Current Status of Platinum Based Nanoparticles: Physicochemical Properties and Selected Applications – A Review
Current Status of Platinum Based Nanoparticles: Physicochemical Properties and Selected Applications – A Review
Platinum-based nanoparticles in electrochemistry, photochemistry and sensors
The present article reviews the synthesis routes and applications of platinum-based nanoparticles in emerging fields such as energy harvesting, health care applications and sensors. Increasingly, more useful, novel and multifunctional materials are needed with fewer side effects. This article provides an overview of Pt-based nanoparticles along with recent applications in electrochemistry, photochemistry, biosensors and gas sensors. In particular, platinum dioxide (Adams’ catalyst) has been used in many chemical reactions including hydrogenation, oxidation and reduction.
An enormous number of metal oxide nanoparticles are utilised and appreciated for their unique properties and applications in the disciplines of nanoscience. Due to their distinct behaviour PtO2 nanoparticles have significant catalytic activity. They were first prepared by Adams and are labelled Adams’ catalyst (1). Adams’ catalyst, or PtO2, has been prepared mostly by colloidal techniques. The metal precursor produces an enhanced form of Pt catalyst after reduction with hydrogen. Finally there is the formation of stable Pt(0) in the form of nanoparticles. This catalyst is used for further applications in chemical reactions.
PtO2 has two different stable states: α-PtO2 and β-PtO2; α-PtO2 has a hexagonal system at ambient pressure and β-PtO2 has an orthorhombic system at high pressure (2). The β-PtO2 displays more than one structure due to the presence of a larger amount of Pt3+ ions leading to the higher volume of β-PtO2 and a smaller amount of oxygen. Pt4+ ions exhibit a tetragonal rutile structure in β-PtO2 due to the maximum number of coulombic communications. Additionally, Pt3+ ions display an orthorhombic structure in β-PtO2 due to the occurrence of high cationic interactions (3). Nanosized PtO2 particles have revealed identical physical and chemical properties. Nano platina has been used to prepare novel materials for magnetic, high conductance, optical and thermal requirements for various specifications (4). Obviously, nanomaterials are currently of great interest, due to their potential physicochemical properties such as optoelectronic, electrical conductivity, mechanical strength, excellent magnetic and thermal properties. Materials having such properties might be introduced for various applications such as photocatalytic degradation, electrochemistry and biosensor applications and these factors are briefly described in this review.
1.1 Platinum Nanoparticles in Nanomaterials
Pt nanoparticles incorporated with tin(IV) oxide nanomaterials were investigated for their electrocatalytic properties through the electrochemical oxygen reduction reaction (ORR) (Pt/SnO2 vs. glassy carbon electrode). Electrochemical assessment showed that the Pt loaded electrode exhibited good activity for the ORR due to its high surface area (5). Pt supported on carbon having a large surface area is used as the cathode in polymer electrolyte fuel cells (PEFCs). However, Pt/SnO2 nanowires have produced higher ORR activity than Pt/C, due to the low surface area of Pt/C as a reference catalyst in the ORR (6). Recently, galvanic exchange reactions have been used to synthesise different types of nanomaterials such as alloys, bimetallic nanoparticles and noble metals like Pt, gold and palladium with heterostructural morphology (7). Cobalt nanoparticles have acted as structure-inducing agents to achieve various kinds of morphology in metals and metal oxide nanomaterials including nanotubes, nanorods, nanowires and nanospheres (8).
Novel Pt-based nanoparticles having excellent physicochemical properties have been prepared with metals such as Pd, lead and iron. Pt nanoparticles were combined with Pd to form a ‘dandelion like’ surface morphology of core-shell nanoparticles. These Pt@Pd core-shell nanoparticles have been used as a highly active catalyst for olefin reduction reactions (9). The Pt@Pd core-shell nanoparticles have also been encapsulated with reduced graphene oxide (rGO) by microwave techniques. The resulting catalyst (Pt@Pd/rGO) had good physicochemical properties and has been used as a catalyst for dehalogenation in aromatic reactions through reduction of olefins with 98% improvement in yield and selectivity. The catalyst was further reusable more than five times in dehalogenation and reduction reactions of olefins. Noble metal-based nanoparticles such as Au@Cu, Au@Pd and Pd@Cu have comparatively good catalytic activity due to their size, surface area and morphology (10) and have been used as catalysts in organic reactions (11, 12). Pt nanoparticles incorporated into other materials have exhibited potential catalytic improvements (13) and can be easily synthesised through physical methods. There has been much focus on graphene oxide (GO) and rGO based core-shell nanomaterials including metal/GO and metal/rGO catalysts for methanol oxidation, metal salt reduction and electrocatalysis, due to their high activity, large surface area, superior electrical conductivity, high stability and recyclability (14). The modification of graphene into GO and rGO through oxidative exfoliation can lead to inadequate surface functionality due to its hydrophobic nature. Because GO and rGO are hydrophilic in nature, the stability of core-shell nanomaterials is maintained. In Pt@Pd/rGO core-shell nanoparticles, a tendency for dehalogenation reactions has been observed with dehalogenation reaction following the order F << Cl < Br < I (15).
1.2 Structural Properties
PtO2 structures were established as tetragonal PtO, Pt3O4, Pt5O6, Pt3O8 and PtO2 as determined by X-ray diffraction (XRD) spectroscopy (16). The structural elucidation of PtO2 as β-PtO2 (cadmium iodide type, space group Pnmm) (17) and α-PtO2 was confirmed to be a hexagonal close packed structure (CdI2 type, space group P-3m1) (18). XRD was used to determine the lattice parameter of α-PtO2 film: a = 3.113 ångström (Å), c = 4.342 Å and lattice parameter of α-PtO2 powder: a = 3.10 Å and c = 4.29–4.41 Å (19). β’-PtO2 has a rutile type structure (space group P42/mnm) (3). PtO2 has an octahedral structure, formed from amalgamation of Pt in six-fold axis and oxygen in three-fold axis. The oxidation state of PtO2 has been found to be +4 and PtO is considered to be +2 which implies a GeS-type structure, even though the Pt atom was six-fold. The Pt-Pt bond length in Pt2 was found to be 2.33 Å (20). Vacancy produces magnetism from oxide combined materials such as calcium oxide (21), zinc oxide (22), magnesium oxide (23), titanium dioxide (24), tin(IV) oxide (25) and hafnium(IV) oxide (26) to group III-nitrides (for example, gallium nitride and boron nitride) (27) and magnetic behaviour has also been established in diamond, graphite and graphene (28). Generally, oxides and nitrides of Pt occupy 2p orbitals or an open d shell with cation/anion vacancies, therefore PtO2 (β-PtO2) has vacancies which stimulate intrinsic magnetism due to the occurrence of the β phase.
The β-PtO2 structure was found to be similar to the calcium chloride type crystal structure and to the TiO2 type crystal structure with distortion (29). The Vienna Ab initio Simulation Package (VASP) was used to calculate the vacancy sites in the crystal system through plane wave and projector augmented wave method (PAW) potential. The plane wave energy was more than 600 electron volts (eV) (30). Coulomb repulsion (Ueff ) plays an important role in band gap energy and β-PtO2 has higher resistivity compared to α-PtO2 with resistivity values of 106 Ω cm and 104 Ω cm respectively (31), however two different oxygen vacancies corresponding to PtO1.958 and PtO1.986 were δ = 0.042 and δ = 0.014 respectively. The energy value between Fermi levels is an unoccupied state at approximately 31 megaelectron volts (meV) and clearly depicts the transformation of electrons from one system into another vacancy state of a and b crystal system (32). There are numbers of planes of α-PtO2 with area identified using the Joint Committee on Powder Diffraction Standards (JCPDS) card, with the planes (0001) and (1010) found to be more stable (33). When excited, the oxygen vacancy in α-PtO2 (0001) and changes in surface area lead to distortion structure as shown in Figure 1(a), Figure 1(b) and Figure 1(c).
1.3 Chemical Reactivity
Heterogeneous catalysts have higher catalytic activity than homogeneous catalysts due to the presence of a large surface area. Additionally, sintered particles of PtO2 possess different activation energies of 3.77 eV to Pt (bulk material) and –2.05 eV to Pt (gas), which depend upon the size of the nanoparticles. High sintering temperatures greater than 427°C provide more entropic driving force for vaporisation due to the low pressure of unstable particles (34). In recent research, the reaction of oxygen on metals such as cobalt, nickel, zinc, copper, Pt and Pd has been used to reduce atmospheric pollution. PtO2 increases the chemical reactivity of CoO/CoAl2O4. The percentage of three capping materials has shown good reactivity in CoO/CoAl2O4, (CoO + 1.0% PtO2)/CoAl2O4 and (CoO + 1.0% Rh2O3)/CoAl2O4, whereas time of reduction reaction was reduced by the addition of PtO2 (35). PtO2 has been applied to a wide range of chemical reactions such as hydrosilylation of olefins (alkenes) (36), defined as the addition of silicon and hydrogen on an unsaturated double bond (C=C) or triple bond (C≡C) (37). PtO2 as a heterogeneous catalyst for the hydrosilylation reaction can be easily removed compared to homogeneous catalysts. Homogeneous catalytic reactivity was first carried out by Karstedt using H2PtCl6 and Pt (PPh3)4 after which it was labelled as Karstedt's catalyst (38). The hydrosilylation reaction was studied using proton nuclear magnetic resonance (1H-NMR) spectroscopy with the ratio of the Si-H singlet of silane at 4.7 ppm and the Si-CH3 singlet of the product at 0.5 ppm (39).
1.4 Effects of Temperature and Air
There are many factors affecting the chemical reaction of metal oxides, such as atmospheric oxygen, the presence of impurities and time. Temperature is one of the most important factors and PtO2 dissociates at a temperature of around 427°C (3). At 400°C, PtO2 decomposes to Pt and O2. A mixture of PtO2 and carbon in helium decomposed at 550°C, as determined by differential thermal analysis (DTA), the same as PtO2/He. When heated to 750°C Pt oxide lost weight as determined by thermogravimetric analysis (TGA), whereas Pt/C produced an exothermic reaction in the presence of He and air at high temperature enhanced by oxygen (40). Normally, transition metals easily corrode during oxidation reactions due to the presence of atmospheric oxygen in air. In a similar way Pt undergoes structural changes at the surface in the presence of air at pressure 0.025 bar to 1000 bar (41, 42). Hence, Pt metal can be treated in air or oxygen at high temperature of 400°C to 500°C to convert directly metal into gas using critical temperature which leaves the vicinity of the metal (43). In the presence of air with Na2O-PtO2 composition a monoclinic cell, space group C’2/c, with a = 5.411 Å, b = 9.386 Å and β = 99°39’ and orthorhombic and monoclinic cell structure with general formula A2BO3 were determined by XRD spectroscopy (44).
2.1 Effective Catalyst in Organic Reactions
Pt is a transition metal with heterogeneous catalytic activity for specific chemical reactions such as removal of hydrogen, transfer of hydrogen and addition of oxygen, as shown in Equations (i)–(iii). In addition, Pt nanoparticles have high surface area and well defined catalytic performance (39). The transition metals Ni and Pd have similar characteristics to Pt nanoparticles. 0.05–2 wt% Pt nanoparticles were mixed with mesoporous silicas (SBA-15 and KIT-6) and aqueous ammonium tetrachloroplatinate(II) and calcined at 500°C to achieve Pt nanoparticles (45, 46). The same size nanoparticles were produced with different crystal systems due to the presence of catalyst to modify their structure (46). The catalytic activities of reaction sites for nanoparticles are dependent on both shape and crystalline facets in different orientations. Some facets exhibit higher catalytic activity than others, due to the involvement of oxygen on the Pt(100) plane and reduction on the Pt(111) plane (47, 48). Pt nanoparticles have been used as a catalyst in reaction with γ-Al2O3 to form nanoparticles of diameter around 0.2–0.8 nm before the elimination of polymer in O2 at 375°C following the deposition and annealing process, as determined by scanning transmission electron microscopy (STEM) and extended X-ray absorption fine structure (EXAFS) (46). Supported Pt nanoparticles exhibit enhanced catalytic properties in the electro-oxidation of methanol due to increase in surface area of the Pt catalyst, which undergoes annealing to form smaller nanoparticles (49–51).
Supported Pt nanomaterials have been used in heterogeneous catalysts, with increased catalytic activity in the oxide phase (18). γ-Alumina doped with 1.5 wt% Pt is susceptible to poisoning by reactants such as nitric oxide, sulfur dioxide and hydrocarbons that could be eliminated at high temperature. The Pt nanoparticles were used as material dopant with Al2O3 for preparation of 2-propanol by an oxidation route, while the same kind of doped substance has produced conversion of more than 80% for the formation of acetone, carbon dioxide and water (46, 52, 53).
Generally, photocatalyst materials are considered to retain their own lifetime efficiently. Photocatalytic degradation of alcohols was studied using a PtO2/TiO2 nanocomposite (54–56). Transition metals ensure high electron capture between the conduction and valence band gap for photocatalytic performance (57). PtO2 has been used to improve the photocatalytic activity of Ti-based materials. With increased Pt content of 1 wt% to 2 wt% the degradation was 61% and 51%, respectively. PtO2 nanoparticles instead of Pt improved the degradation of phenol using sunlight efficiently (58). XRD study confirmed the percentage of phenol degradation for the given samples and the results showed that PtO and PtO2 nanoparticles produced 67.5% and 32.5% of photodegradation respectively. The oxidation states of the metal play a vital role in photocatalytic degradation due to the presence of oxidation states such as Pt0, Pt2+, and Pt4+ (57) and the stability of the metal oxide depended on the number of oxygens present (18, 59). The order of photocatalytic activity and stability of PtO2 are given below in (a) and (b) respectively.
(a) Photocatalytic reactivity order Pt0/PtO2/TiO2 > TiO2 > PtO2/TiO2
(b) Stability of PtO2 order Pt3O4 > Pt2O3 > PtO2 > PtO
The photocatalytic performance of PtO2 has been investigated with Pt0 formed during the CO oxidation reaction and positive potential of α-PtO2. It has twenty times greater catalytic activity compared to Pt0/TiO2 in the presence of sunlight (60). Two different forms of PtO2, α-PtO2 and β-PtO2, were prepared by various techniques but the physicochemical properties of α-PtO2 are still not well understood (2). α-PtO2 nanoparticles suspended in ethanol have been maintained for 20 days without interruption and the sample was examined by gas chromatography to find the chromatographic peaks. α-PtO2 nanoparticles showed outstanding durability for months at ambient temperature without a stabiliser (61). Pt/PtO2 metal nanoparticles have exhibited activity for catalytic application in several reactions including reduction of organic substrates such as substituted phenol, pyridine derivative, methyl ethyl ketone, vanillin and salicylaldehyde (62). Recent research has presented easy ways to identify the photocatalytic efficiency of PtO2 compared with TiO2 and PtO2/TiO2 based materials (57, 63–65).
2.3 Catalysts in Electrochemistry
Pt/PtO2 catalysts can be applied in the field of electrochemistry. PtO2 has a high electron density compared to Pt metal, which can act as a nucleophile and react with electrophiles. Pt/PtO2 has very strong stability in acidic medium during electrolysis at high potential, as studied by mass spectrometry (66). Pt/PtO2 nanoparticles with particle size of 8 nm showed high catalytic activity compared to bulk Pt/PtO2 due to their high surface area (67) and showed enhanced catalytic activity for the hydrogen evolution reaction (HER) with improved particle size control (66). Pt nanoparticles have been used as electrocatalysts in a wide range of applications such as chemical and petrochemical industries, automobiles and fuel cells (68). Pt nanoparticles were used for the manufacture of supported nanopore materials particularly in bipolar electrochemistry. It can be used for fluorescence in electrochemical microscopy. Bipolar electrochemistry is an important aspect of electrochemistry. A reaction is placed between two electrodes. One electrode works as an anode to oxidise the molecules and the other electrode acts as the cathode responsible for the reduction of molecules (69, 70). There are two types of bipolar cells in electrochemistry, open and closed bipolar cells (71). Such bipolar systems are prepared using nanomaterials such as nanoparticles, nanowires, nanorods and nanofilms (72). Pt nanoparticles were used to construct a nanoporous electrode by a focused ion-beam driven deposition technique and Pt nanoparticles were used in a coupled electrochemical cell prepared by focused ion-beam deposition. The supported Pt nanoparticles acted as the electrodes in electrochemical reaction with the help of a potentiostat which is shown in Figure 2.
Pt nanoparticles and nanoporous materials were reacted with gallium ions to fabricate nanoelectrodes with precise size and shape by a high focused beam technique and milling process. Conducting materials such as carbon, gold and tungsten were used to prepare electrodes for electrochemical reactions in which Pt acted as a highly efficient electrode due to its high stability, surface activity and electrocatalytic activity (73–75). Pt nanoparticles showed enhanced activity in the methanol oxidation reaction and have been used with supporting oxide materials in various fields such as catalytic supports (76), magnetic materials (77), photocatalysts (78, 79) and electronic systems (80).
Fe2O3 nanoparticles were found to perform well as catalysts due to their physicochemical properties. Fe2O3 supported by Pt (Fe2O3/Pt) materials have been used as an electrocatalyst for ORRs because of their high surface area, as shown in Equations (iv)–(vi) for the methanol electro-oxidation reaction (81, 82). Figure 3 depicts the formation of Fe2O3 nanoparticles with supported Pt core-shell structure.
Pt nanoparticles are extensively used in biosensor applications, due to their wide range of magnetic properties (83, 84). Transition metals like Fe, Co and Ni, having magnetic characters, can be alloyed with Pt to form stable metal alloys such as Pt-Fe, Pt-Co and Pt-Ni with different physical and chemical properties such as magnetic anisotropy for use in biosensor applications (85). Biosensor materials should maintain a pH range of 5.0–9.0 in dispersed solution and simultaneously the temperature should be kept at 95°C (86). Sensors can be used for applications such as measurement of blood sugar levels for diabetic patients, removal of pollutants in water, food production and biotechnology (87, 88). Immobilised glucose oxidase has been used to predict the concentration of glucose with the help of electrochemical biosensors due to its superior suitability and excellent sensitivity (89). In recent years fibre optic sensors have been fabricated with the help of Pt nanoparticles using localised surface plasmon resonance (LSPR). This principle has mainly focused on chemical sensors and biosensors and is shown in Figure 4. LSPR sensing properties are based on size and shape. Therefore, sensitivity was increased with decreasing particle size and sensitivity was decreased with increasing particle size (for example 10 nm to 50 nm). Surface plasmon resonance (SPR) techniques have been used to investigate surface contact and sensing of liquids as well as other materials (90). Optical fibre was used for various purposes such as simplified and flexible optical design, remote sensing, continuous analysis or monitoring all based on SPR (91). Smaller size metal particles have comparatively high sensing and optical properties (92). Hence Pt metal is not only used in sensor applications but is also applicable in diverse fields such as optoelectronic devices, solar energy, jewellery (93), sensor materials, fuel cells, automotive applications, petroleum refining processes, hydrogen production and biomedical applications (94, 95).
Bisphenol A (BPA, 2,2-bis(4-hydroxyphenyl)propane), is used to manufacture polycarbonate and epoxy resin based plastics for food containers, water packets and plastic based medical containers. The nil effect concentration of BPA presented in drinking water and sea water values has been reported as 1.5 μg l−1 and 0.15 μg l−1 respectively (96, 97). BPA has been implicated in human health problems such as breast cancer, birth defects, infertility, diabetes and obesity (98, 99). Electrochemical sensors have been used to detect BPA through the oxidation reaction (100), by the presence of certain materials such as carbon (101), metal oxides and metals to activate electrodes (102–104). There is a need to find catalytic materials to increase the sensor activity by direct oxidation with no electrode side effects using materials such as carbon and metals such as Pt (105–107).
A new electrode system has been prepared with a porous dual-Pt leaf inside the outward top scanning electrode and inward bottom scanning electrode. A simple arrow indicates the dissemination transportation in the direction of the actively scanning electrode in Figure 5. A membrane between the Pt leaves is used to prevent short circuits during the redox process, as shown in Figure 6 (108). Various factors play an important role for the enhancement of sensing capability, although surface area was found to be the main feature to increase sensor activity. For example, soft Pt provides low sensitivity and reduced selectivity for an enzymatic glucose sensor (109).
2.5 Functionalised Materials in Gas Sensor
Generally, sensors can detect nearby objects. Sensors are classified based on the nature of materials. The first type are physical sensors based on energy sources such as thermal, magnetic and mechanical energy. The second type are chemical sensors which can detect chemicals present in the body, atmosphere or environment. Gas sensors are an essential part of present day life due to the presence of various harmful or easily explosive gases such as isopropanol (IPA), methane, ethanol, methanol, formaldehyde, hydrogen, ammonia, hydrogen sulfide, nitrogen dioxide, sulfur dioxide and carbon monoxide, which cause health issues to human beings such as chronic bronchitis, emphysema and irritation, while high level concentrations can produce effects on the central nervous system, nausea and interior haemorrhage. Pt functionalised SnO2 sheets have been used to detect IPA with a range of response values of 190.50 for 100 ppm of IPA at a controlled temperature of 220°C. It has excellent physicochemical properties and low cost, easy fabrication, high sensitivity and environmental safety (110).
In 2010 almost 665 gas leakages were recorded in Japan, including over 50 explosions. 60% of gas leakages were in residential areas. Therefore, gas sensors are essential to measure the gas and there are several materials already in use. These include platinum oxide (PtOx) on graphene quantum dots on titania (GQDs/TiO2) nanocomposite which behaves as a gas sensor to detect the highly aromatic volatile organic compound IPA with a sensor response range of more than 4.4 for a minimum concentration of 1 ppm and response within 9 seconds at room temperature. In addition, TiO2 nanoparticles exhibit good surface area, unique optoelectronic properties, are easy to synthesise and have a narrow band gap. It can be coupled with graphene quantum dots as the composite materials acting as the gas sensors. Pt modified GQDs/SnO2 thin film shows a transition from P-type to n-type sensing behaviour to sense acetone gas at room temperature with excellent results (111). Therefore, conjugated materials with the addition of metals and metal oxides such as Pt, Pd, Ni, PtO2 and SnO2 respectively can be used to enhance the gas sensing ability. A simple schematic diagram for a gas sensor which contains an alumina tube, sensor and test circuit are shown in Figure 7 (112, 113).
3. Conclusions and Future Work
Nanomaterials play an important role in the fields of materials science, the medical industry, engineering and the polymer industry. This review article has covered selected applications of photocatalysts, electrochemical catalysts, biosensors and gas sensors. Further research work on nanosized Pt/PtO2 will study areas like the stability of Pt materials, environmental aspects, biocompatibility, non-toxicity, suitability for various applications, electrochemical activity and chemical reactivity. There is currently interest in Pt/PtO2 materials for emerging energy applications as it can produce excellent power conversion in various electrochemical applications such as fuel cells, batteries, capacitors, supercapacitors and solar materials, which were not covered in detail here. In fuel cells Pt plays a crucial role in electrochemistry as a counter electrode, due to no or minimum loss of energy conversion. Nanoscale Pt/PtO2 is being used for removal of pollutants like sulfur and methane from industry and residential areas and of CO2 from the polymer industry and heavy-duty vehicles. In addition, it is used for the elimination of toxic and heavy metals such as lead, chromium and arsenic from the environment and from sewage or other waste waters, which can be purified by bio-sensing and electrochemical purification techniques for further usage including drinking if it meets water level recommendations and for agrochemical processes. Pt and PtO2 based nanomaterials are also of great interest for future applications in spacecraft engines and low weight material applications due to their high ductility and thermal resistance properties. Pt and PtO2 nanomaterials also behave as active catalysts in various chemical reactions, due to large surface area and porosity, particularly in the oxide form PtO2 which is also under investigation for doping with other metals and alloys such as PtO2-Pt, PtO2-Fe and PtO2-Co.
F. Bernardi, M. C. M. Alves and J. Morais, J. Phys. Chem. C, 2010, 114, (49), 21434 LINK https://doi.org/10.1021/jp106134r
O. Muller and R. Roy, J. Less Common Metals, 1968, 16, (2), 129 LINK https://doi.org/10.1016/0022-5088(68)90070-2
L. K. Ono, B. Yuan, H. Heinrich and B. R. Cuenya, J. Phys. Chem. C, 2010, 114, (50), 22119 LINK https://doi.org/10.1021/jp1086703
B. He, Y. Ha, H. Liu, K. Wang and K. Y. Liew, J. Colloid Interface Sci., 2007, 308, (1), 105 LINK https://doi.org/10.1016/j.jcis.2006.12.031
A. Rabis, D. Kramer, E. Fabbri, M. Worsdale, R. Kötz and T. J. Schmidt, J. Phys. Chem. C, 2014, 118, (21), 11292 LINK https://doi.org/10.1021/jp4120139
A. Rabis, P. Rodriguez and T. J. Schmidt, ACS Catal., 2012, 2, (5), 864 LINK https://doi.org/10.1021/cs3000864
G. Hu, N. Yang, G. Xu and J. Xu, J. Appl. Geophys., 2018, 150, 118 LINK https://doi.org/10.1016/j.jappgeo.2017.12.011
H. Li, B. Lin, W. Yang, C. Zheng, Y. Hong, Y. Gao, T. Liu and S. Wu, Int. J. Coal Geol., 2016, 154–155, 82 LINK https://doi.org/10.1016/j.coal.2015.12.010
K. J. Datta, K. K. R. Datta, M. B. Gawande, V. Ranc, K. Čépe, V. Malgras, Y. Yamauchi, R. S. Varma and R. Zboril, Chem. Eur. J., 2016, 22, (5), 1577 LINK https://doi.org/10.1002/chem.201503441
A. Goswami, A. K, C. Aparicio, O. Tomanec, M. Petr, R. Pocklanova, M. B. Gawande, R. S. Varma and R. Zboril, ACS Appl. Mater. Interfaces, 2017, 9, (3), 2815 LINK https://doi.org/10.1021/acsami.6b13138
C.-F. Hsia, M. Madasu and M. H. Huang, Chem. Mater., 2016, 28, (9), 3073 LINK https://doi.org/10.1021/acs.chemmater.6b00377
H. M. Song, D. H. Anjum, R. Sougrat, M. N. Hedhili and N. M. Khashab, J. Mater. Chem., 2012, 22, (48), 25003 LINK https://doi.org/10.1039/c2jm35281h
J. W. Hong, S. W. Kang, B.-S. Choi, D. Kim, S. B. Lee and S. W. Han, ACS Nano, 2012, 6, (3), 2410 LINK https://doi.org/10.1021/nn2046828
V. Georgakilas, M. Otyepka, A. B, V. Chandra, N. Kim, K. C. Kemp, P. Hobza, R. Zboril and K. S. Kim, Chem. Rev., 2012, 112, (11), 6156 LINK https://doi.org/10.1021/cr3000412
V. Georgakilas, J. N, K. C, J. A, A. B, K. S. Kim and R. Zboril, Chem. Rev., 2016, 116, (9), 5464 LINK https://doi.org/10.1021/acs.chemrev.5b00620
Y. Abe, M. Kawamura and K. Sasaki, Jpn. J. Appl. Phys., Part 1, 1999, 38, (4A), 2092 LINK https://doi.org/10.1143/jjap.38.2092
Y. Nagano, J. Therm. Anal. Calorim., 2002, 69, (3), 831 LINK https://doi.org/10.1023/a:1020651805170
N. Seriani, W. Pompe and L. C. Ciacchi, J. Phys. Chem. B, 2006, 110, (30), 14860 LINK https://doi.org/10.1021/jp063281r
J. Zhensheng, X. Chanjuan, Z. Qingmei, Y. Feng, Z. Jiazheng and X. Jinzhen, J. Mol. Catal. A: Chem., 2003, 191, (1), 61 LINK https://doi.org/10.1016/s1381-1169(02)00029-8
N. Tian, Z.-Y. Zhou, S.-G. Sun, Y. Ding and Z. L. Wang, Science, 2007, 316, (5825), 732 LINK https://doi.org/10.1126/science.1140484
J. Osorio-Guillén, S. Lany, S. V. Barabash and A. Zunger, Phys. Rev. Lett., 2006, 96, (10), 107203 LINK https://doi.org/10.1103/physrevlett.96.107203
J. A. Chan, S. Lany and A. Zunger, Phys. Rev. Lett., 2009, 103, (1), 016404 LINK https://doi.org/10.1103/physrevlett.103.016404
J. Hu, Z. Zhang, M. Zhao, H. Qin and M. Jiang, Appl. Phys. Lett., 2008, 93, (19), 192503 LINK https://doi.org/10.1063/1.3021085
M. V. Ganduglia-Pirovano, A. Hofmann and J. Sauer, Surf. Sci. Rep., 2007, 62, (6), 219 LINK https://doi.org/10.1016/j.surfrep.2007.03.002
N. H. Hong, N. Poirot and J. Sakai, Phys. Rev. B, 2008, 77, (3), 033205 LINK https://doi.org/10.1103/physrevb.77.033205
C. Das Pemmaraju and S. Sanvito, Phys. Rev. Lett., 2005, 94, (21), 217205 LINK https://doi.org/10.1103/physrevlett.94.217205
P. Dev, Y. Xue and P. Zhang, Phys. Rev. Lett., 2008, 100, (11), 117204 LINK https://doi.org/10.1103/physrevlett.100.117204
J. J. Palacios, J. Fernández-Rossier and L. Brey, Phys. Rev. B, 2008, 77, (19), 195428 LINK https://doi.org/10.1103/physrevb.77.195428
K.-J. Range, F. Rau, U. Klement and A. M. Heyns, Mater. Res. Bull., 1987, 22, (11), 1541 LINK https://doi.org/10.1016/0025-5408(87)90220-0
G. Kresse and J. Furthmüller, Phys. Rev. B, 1996, 54, (16), 11169 LINK https://doi.org/10.1103/physrevb.54.11169
M. C. Jung, H.-D. Kim, M. Han, W. Jo and D. C. Kim, Jpn. J. Appl. Phys., Part 1, 38, (8), 4872 LINK https://doi.org/10.1143/JJAP.38.4872
Y. Yang, O. Sugino and T. Ohno, Phys. Rev. B, 2012, 85, (3), 035204 LINK https://doi.org/10.1103/physrevb.85.035204
T. M. Pedersen, W. X. Li and B. Hammer, Phys. Chem. Chem. Phys., 2006, 8, (13), 1566 LINK https://doi.org/10.1039/b515166j
E. M. Larsson, J. Millet, S. Gustafsson, M. Skoglundh, V. P. Zhdanov and C. Langhammer, ACS Catal., 2012, 2, (2), 238 LINK https://doi.org/10.1021/cs200583u
H. Hong, H. Zhang, T. Han, F. He and H. Jin, Energy Procedia, 2017, 114, 344 LINK https://doi.org/10.1016/j.egypro.2017.03.1175
C. W. Scheeren, J. B. Domingos, G. Machado and J. Dupont, J. Phys. Chem. C, 2008, 112, (42), 16463 LINK https://doi.org/10.1021/jp804870j
‘Hydrosilylation of Alkynes and Their Derivatives – Regio- and Stereoselective Hydrosilylation of Alkynes Catalysed by Late Transition Metal Complexes’, in “Hydrosilylation – A Comprehensive Review on Recent Advances”, Vol. 1, ed. B. Marciniec, Springer Science and Business Media BV, Dordrecht, The Netherlands, 2009, p. 57
N. Sabourault, G. Mignani, A. Wagner and C. Mioskowski, Org. Lett., 2002, 4, (13), 2117 LINK https://doi.org/10.1021/ol025658r
S. Putzien, E. Louis, O. Nuyken and F. E. Kühn, Catal. Sci. Technol., 2012, 2, (4), 725 LINK https://doi.org/10.1039/c2cy00367h
K. Kinoshita, Thermochim. Acta, 1977, 20, (3), 297 LINK https://doi.org/10.1016/0040-6031(77)85084-3
J. Singh, M. Nachtegaal, E. M. C. Alayon, J. Stötzel and J. A. van Bokhoven, ChemCatChem, 2010, 2, (6), 653 LINK https://doi.org/10.1002/cctc.201000061
B. L. M. Hendriksen, S. C. Bobaru and J. W. M. Frenken, Catal. Today, 2005, 105, (2), 234 LINK https://doi.org/10.1016/j.cattod.2005.02.041
Y.-S. Hu, Y.-G. Guo, W. Sigle, S. Hore, P. Balaya and J. Maier, Nature Mater., 2006, 5, (9), 713 LINK https://doi.org/10.1038/nmat1709
C. L. McDaniel, J. Solid State Chem., 1974, 9, (2), 139 LINK https://doi.org/10.1016/0022-4596(74)90065-6
A. F. Lee, J. N. Naughton, Z. Liu and K. Wilson, ACS Catal., 2012, 2, (11), 2235 LINK https://doi.org/10.1021/cs300450y
S. Mostafa, F. Behafarid, J. R, L. K, L. Li, J. C. Yang, A. I. Frenkel and B. R. Cuenya, J. Am. Chem. Soc., 2010, 132, (44), 15714 LINK https://doi.org/10.1021/ja106679z
R. Xu, D. Wang, J. Zhang and Y. Li, Chem. – An Asian J., 2006, 1, (6), 888 LINK https://doi.org/10.1002/asia.200600260
V. Komanicky, H. Iddir, K.-C. Chang, A. Menzel, G. Karapetrov, D. Hennessy, P. Zapol and H. You, J. Am. Chem. Soc., 2009, 131, (16), 5732 LINK https://doi.org/10.1021/ja900459w
G. Gökağaç and B. J. Kennedy, Zeitschrift für Naturforsch. B, 2002, 57, (2), 193 LINK https://doi.org/10.1515/znb-2002-0211
A. S. Aricò, A. K. Shukla, K. M. El-Khatib, P. Cretì and V. Antonucci, J. Appl. Electrochem., 1999, 29, (6), 673 LINK https://doi.org/10.1023/a:1003538230286
D.-J. Guo and H.-L. Li, J. Electroanal. Chem., 2004, 573, (1), 197 LINK https://doi.org/10.1016/s0022-0728(04)00369-9
J. H. Zhang, X. L. Zhou and J. A. Wang, J. Mol. Catal. A: Chem., 2006, 247, (1–2), 222 LINK https://doi.org/10.1016/j.molcata.2005.11.055
N. Burgos, M. Paulis, M. Mirari Antxustegi and M. Montes, Appl. Catal. B: Environ., 2002, 38, (4), 251 LINK https://doi.org/10.1016/s0926-3373(01)00294-6
S. K. Parayil, H. S. Kibombo, C.-M. Wu, R. Peng, T. Kindle, S. Mishra, S. P. Ahrenkiel, J. Baltrusaitis, N. M. Dimitrijevic, T. Rajh and R. T. Koodali, J. Phys. Chem. C, 2013, 117, (33), 16850 LINK https://doi.org/10.1021/jp405727k
W. Y. Teoh, L. Mädler and R. Amal, J. Catal., 2007, 251, (2), 271 LINK https://doi.org/10.1016/j.jcat.2007.08.008
H. Wang, Z. Wu, Y. Liu and Y. Wang, Chemosphere, 2009, 74, (6), 773 LINK https://doi.org/10.1016/j.chemosphere.2008.10.032
H. S. Kibombo, C.-M. Wu, R. Peng, J. Baltrusaitis and R. T. Koodali, Appl. Catal. B: Environ., 2013, 136–137, 248 LINK https://doi.org/10.1016/j.apcatb.2013.01.062
F. B. Li and X. Z. Li, Chemosphere, 2002, 48, (10), 1103 LINK https://doi.org/10.1016/s0045-6535(02)00201-1
N. Seriani, Z. Jin, W. Pompe and L. C. Ciacchi, Phys. Rev. B, 2007, 76, (15), 155421 LINK https://doi.org/10.1103/physrevb.76.155421
A. V. Vorontsov, E. N. Savinov and J. Zhensheng, J. Photochem. Photobiol. A: Chem., 1999, 125, (1–3), 113 LINK https://doi.org/10.1016/s1010-6030(99)00073-8
M.-R. Gao, Z.-Y. Lin, J. Jiang, C.-H. Cui, Y.-R. Zheng and S.-H. Yu, Chem. - A Eur. J., 2012, 18, (27), 8423 LINK https://doi.org/10.1002/chem.201200353
D. A. Svintsitskiy, L. S. Kibis, A. I. Stadnichenko, S. V. Koscheev, V. I. Zaikovskii and A. I. Boronin, ChemPhysChem, 2015, 16, (15), 3318 LINK https://doi.org/10.1002/cphc.201500546
B. Sun, A. V. Vorontsov and P. G. Smirniotis, Langmuir, 2003, 19, (8), 3151 LINK https://doi.org/10.1021/la0264670
C. A. Emilio, M. I. Litter, M. Kunst, M. Bouchard and C. Colbeau-Justin, Langmuir, 2006, 22, (8), 3606 LINK https://doi.org/10.1021/la051962s
B. Sun, P. G. Smirniotis and P. Boolchand, Langmuir, 2005, 21, (24), 11397 LINK https://doi.org/10.1021/la051262n
M. Sarno and E. Ponticorvo, Int. J. Hydrogen Energy, 2017, 42, (37), 23631 LINK https://doi.org/10.1016/j.ijhydene.2017.03.017
D. Miller, H. Sanchez Casalongue, H. Bluhm, H. Ogasawara, A. Nilsson and S. Kaya, J. Am. Chem. Soc., 2014, 136, (17), 6340 LINK https://doi.org/10.1021/ja413125q
G.-Y. Zhao and H.-L. Li, Appl. Surf. Sci., 2008, 254, (10), 3232 LINK https://doi.org/10.1016/j.apsusc.2007.10.086
J. P. Guerrette, S. M. Oja and B. Zhang, Anal. Chem., 2012, 84, (3), 1609 LINK https://doi.org/10.1021/ac2028672
J. T. Cox, J. P. Guerrette and B. Zhang, Anal. Chem., 2012, 84, (20), 8797 LINK https://doi.org/10.1021/ac302219p
S. E. Fosdick, K. N. Knust, K. Scida and R. M. Crooks, Angew. Chem. Int. Ed., 2013, 52, (40), 10438 LINK https://doi.org/10.1002/anie.201300947
A. Lundgren, S. Munktell, M. Lacey, M. Berglin and F. Björefors, ChemElectroChem, 2016, 3, (3), 378 LINK https://doi.org/10.1002/celc.201500413
R. Hao and B. Zhang, Anal. Chem., 2016, 88, (1), 614 LINK https://doi.org/10.1021/acs.analchem.5b03548
J. Clausmeyer and W. Schuhmann, TrAC Trends Anal. Chem., 2016, 79, 46 LINK https://doi.org/10.1016/j.trac.2016.01.018
Y. Li, D. Bergman and B. Zhang, Anal. Chem., 2009, 81, (13), 5496 LINK https://doi.org/10.1021/ac900777n
I. X. Green, W. Tang, M. Neurock and J. T. Yates, Science, 2011, 333, (6043), 736 LINK https://doi.org/10.1126/science.1207272
V. Subramanian, E. E. Wolf and P. V. Kamat, J. Phys. Chem. B, 2003, 107, (30), 7479 LINK https://doi.org/10.1021/jp0275037
S. Sato, R. Asahi, T. Morikawa, T. Ohwaki, K. Aoki and Y. Taga, Science, 2002, 295, (5555), 626 LINK https://doi.org/10.1126/science.295.5555.626
R. K. Nagarale, U. Hoss and A. Heller, J. Am. Chem. Soc., 2012, 134, (51), 20783 LINK https://doi.org/10.1021/ja3103549
J. W. Hennek, Y. Xia, K. Everaerts, M. C, A. Facchetti and T. J. Marks, ACS Appl. Mater. Interfaces, 2012, 4, (3), 1614 LINK https://doi.org/10.1021/am201776p
V. M. Dhavale and S. Kurungot, J. Phys. Chem. C, 2012, 116, (13), 7318 LINK https://doi.org/10.1021/jp300628j
S. M. Devi, A. Nivetha and I. Prabha, J. Supercond. Novel Magn., 2018, Review Paper LINK https://doi.org/10.1007/s10948-018-4929-8
J. B. Tracy, D. N. Weiss, D. P. Dinega and M. G. Bawendi, Phys. Rev. B, 2005, 72, (6), 064404 LINK https://doi.org/10.1103/physrevb.72.064404
S. Behrens, H. Bönnemann, N. Matoussevitch, A. Gorschinski, E. Dinjus, W. Habicht, J. Bolle, S. Zinoveva, N. Palina, J. Hormes, H. Modrow, S. Bahr and V. Kempter, J. Phys.: Condens. Matter, 2006, 18, (38), S2543 LINK https://doi.org/10.1088/0953-8984/18/38/s02
X. Luo, A. Morrin, A. J. Killard and M. R. Smyth, Electroanalysis, 2006, 18, (4), 319 LINK https://doi.org/10.1002/elan.200503415
I. L. Medintz, H. T. Uyeda, E. R. Goldman and H. Mattoussi, Nature Mater., 2005, 4, (6), 435 LINK https://doi.org/10.1038/nmat1390
A. Heller and B. Feldman, Chem. Rev., 2008, 108, (7), 2482 LINK https://doi.org/10.1021/cr068069y
L. Meng, J. Jin, G. Yang, T. Lu, H. Zhang and C. Cai, Anal. Chem., 2009, 81, (17), 7271 LINK https://doi.org/10.1021/ac901005p
W.-Z. Jia, K. Wang, Z.-J. Zhu, H.-T. Song and X.-H. Xia, Langmuir, 2007, 23, (23), 11896 LINK https://doi.org/10.1021/la7020269
J. Homola, Sensors Actuators B: Chem., 1997, 41, (1–3), 207 LINK https://doi.org/10.1016/s0925-4005(97)80297-3
A. K. Sharma and B. D. Gupta, Sensors Actuators B: Chem., 2004, 100, (3), 423 LINK https://doi.org/10.1016/j.snb.2004.02.013
S. Lal, S. Link and N. J. Halas, Nature Photonics, 2007, 1, (11), 641 LINK https://doi.org/10.1038/nphoton.2007.223
J. Hurly and P. T. Wedepohl, J. Mater. Sci., 1993, 28, (20), 5648 LINK https://doi.org/10.1007/bf00367841
L. M. Velichkina, A. N. Pestryakov, A. V. Vosmerikov, I. V. Tuzovskaya, N. E. Bogdanchikova, M. Avalos, M. Farias and H. Tiznado, Pet. Chem., 2008, 48, (3), 201 LINK https://doi.org/10.1134/s0965544108030055
A. Chen and P. Holt-Hindle, Chem. Rev., 2010, 110, (6), 3767 LINK https://doi.org/10.1021/cr9003902
H. Yin, L. Cui, S. Ai, H. Fan and L. Zhu, Electrochim. Acta, 2010, 55, (3), 603 LINK https://doi.org/10.1016/j.electacta.2009.09.020
G. M. Klečka, C. A. Staples, K. E. Clark, N. van der Hoeven, D. E. Thomas and S. G. Hentges, Environ. Sci. Technol., 2009, 43, (16), 6145 LINK https://doi.org/10.1021/es900598e
L. N. Vandenberg, R. Hauser, M. Marcus, N. Olea and W. V. Welshons, Reprod. Toxicol., 2007, 24, (2), 139 LINK https://doi.org/10.1016/j.reprotox.2007.07.010
H. Mielke and U. Gundert-Remy, Toxicol. Lett., 2009, 190, (1), 32 LINK https://doi.org/10.1016/j.toxlet.2009.06.861
K. V. Ragavan, N. K. Rastogi and M. S. Thakur, TrAC Trends Anal. Chem., 2013, 52, 248 LINK https://doi.org/10.1016/j.trac.2013.09.006
J. A. Rather and K. De Wael, Sensors Actuators B: Chem., 2013, 176, 110 LINK https://doi.org/10.1016/j.snb.2012.08.081
L. Hu, C.-C. Fong, X. Zhang, L. L. Chan, P. K. S. Lam, P. K. Chu, K.-Y. Wong and M. Yang, Environ. Sci. Technol., 2016, 50, (8), 4430 LINK https://doi.org/10.1021/acs.est.5b05857
Z. Zheng, Y. Du, Z. Wang, Q. Feng and C. Wang, Analyst, 2013, 138, (2), 693 LINK https://doi.org/10.1039/c2an36569c
R. Wannapob, P. Thavarungkul, S. Dawan, A. Numnuam, W. Limbut and P. Kanatharana, Electroanalysis, 2017, 29, (2), 472 LINK https://doi.org/10.1002/elan.201600371
V. Malgras, H. Ataee-Esfahani, H. Wang, B. Jiang, C. Li, K. C.-W. Wu, J. H. Kim and Y. Yamauchi, Adv. Mater., 2015, 28, (6), 993 LINK https://doi.org/10.1002/adma.201502593
Q. Shen, L. Jiang, H. Zhang, Q. Min, W. Hou and J.-J. Zhu, J. Phys. Chem. C, 2008, 112, (42), 16385 LINK https://doi.org/10.1021/jp8060043
D.-S. Park, M.-S. Won, R. N. Goyal and Y.-B. Shim, Sensors Actuators B: Chem., 2012, 174, 45 LINK https://doi.org/10.1016/j.snb.2012.08.017
H. R. Zafarani, L. Rassaei, E. J. R. Sudhölter, B. D. B. Aaronson and F. Marken, Sensors Actuators B: Chem., 2018, 255, 2904 LINK https://doi.org/10.1016/j.snb.2017.09.110
I. T. Bae, E. Yeager, X. Xing and C. C. Liu, J. Electroanal. Chem. Interfacial Electrochem., 1991, 309, (1–2), 131 LINK https://doi.org/10.1016/0022-0728(91)87009-s
C. Dong, X. Liu, X. Xiao, G. Chen, Y. Wang and I. Djerdj, J. Mater. Chem. A, 2014, 2, (47), 20089 LINK https://doi.org/10.1039/c4ta04251d
S. Shao, Y. Chen, S. Huang, F. Jiang, Y. Wang and R. Koehn, RSC Adv., 2017, 7, (63), 39859 LINK https://doi.org/10.1039/c7ra07478f
B. Yang, J. Liu, H. Qin, Q. Liu, X. Jing, H. Zhang, R. Li, G. Huang and J. Wang, Ceram. Int., 2018, 44, (9), 10426 LINK https://doi.org/10.1016/j.ceramint.2018.03.059
N. Murata, T. Suzuki, M. Kobayashi, F. Togoh and K. Asakura, Phys. Chem. Chem. Phys., 2013, 15, (41), 17938 LINK https://doi.org/10.1039/c3cp52490f
C. Sakthivel is a PhD Research Scholar, under the guidance of I. Prabha at the Department of Chemistry, Bharathiar University, Coimbatore, India. His current laboratory research focuses on novel nanomaterials with catalysis, energy and biological based applications. He has received a BSc in Chemistry from Periyar University, Tamil Nadu, India and an MSc in Chemistry, Bharathidasan University, Tamil Nadu, India. Additionally, he has completed a Bachelors Degree in Education from Tamil Nadu Teacher Education University, Chennai, India. He has published a review paper in Materials Today Sustainability, published by Elsevier. He has presented a full-length paper in international conference proceedings and was awarded best paper presentation. He has work experience and knowledge in paints with applications in the PG project. He has attended various national and international conferences at various institutions.
L. Keerthana is an MPhil Research Scholar under the guidance of I. Prabha at the Department of Chemistry, Bharathiar University, Coimbatore, India. Her current laboratory research focuses on novel nanomaterials with catalysis, energy and biological based applications. She holds both undergraduate and postgraduate degrees in Chemistry. She has published a paper in Materials Today Sustainability. She has presented in national and international conferences. Her research area of interest is materials chemistry.
I. Prabha completed her MSc in Chemistry from Gandhigram Rural Institute, Dindigu, India and MPhil in Chemistry from Madurai Kamaraj University, Madurai, Tamil Nadu, India. She completed her PhD at the Department of Chemistry, Sathyabama University, Chennai, Tamil Nadu, India. She has worked as an Associate Professor at the Department of Chemistry, Bharathiar University, Coimbatore, India since November 2016. Her research focuses on the chemistry of nanomaterials and its recent applications, novel catalysts and advanced photocatalysis, green catalysis and its synthesis for societal benefits, water purification and quality assessment. She has published research articles in various national and international journals. She has presented and attended various international and national conferences, seminars and workshops. Currently she is guiding PhD and MPhil students. She has written book chapters for BE, BTech and MSc (Chemistry) students.