB10. Group A: tail intravenous injection of SV was set as a control. Group B: tail intravenous injection of SV@rGO-EA. SV concentration in each group was 5 mg/mL. The rGO-EA concentration in SV@rGO-EA MBs was 0.10 mg/mL. The MI value was 0.08. *: <span class="html-italic">p</span> &lt; 0.05 compared with each group (<span class="html-italic">n</span> = 6).</p> Full article ">

24 pages, 1558 KiB  

Open AccessReview

Two-Dimensional Materials: From Discovery to Application in Membrane Distillation/Crystallization Processes

by Mirko Frappa, Francesca Alessandro, Francesca Macedonio and Enrico Drioli

Chemistry 2023, 5(4), 2205-2228; https://doi.org/10.3390/chemistry5040148 - 16 Oct 2023

Viewed by 1743

Abstract

Sustainable water desalination and purification membrane processes require new practical pathways to improve their efficiency. To this end, the inclusion of two-dimensional materials in membrane structure has proven to have a significant impact in various applications. In particular, in processes such as membrane [...] Read more.

Sustainable water desalination and purification membrane processes require new practical pathways to improve their efficiency. To this end, the inclusion of two-dimensional materials in membrane structure has proven to have a significant impact in various applications. In particular, in processes such as membrane distillation and crystallization, these materials, thanks to their characteristics, help to increase the recovery of clean water and, at the same time, to improve the quality and the production of the recovered salts. Therefore, a fundamental aspect of obtaining 2D materials with certain characteristics is the technique used for the preparation. This review provides a broad discussion on the preparation and proprieties of 2D materials, including examples of organic structures (such as graphene and structures containing transition metals and organic metals). Finally, the critical challenges, future research directions, and the opportunities for developing advanced membranes based on 2D materials are outlined. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Full article ">Figure 1
<p>Top-down and bottom-up approaches for materials exfoliation.</p> Full article ">Figure 2
<p>Main exfoliation methods used for the graphene production.</p> Full article ">Figure 3
<p>Trans-membrane flux of graphene-based membrane in DCMD.</p> Full article ">

14 pages, 4783 KiB  

Open AccessFeature PaperArticle

Label-Free Homogeneous Electrochemical Aptasensor Based on Size Exclusion/Charge-Selective Permeability of Nanochannel Arrays and 2D Nanorecognitive Probe for Sensitive Detection of Alpha-Fetoprotein

by Yue Zhang, Shiyue Zhang, Jiyang Liu and Dongyuan Qin

Molecules 2023, 28(19), 6935; https://doi.org/10.3390/molecules28196935 - 5 Oct 2023

Cited by 10 | Viewed by 1340

Abstract

The labeling-free and immobilization-free homogeneous aptamer sensor offers advantages including simple operation, low cost, and high sensitivity, demonstrating great potential in rapid detection of tumor biomarkers in biological samples. In this work, a labeling-free and immobilization-free homogeneous aptamer sensor was conveniently fabricated by [...] Read more.

The labeling-free and immobilization-free homogeneous aptamer sensor offers advantages including simple operation, low cost, and high sensitivity, demonstrating great potential in rapid detection of tumor biomarkers in biological samples. In this work, a labeling-free and immobilization-free homogeneous aptamer sensor was conveniently fabricated by combining size exclusion and charge-selective penetration of a nanochannel-modified electrode and two-dimensional (2D) nanorecognition probe which can realize selective and highly sensitive detection of alpha-fetoprotein (AFP) in serum. Vertically ordered mesoporous silica film (VMSF) with ultra-small, uniform, and vertically aligned nanochannels was easily grown on the simple, low-cost, and disposable indium tin oxide (ITO) electrode. Through π-π interaction and electrostatic force, the AFP aptamer (Apt) and electrochemical probe, tris(bipyridine)ruthenium(II) (Ru(bpy)₃²⁺), were coloaded onto graphene oxide (GO) through simple incubation, forming a 2D nanoscale recognition probe (Ru(bpy)₃²⁺/Apt@GO). Owing to the size exclusion effect of VMSF towards the 2D nanoscale probe, the electrochemical signal of Ru(bpy)₃²⁺/Apt@GO could not be detected. In the presence of AFP, the specific binding of AFP to the aptamer causes the dissociation of the aptamer and Ru(bpy)₃²⁺ from GO, resulting in their presence in the solution. The efficient electrostatic enrichment towards Ru(bpy)₃²⁺ by negatively charged VMSF allows for high electrochemical signals of free Ru(bpy)₃²⁺ in the solution. Linear determination of AFP ranged from 1 pg/mL to 1000 ng/mL and could be obtained with a low limit of detection (LOD, 0.8 pg/mL). The high specificity of the adapter endowed the constructed sensor with high selectivity. The fabricated probe can be applied in direct determination of AFP in serum. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Figure 1
<p>Illustration of the fabrication of labeling-free and immobilization-free homogeneous electrochemical aptasensor for detecting AFP by integrating nanoscale recognition probes with nanochannel array-modified electrode. The left panel shows the preparation of nanoscale recognition probe and its binding to AFP. The right panel illustrates the fabrication of VMSF/ITO electrode and the process of AFP detection.</p> Full article ">Figure 2
<p>(<b>a</b>) TEM image of surface of VMSF. Inset is the corresponding high-resolution TEM image. The circled portion represents a hexagonal structure formed by the arrangement of the nanochannels. (<b>b</b>) Cross-sectional SEM of VMSF/ITO electrode. (<b>c</b>,<b>d</b>) CV curves measured using different electrodes in KHP (50 mM, pH = 4) + Fe(CN)₆³⁻ (0.5 mM, (<b>c</b>)) or Ru(NH₃)₆³⁺ (0.5 mM, (<b>d</b>)). Scan rate is 100 mV/s.</p> Full article ">Figure 3
<p>(<b>a</b>) UV-Vis absorption spectrum of GO. (<b>b</b>) High-resolution C1s spectrum of GO. (<b>c</b>) FTIR spectrum of GO. (<b>d</b>) TEM image of GO.</p> Full article ">Figure 3 Cont.
<p>(<b>a</b>) UV-Vis absorption spectrum of GO. (<b>b</b>) High-resolution C1s spectrum of GO. (<b>c</b>) FTIR spectrum of GO. (<b>d</b>) TEM image of GO.</p> Full article ">Figure 4
<p>(<b>a</b>) The zeta potential of nanomaterials in different incubation solutions. (<b>b</b>) DPV curves obtained on ITO or VMSF/ITO electrode in Ru(bpy)₃²⁺, Ru(bpy)₃²⁺/Apt@GO nanoprobe in absence or presence of AFP.</p> Full article ">Figure 5
<p>(<b>a</b>) DPV curves for detecting different concentrations of AFP using the constructed homogeneous aptamer sensor. (<b>b</b>) The corresponding linear calibration curve.</p> Full article ">Figure 6
<p>(<b>a</b>) The DPV signal difference (<span class="html-italic">I</span>-<span class="html-italic">I</span>₀) before (<span class="html-italic">I</span>₀) and after (<span class="html-italic">I</span>) Ru(bpy)₃²⁺/Apt@GO incubates with CEA (0.1 ng/mL), PSA (0.1 ng/mL), NGAL (0.1 ng/mL), Glu (10 μM), AFP (0.1 ng/mL), or their mixture. (<b>b</b>) The Bland–Altman scatter plot in Bland–Altman analysis of the detection results obtained using the fabricated homogenous aptamer sensor and Roche ECL analyzer.</p> Full article ">

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Supplementary material:
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12 pages, 3626 KiB  

Open AccessArticle

Single-Layer GaInSe₃: Promising Water-Splitting Photocatalyst with Solar Conversion Efficiency over 30% from Theoretical Calculations

by Li-Li Liu, Ru-Fei Tang, De-Fen Li, Ming-Xia Tang, Bing-Zhong Mu, Zheng-Quan Hu, Shi-Fa Wang, Yu-Feng Wen and Xiao-Zhi Wu

Molecules 2023, 28(19), 6858; https://doi.org/10.3390/molecules28196858 - 28 Sep 2023

Cited by 2 | Viewed by 1204

Abstract

Hydrogen energy from solar water-splitting is known as an ideal method with which to address the energy crisis and global environmental pollution. Herein, the first-principles calculations are carried out to study the photocatalytic water-splitting performance of single-layer GaInSe₃ under biaxial strains from [...] Read more.

Hydrogen energy from solar water-splitting is known as an ideal method with which to address the energy crisis and global environmental pollution. Herein, the first-principles calculations are carried out to study the photocatalytic water-splitting performance of single-layer GaInSe₃ under biaxial strains from −2% to +2%. Calculations reveal that single-layer GaInSe₃ under various biaxial strains has electronic bandgaps ranging from 1.11 to 1.28 eV under biaxial strain from −2% to +2%, as well as a completely separated valence band maximum and conduction band minimum. Meanwhile, the appropriate band edges for water-splitting and visible optical absorption up to ~3 × 10⁵ cm⁻¹ are obtained under biaxial strains from −2% to 0%. More impressively, the solar conversion efficiency of single-layer GaInSe₃ under biaxial strains from −2% to 0% reaches over 30%. The OER of unstrained single-layer GaInSe₃ can proceed without co-catalysts. These demonstrate that single-layer GaInSe₃ is a viable material for solar water-splitting. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) The top and side views, where the rhombus denotes the primitive cell and the rectangle represents the orthogonal supercell. (<b>b</b>) The vacuum level difference of unstrained single-layer GaInSe₃, where the inset is the charge distribution of CBM (red) and VBM (blue). The red dashed horizontal lines are auxiliary lines. The solid blue curve shows the change in vacuum level.</p> Full article ">Figure 2
<p>The electronic band structure (<b>Left</b>) and water-splitting property (<b>Right</b>) of single-layer GaInSe₃ under biaxial strains of (<b>a</b>) −2%, (<b>b</b>) −1%, (<b>c</b>) 0%, and (<b>d</b>) +1% obtained via HSE06. The upper and lower red columns denote the CBM and the VBM, respectively. The blue and red lines represent the redox potentials of H⁺/H₂ and H₂O/O₂, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) Frequency-dependent absorption coefficients of single-layer GaInSe₃ under biaxial strains of −2%, −1%, and 0% by G₀W₀-BSE. (<b>b</b>) Transition dipole moment of single-layer GaInSe₃ under biaxial strains of −2%, −1%, and 0% by HSE06.</p> Full article ">Figure 4
<p>(<b>a</b>) The Gibbs free energy change of OER on the Se atomic plane; (<b>b</b>) that of HER on the bottom Ga atomic layer of unstrained single-layer GaInSe₃ at pH = 0. The * indicates the adsorbed material.</p> Full article ">

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Supplementary material:
Supplementary File 1 (ZIP, 698 KiB)

13 pages, 9839 KiB  

Open AccessArticle

Enabling Quick Response to Nitrogen Dioxide at Room Temperature and Limit of Detection to Ppb Level by Heavily n-Doped Graphene Hybrid Transistor

by Si-Wei Song, Qian-Min Wang, Miao Yu, Zhi-Yuan Tian and Zhi-Yong Yang

Molecules 2023, 28(13), 5054; https://doi.org/10.3390/molecules28135054 - 28 Jun 2023

Viewed by 1110

Abstract

Sensitive detection of nitrogen dioxide (NO₂) is of significance in many areas for health and environmental protections. In this work, we developed an efficient NO₂ sensor that can respond within seconds at room temperature, and the limit of detection (LOD) [...] Read more.

Sensitive detection of nitrogen dioxide (NO₂) is of significance in many areas for health and environmental protections. In this work, we developed an efficient NO₂ sensor that can respond within seconds at room temperature, and the limit of detection (LOD) is as low as 100 ppb. Coating cyano-substituted poly(p-phenylene vinylene) (CN-PPV) films on graphene (G) layers can dope G sheets effectively to a heavy n state. The influences of solution concentrations and annealing temperatures on the n-doping effect were investigated in detail. The CN-PPV–G transistors fabricated with the optimized parameters demonstrate active sensing abilities toward NO₂. The n-doping state of CN-PPV–G is reduced dramatically by NO₂, which is a strong p-doping compound. Upon exposure to 25 ppm of NO₂, our CN-PPV–G sensors react in 10 s, indicating it is almost an immediate response. LOD is determined as low as 100 ppb. The ultrahigh responding speed and low LOD are not affected in dry air. Furthermore, cycling use of our sensors can be realized through simple annealing. The superior features shown by our CN-PPV–G sensors are highly desired in the applications of monitoring the level of NO₂ in situ and setting immediate alarms. Our results also suggest that transfer curves of transistors can react very promptly to the stimulus of target gas and, thus, are very promising in the development of fast-response sensing devices although the response values may not reach maximum as a tradeoff. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Figure 1
<p>(<b>a</b>) Raman spectroscopy of G sheets; (<b>b</b>) illustration of chemical structure of CN-PPV.</p> Full article ">Figure 2
<p>AFM topography images of CN-PPV–G films prepared with the solution of 5 mg mL⁻¹ before and after 1 h thermal annealing at 373 K, 393 K and 423 K.</p> Full article ">Figure 3
<p>SEM images of CN-PPV–G films prepared with the solution of 5 mg mL⁻¹ before and after 1 h thermal annealing at 373 K, 393 K and 423 K. Contrast and brightness of zoom-in images were post adjusted to clearly show the topographical target, which is not easily recognized in the small-size original micrographs.</p> Full article ">Figure 4
<p>(<b>a</b>,<b>b</b>) GIWAXS patterns collected on CN-PPV–G films prepared from 5 mg mL⁻¹ before and after annealed 1 h at 423 K, respectively. The first dot in the <span class="html-italic">z</span> direction of each image is not a signal that can be reasonably generated by our CN-PPV–G films, so we discarded the corresponding peak in the fitting profiles (<a href="#app1-molecules-28-05054" class="html-app">Figure S4</a>).</p> Full article ">Figure 5
<p>Transfer curves (V_ds = 1 V) of pristine G and CN-PPV–G samples casted from different concentrations before (<b>a</b>) and after annealing 1 h at 373 K (<b>b</b>), 393 K (<b>c</b>) and 423 K (<b>d</b>).</p> Full article ">Figure 6
<p>(<b>a</b>) Summarized V_g of MP on the transfer curves and (<b>b</b>) E_f (related to the MP position) of pristine G and CN-PPV–G samples casted from different concentrations before and after annealing 1 h at different temperatures. The dashed line in (<b>a</b>,<b>b</b>) indicates the V_g = 0 and energy level of MP (set as reference point of E_f), respectively. RT is around 298 K.</p> Full article ">Figure 7
<p>I_ds (<b>a</b>, V_ds = 1 V), I_sensing (<b>b</b>) and (<b>c</b>) R-V_g curves of CN-PPV–G transistors to 50 ppm NO₂ in N₂ environment; R-V_g curves of CN-PPV–G transistors to 25 ppm (<b>d</b>), 1 ppm (<b>e</b>) and 100 ppb (<b>f</b>) NO₂ in N₂ environment. 0 s means before NO₂ exposure.</p> Full article ">Figure 8
<p>I_ds (<b>a</b>, V_ds = 1 V), I_sensing (<b>b</b>) and (<b>c</b>) R-V_g curves of CN-PPV–G transistors to 50 ppm NO₂ in dry air; R-V_g curves of CN-PPV–G transistors to 25 ppm (<b>d</b>), 1 ppm (<b>e</b>) and 100 ppb (<b>f</b>) NO₂ in dry air. 0 s means before NO₂ exposure. NO₂ was not introduced into the testing chamber until the transfer curves of hybrid films show negligible alterations in dry air.</p> Full article ">Figure 9
<p>R-V_g (V_ds = 1 V) curves of CN-PPV–G transistors in the several sensing-refreshing cycles. Testing conditions, 120 s data of 1 ppm NO₂ in dry air.</p> Full article ">

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Supplementary material:
Supplementary File 1 (ZIP, 220 KiB)

12 pages, 1976 KiB  

Open AccessCommunication

The Formation of a Unique 2D Isonicotinate Polymer Driven by Cu(II) Aerobic Oxidation

by Francisco Sánchez-Férez, Teresa Calvet, Mercè Font-Bardia and Josefina Pons

Materials 2023, 16(10), 3724; https://doi.org/10.3390/ma16103724 - 14 May 2023

Cited by 1 | Viewed by 1061

Abstract

The isolation and structural characterization of a unique Cu(II) isonicotinate (ina) material with 4-acetylpyridine (4-acpy) is provided. The formation of [Cu(ina)₂(4-acpy)]_n (1) is triggered by the Cu(II) aerobic oxidation of 4-acpy using O₂. This gradual formation [...] Read more.

The isolation and structural characterization of a unique Cu(II) isonicotinate (ina) material with 4-acetylpyridine (4-acpy) is provided. The formation of [Cu(ina)₂(4-acpy)]_n (1) is triggered by the Cu(II) aerobic oxidation of 4-acpy using O₂. This gradual formation of ina led to its restrained incorporation and hindered the full displacement of 4-acpy. As a result, 1 is the first example of a 2D layer assembled by an ina ligand capped by a monodentate pyridine ligand. The Cu(II)-mediated aerobic oxidation with O₂ was previously demonstrated for aryl methyl ketones, but we extend the applicability of this methodology to heteroaromatic rings, which has not been tested so far. The formation of ina has been identified by ¹H NMR, thus demonstrating the feasible but strained formation of ina from 4-acpy in the mild conditions from which 1 was obtained. Full article

(This article belongs to the Topic Chemistry of 2D Materials)

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Figure 1

Figure 1
<p>Representation of (<b>a</b>) the molecular structure of complex <b>1</b> with atom labeling, (<b>b</b>) the pairing of 4-acpy within the plane displaying an upwards or downwards disposition, and (<b>c</b>) the sql topology.</p> Full article ">Figure 2
<p>Representation of the intermolecular (<b>a</b>) π···π and C-H···O or (<b>b</b>) C-H···π interactions present in complex <b>1</b>. Dashed blue lines stand for C-H··· O interactions, whereas dashed green lines refer to C-H···π and π···π interactions.</p> Full article ">Figure 3
<p>¹H NMR spectra in ACN-<span class="html-italic">d</span>₃ of the catalytic assays: (<b>a</b>) using Cu(NO₃)₂·3H₂O in ACN without O₂ pressure for 18 h at 120 °C; (<b>b</b>) using Cu(OAc)₂·H₂O in ACN at 2.1 bars of O₂ pressure for 18 h at 120 °C; (<b>c</b>) using Cu(NO₃)₂·3H₂O in ACN at 2.1 bars of O₂ pressure for 18 h at 120 °C. Peaks belonging to 4-fopy are identified with green-filled stars, those belonging to 4-acpy are identified with yellow-filled triangles, and those belonging to ina are identified with light blue asterisks.</p> Full article ">Scheme 1
<p>Ouline of the synthetic conditions to the formation of <b>1</b>.</p> Full article ">Scheme 2
<p>Mechanistic pathway for the conversion of 4-acpy into ina or 4-fopy. The orange square highlights the two products identified: ina and 4-fopy. Adapted from [<a href="#B28-materials-16-03724" class="html-bibr">28</a>].</p> Full article ">

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