Research PaperReduction of Au(III) by a β-cyclodextrin polymer in acid medium. A stated unattainable reaction
Introduction
Due to the unique optical, electronic, and chemical properties, gold nanoparticles (AuNPs) offer great potential applications in biomedicine (Gabas, Stepien, Moros, Mitchell, & Fuente, 2016; Peña-González et al., 2017), catalysis (Penhoat et al., 2016; Su, Li, Wang, Zhong, & Wang, 2016), sensor (Hassanzadeh, Khataee, Bagheri, & Lotfi, 2017; Jiang, Zhang, Jin, Wang, & Zhou, 2015), environmental (Dong et al., 2016; Sierra et al., 2016), electronics (Mthethwa, Tuncel, Durmuş, & Nyokong, 2013), among other fields. The preparation of AuNPs by chemical methods are preferred over the physical or biological ones owing to their versatility to control the shape, size and surface chemistry of the nanoparticles (Daniel & Astruc, 2004). Chemical methods consist on reducing a metal precursor salt, usually HAuCl4, with a reducing agent in the presence of a stabilizer under certain conditions of temperature, pH and concentration of the chemicals. Looking toward a chemically eco-friendly methodology, several occurring natural products, like polysaccharides, have been employed as reducing and stabilizing agents in the preparation of AuNPs (Iravani, 2011, Nazirov et al., 2016; Park, Hong, Weyers, Kim, & Linhardt, 2003).
Cyclodextrins (CD) are natural cyclic oligosaccharides, enzymatically produced mainly from starch, composed of 6, 7 or 8 glucopyranoside units (α, β, γCD, respectively) linked by α-(1 → 4) linkage (Villalonga, Cao, & Fragoso, 2007). The main feature of CDs relies on their unique structure that allows them to form stable inclusion complexes with a wide variety of guests containing hydrophobic moieties (Martin, Sánchez, Cao, & Rieumont, 2006). From the three commercially available CDs, βCD is the cheapest one but the less soluble in water (1.85 g at 25 °C) (Szejtli, 1998). This latter drawback can be overcome by crosslinking the βCD units with epichlorohydrin in basic medium to produce a highly water soluble βCD polymer (βCDP) (Martin et al., 2006; Renard, Deratani, Volet, & Sebille, 1997). Additionally, due to the cooperative effect of the βCD units in the polymer, the inclusion constant of the host-guest complex increases (Martin et al., 2006).
Under acid conditions (1 M HCl), the interaction of βCD with Au(III) has been studied and a formation constant of 2400 M−1 was reported (Koshima & Onishi, 1988). Au(III)-βCD interactions necessarily depend on the speciation of the metal ion. H[AuCl4] is most commonly used as the source of Au(III). Aqueous HAuCl4 solution consists of [AuClx(OH)4-x]− species, where x ≥ 2 at low pH and x < 2 at high pH values (Wang, Qian, Bi, & Huang, 2009). The authors observed that the higher the pH, the larger the size and higher the polydispersity of the obtained AuNPs. According to cyclic voltammometric determinations, the reduction potential of [AuClx(OH)4-x]− decreases with a decrease in the pH of the solution.
While some reports state that unmodified cyclodextrins do not suffer any reaction during the reduction of Au(III) (Liu, Male, Bouvrette, & Luong, 2003), more recent works indicate their capacity to reduce Au(III) and Ag(I) by the oxidation of the primary hydroxyl groups of glucopyranose (Devi & Mandal, 2013; Huang, Meng, & Qi, 2009; Pande et al., 2007). These reports clearly state that a high pH (9–12) is a mandatory condition to achieve the reduction of the metal ions. This reduction process should involve the interaction of Au(III) with βCD.
Recently, we reported the formation of gold nanoparticles (AuNPs), capped with a highly water-soluble β-cyclodextrin-epichlorohydrin polymer (βCDP), with citrate acting as reducing agent (Martin-Trasanco, Cao, Esparza-Ponce, García-Pupo, & Montero-Cabrera, 2015). We observed that even in the absence of citrate AuNPs were formed, a result that could be only attributed to an unexpected reducing activity of βCD over Au(III). The mentioned reduction occurred under a stated non-favourable condition since the addition of HAuCl4 decreases the pH value (∼3). This result motivated the study now presented on the capability of βCDP to reduce Au(III) in acid medium.
Section snippets
Experimental part
Tetrachloroauric acid in solution (wt 30%), HAuCl4, β-cyclodextrin hydrated, βCD (97%), and epichlorohydrin, epi, (98%) were purchased from Sigma-Aldrich and were used without further purification. D(+)-glucose anhydrous (>99%) was obtained from Merck. The β-cyclodextrin-epichlorohydrin polymer (βCDP, Mw ≈ 12 kDa, determined by size exclusion chromatography and 3.5 nm of hydrodynamic diameter) was prepared as previously reported (Martin et al., 2006). Freshly purified MilliQ water (18 mΩ/cm) was
Reductive capability of βCDP over Au(III)
In a recent work we encountered evidences of the formation of gold nanoparticles by refluxing HAuCl4 in a solution of a cross-linked β-cyclodextrin-epichlorohydrin polymer (βCDP) in the absence of trisodium citrate as reducing agent (Martin-Trasanco et al., 2015). The appearance of a bluish color solution, the presence of a broad band at 572 nm in the UV–vis spectrum as well as a population with a hydrodynamic diameter of 44 nm in the DLS profile, were some of the evidences that lead us to
Conclusions
For the first time, we have demonstrated the capability of a β-cyclodextrin-epichlorohydrin crosslinked polymer to reduce Au(III) to Au0 in acid medium (pH ̴3). A βCD:[AuCl4]− ratio of 4:1 is necessary to reduce the 50% of the total Au(III) within the first 24 h, at 60 °C. Under these conditions the reaction occurs at a low rate. From these results we suggest a concentration-dependent step mechanism, during the first 24 h, and a diffusion-dependent one for longer time. The primary hydroxyl groups
Acknowledgements
This work was partially supported by the Fondo Nacional de Desarrollo Científico y Tecnológico [Grant FONDECYT-3150205] and by Millennium NucleusRC120001. The authors thanks the support of Dr. Carlos Ornélas, from the NANOTECH at Advanced Materials Research Center (CIMAV), in Chihuahua, Mexico and to the Dr. Cesar Zúñiga and Diego Oyarzún for their fruitful discussion during the work at the laboratory.
References (38)
- et al.
Spontaneous hydrolysis of borohydride required before its catalytic activation by metal nanoparticles
Catalysis Communications
(2016) Spectroscopic studies on β-cyclodextrin
Vibrational Spectroscopy
(1990)- et al.
Synthesis of gold nanoparticles with glycosides: Synthetic trends based on the structures of glycones and aglycones
Carbohydrate Research
(2014) - et al.
One-pot green synthesis of luminescent gold nanoparticles using imidazole derivative of chitosan
Carbohydrate Polymers
(2016) - et al.
Aspects of determining the molecular weight of cyclodextrin polymers and oligomers by static light scattering
Carbohydrate Polymers
(2013) - et al.
Preparation and characterization of water soluble high molecular weight β-cyclodextrin-epichlorohydrin polymers
European Polymer Journal
(1997) Gold nanoparticle synthesis, morphology control, and stabilization facilitated by functional polymers
Chemical Engineering & Technology
(2011)- et al.
Gold nanoparticles: Assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology
Chemical Reviews
(2004) - et al.
Self-assembly of Ag nanoparticles using hydroxypropyl cyclodextrin: Synthesis, characterisation and application for the catalytic reduction of p-nitrophenol
RSC Advances
(2013) - et al.
Selective colorimetric detection of Cr(iii) and Cr(vi) using gallic acid capped gold nanoparticles
Dalton Transactions
(2016)
Colorimetric method for determination of sugars and related substances
Analytical Chemistry
In vitro cell cytotoxicity profile and morphological response to polyoxometalate-stabilised gold nanoparticles
New Journal of Chemistry
Charge transfer spectra of some gold(III) complexes
The Journal of Chemical Physics
Sensitive chemiluminescence determination method for 2,4,6-trinitrotoluene based on the catalytic activity of amine-capped gold nanoparticles
New Journal of Chemistry
Facile synthesis and one-dimensional assembly of cyclodextrin-capped gold nanoparticles and their applications in catalysis and surface-enhanced Raman scattering
The Journal of Physical Chemistry C
Green synthesis of metal nanoparticles using plants
Green Chemistry
In situ controlled sputtering deposition of gold nanoparticles on MnO2 nanorods as surface-enhanced Raman scattering substrates for molecular detection
Dalton Transactions
The missing piece of the mechanism of the Turkevich method: The critical role of citrate protonation
Chemistry of Materials
Adsorption of gold(III) and thallium(III) on β-cyclodextrin polymer from hydrochloric acid solution
Analytical Sciences
Cited by (17)
Light-triggered unconventional therapies with engineered inorganic nanoparticles
2022, Advances in Inorganic ChemistryCitation Excerpt :These intriguing nanostructures can be obtained in a single-step at room temperature and in few minutes by visible light irradiation of an NO photoreleasing tailored β-CD branched polymer, without the need of preformed seeds, external reducing and sacrificial agents, conventional surfactants and stabilizing ligands (Fig. 16). The redox process between NO and Au(III) is favored by the well-known complexation capability of the β-CD branched polymer towards Au metal ions ensuring that the bimolecular reaction between the redox partners occurs mainly within the polymeric network and thus more effectively due to the proximity effect.97 The resulting Au nanostructures are excellent photothermal agents as demonstrated by the fast increase of the temperature to a plateau value above 40 °C after few minutes of irradiation with an 808 nm laser.
Alkoxide structure effect on size and size distribution of Ag, Au and Ag@Au nanoparticles, prepared via alkoxide mild reduction in water
2020, Materials Science and Engineering: BOne-step green synthesis of antibacterial silver nanoparticles embedded in electrospun cyclodextrin nanofibers
2019, Carbohydrate PolymersCitation Excerpt :Under alkaline conditions, CD can catalyze the reduction of Ag(II) to metallic Ag(0) without the requirement of any reducing agent and lead to the formation of Ag-NPs. In this regard, the use of CD molecules as the reducing agent for the synthesis of noble metal nanoparticles in either acidic or alkaline media was reported (Celebioglu & Uyar, 2013; Devi & Mandal, 2013; Huang, Meng, & Qi, 2009; Martin-Trasanco, Cao, Esparza-Ponce, Montero-Cabrera, & Arratia-Pérez, 2017; Pande et al., 2007). According to Pande et al., the basic mechanism was explained by the deprotonation of hydroxy groups of CD at alkaline solutions, which promoted the synthesis of nanoparticles.
Biogenic palladium nanoclusters supported on hybrid nanocomposite 2-hydroxypropyl-β-cyclodextrin/alginate as a recyclable catalyst in aqueous medium
2019, Journal of Molecular LiquidsCitation Excerpt :However, environmental effects, production cost and reused issues still are major barriers for their widespread application in the industry. The recent researches showed that MNPs capped on the biodegradable polysaccharides including starch [9–11], cellulose [12,13], cyclodextrins (CDs) [14–16] and alginate (Alg) [17–20] have displayed high catalytic activities and possess many advantages. Among of them, the cyclodextrins (CDs) and alginate (Alg) are specifically interested due to their capping and stabilization.
Biosynthesized AgNP capped on novel nanocomposite 2-hydroxypropyl-β-cyclodextrin/alginate as a catalyst for degradation of pollutants
2018, Carbohydrate PolymersCitation Excerpt :It is evident that the stable Ag+/HPCD/Alg nanocomposite is obtained after purification by washing with water using centrifugation technique. Many previous reports showed that alginate and CDs might be used efficiently as a reducing and stabilizing agent for in situ synthesis of metallic nanoparticles (Fayaz, Balaji, Girilal, Kalaichelvan, & Venkatesan, 2009; Martin-Trasanco, Cao, Esparza-Ponce, Montero-Cabrera, & Arratia-Perez, 2017; Mastromatteo et al., 2015; Senra et al., 2009; Sharma, Sanpui, Chattopadhyay, & Ghosh, 2012; Zhao, Zhu, Zhu, Huang, & Xia, 2016). However, the attempts on reduction of Ag+/HPCD/Alg gel solution without any reductant at 90 °C for 6 h were failed.
Nanosponge-C<inf>3</inf>N<inf>4</inf> composites as photocatalysts for selective partial alcohol oxidation in aqueous suspension
2023, Photochemical and Photobiological Sciences