Rapid and sensitive detection of box turtles using an electrochemical DNA biosensor based on a gold/graphene nanocomposite

• Abu Hashem,
• M. A. Motalib Hossain,
• Ab Rahman Marlinda,
• Mohammad Al Mamun,
• Khanom Simarani and
• Mohd Rafie Johan

Beilstein J. Nanotechnol. 2022, 13, 1458–1472, doi:10.3762/bjnano.13.120

• , Benvidi et al. [60] reported 35 °C as the hybridisation temperature, whereas Kusnin et al. [57] and Hartati et al. [61] reported 40 °C and room temperature as the hybridisation temperature, respectively. These results are similar to and corroborate our findings. The pH value is also an important parameter

• for hybridisation efficiency. In the drop-casting method, there is little scope to conduct experiments at variable pH values due to the use of the microlitre scale solution. Usually, DNA hybridisation efficiency peaks between pH 7.5 and 8.5 due to good accessibility and binding affinity [62]. For this

• experiment, pH 7.4 was chosen, which is close to physiological pH, and a similar pH value was reported by Kusnin et al. [57] in hybridisation biosensing experiments. Selectivity of the electrochemical biosensor Electrodes with hybridised DNA were incubated in MB for 30 min, washed with deionised water, and

Coherent amplification of radiation from two phase-locked Josephson junction arrays

• Mikhail A. Galin,
• Vladimir M. Krasnov,
• Ilya A. Shereshevsky,
• Nadezhda K. Vdovicheva and
• Vladislav V. Kurin

Beilstein J. Nanotechnol. 2022, 13, 1445–1457, doi:10.3762/bjnano.13.119

• (Figure 2, Figure 5b,c). The inductances are equal to 100 pH while the internal resistance of the power supplies has the value of 90 Ω. The latter allows for measurements of IVCs close to the regime of constant bias current. However, the electromotive force of the power supply is, in fact, the primary

• containing 100 JJs. The dimensions of the substrate (x × y × z) are 2.0 × 0.6 × 0.3 mm, and its dielectric permittivity is ε = 12. The inductances have the value 100 pH while the internal resistance of the power supplies is 90 Ω. The junctions are described in the RSJ model [20] with parameters Ic = 2.5 mA

Facile preparation of Au- and BODIPY-grafted lipid nanoparticles for synergized photothermal therapy

• Yuran Wang,
• Xudong Li,
• Haijun Chen and
• Yu Gao

Beilstein J. Nanotechnol. 2022, 13, 1432–1444, doi:10.3762/bjnano.13.118

• release properties were evaluated in PBS with different pH values (pH 7.4 and 5.5). AB-LNPs dispersion (2 mL) in a dialysis bag was placed in 20 mL release medium. After 2 h and after 6 h, the sample was irradiated with a 680 nm laser (0.5 W/cm2, 60 s). At predetermined time points, 1 mL of solution was

• AB-LNPs could respond to laser irradiation and release the drug from LNPs, in vitro release studies of AB-LNPs were performed in PBS (pH 7.4 or 5.4) at 37 °C with or without 680 nm laser irradiation (0.5 W/cm2, 1 min). Two laser irradiations were carried out at 2 and 6 h for easier observation of the

• accelerated release. The laser irradiation accelerated the release of BDP from AB-LNPs. The accumulated released amount of AB-LNPs in pH 7.4 with laser irradiation was almost 65.7% at 36 h while the accumulated released amount of AB-LNPs without laser irradiation was only 50% (Figure 3c). The results can be

Orally administered docetaxel-loaded chitosan-decorated cationic PLGA nanoparticles for intestinal tumors: formulation, comprehensive in vitro characterization, and release kinetics

• Sedat Ünal,
• Osman Doğan and
• Yeşim Aktaş

Beilstein J. Nanotechnol. 2022, 13, 1393–1407, doi:10.3762/bjnano.13.115

• . However, the occurrence of colon carcinomas in the most distant region of the gastrointestinal tract makes the development of oral formulations for colon carcinomas more difficult than that of other formulations [10]. Considering multiple factors such as the variable pH of the gastrointestinal tract

• charged mucin, decreased pH value, and increased temperature, may provide design clues for mucoadhesive polymeric nanoparticles that have a potential to exhibit higher drug release or help to alleviate colorectal tumor in colon region [11][19][20]. PLGA is a physiologically biocompatible and biodegradable

• results proved the positive effect of CS on EE and DL by showing consistency with results of previous studies. In vitro release studies of DCX from nanoparticles In order to mimic the GIT with regard to both pH and retention time, in vitro release studies for each formulation were carried out in three

LED-light-activated photocatalytic performance of metal-free carbon-modified hexagonal boron nitride towards degradation of methylene blue and phenol

• Nirmalendu S. Mishra and
• Pichiah Saravanan

Beilstein J. Nanotechnol. 2022, 13, 1380–1392, doi:10.3762/bjnano.13.114

• charge is an important parameter which governs the adsorption of the pollutant moiety over the photocatalyst. Thus, it becomes very important to study the variation of surface charge of the MBN-80. The variation of surface charge over MBN-80 in terms of pH value and isoelectric point of the solution was

• studied through zeta potential analysis (depicted in Figure 4b). It was observed that the surface of MBN-80 is positively charged at lower pH values which gradually increases with the increase in pH range. The isoelectric point was determined to be at pH 5.08. The MBN-80 was found to be negatively charged

• with a zeta potential of −20 mV at a neutral pH. This implies that the surface of MBN-80 is negatively charged above pH 5.08 which results in better adsorptive ability towards positively charged pollutant moieties and vice-versa. Optical studies The UV–vis light harvesting characteristics (absorbance

Supramolecular assembly of pentamidine and polymeric cyclodextrin bimetallic core–shell nanoarchitectures

• Alexandru-Milentie Hada,
• Nina Burduja,
• Marco Abbate,
• Claudio Stagno,
• Guy Caljon,
• Louis Maes,
• Nicola Micale,
• Massimiliano Cordaro,
• Angela Scala,
• Antonino Mazzaglia and
• Anna Piperno

Beilstein J. Nanotechnol. 2022, 13, 1361–1369, doi:10.3762/bjnano.13.112

• the release of Pent within 24 h. This is the time of the in vitro biological test and the activity of Pent included into the CD cavity should be better evaluated in vivo according to the literature [27]. To clarify this point, release experiments of PolyCD@Pent have been carried out in PBS (pH 7.4) at

Recent trends in Bi-based nanomaterials: challenges, fabrication, enhancement techniques, and environmental applications

• Vishal Dutta,
• Ankush Chauhan,
• Ritesh Verma,
• C. Gopalkrishnan and
• Van-Huy Nguyen

Beilstein J. Nanotechnol. 2022, 13, 1316–1336, doi:10.3762/bjnano.13.109

• surfactant-free hydrothermal technique [55]. According to the results, the pH value has a significant impact on shape, surface area, particle size, and V–O bond length. The grain size was reduced when the pH value was raised, and the crystal structure became more closely stacked. Under visible-light

• irradiation, the RhB photodegradation efficiency of the coralloid particles produced at pH 7 was about four times greater than that of the sample synthesized at pH 0.5. The increased photocatalytic activity was caused by several factors, such as a synergistic effect of highly exposed (010) grain facets, an

• simple hydrothermal synthesis for preparing 2D BiOCl nanosheets [83]. This was accomplished by altering the pH value of the precursor solution and using of dulcitol (C6H14O6) as surfactant. The pH value substantially influenced the thickness of the nanosheets and the fraction of exposed (001) facets. The

Studies of probe tip materials by atomic force microscopy: a review

• Ke Xu and
• Yuzhe Liu

Beilstein J. Nanotechnol. 2022, 13, 1256–1267, doi:10.3762/bjnano.13.104

• nanoclusters to establish a rapid detection method for glyphosate, dimethoate, ethion, methylphosphine and carbaryl. A novel fluorescent "on-off-on" probe was constructed to detect the organophosphorus pesticide glyphosate. Under strongly alkaline conditions (pH is approximately 12), the P–S bonds of ethion

• particles were homogeneous; the maximum absorption wavelength was 518 nm with narrow peak width in the UV spectrophotometer 400–700 nm scan; the purified HBsAg Mab concentration was 65 mg/mL; the optimal protein protection amount was 32.5 μg per mL of colloidal gold at pH 8.2; the quality of the probe was

• development of the colloidal gold probe. The preparation of a high-quality colloidal gold probe was a prerequisite for the detection of Lm, in which the pH value and the amount of labeled scFv were two critical influencing factors. Therefore, the study was optimized for both factors. Also, the colloidal gold

Design of surface nanostructures for chirality sensing based on quartz crystal microbalance

• Yinglin Ma,
• Xiangyun Xiao and
• Qingmin Ji

Beilstein J. Nanotechnol. 2022, 13, 1201–1219, doi:10.3762/bjnano.13.100

• enantiomer. As the intermolecular interactions with the analyte also play a role in chiral recognition, the group also studied the influence of pH values. The highest recognition efficiency was shown at pH 10 since basic conditions may promote the formation of stronger hydrogen bonding between the carboxyl

• cavity of native β-CD ranges from 0.60 to 0.65 nm and matches well with biphenyl or naphthalene groups, but not with methyl lactate, ethyl lactate, or 2-octanol. Conversely, β-CD with phenylcarbamate (Ph-β-CD) and 4-methoxyphenylcarbamate groups (MP-β-CD) possess smaller cavities and more rigid

Recent advances in green carbon dots (2015–2022): synthesis, metal ion sensing, and biological applications

• Aisha Kanwal,
• Naheed Bibi,
• Sajjad Hyder,
• Arif Muhammad,
• Hao Ren,
• Jiangtao Liu and
• Zhongli Lei

Beilstein J. Nanotechnol. 2022, 13, 1068–1107, doi:10.3762/bjnano.13.93

• pH stability. Animal extract Dehvari et al. converted seafood waste into valuable materials by using crab shell as a natural precursor to form highly fluorescent N-CDs by a sono-chemical approach. A N-CDs/folic acid nanoprobe was synthesized by conjugating N-CDs with folic acid, which could be used

Biomimetic chitosan with biocomposite nanomaterials for bone tissue repair and regeneration

• Se-Kwon Kim,
• Sesha Subramanian Murugan,
• Pandurang Appana Dalavi,
• Sebanti Gupta,
• Sukumaran Anil,
• Gi Hun Seong and
• Jayachandran Venkatesan

Beilstein J. Nanotechnol. 2022, 13, 1051–1067, doi:10.3762/bjnano.13.92

• . Figure 3 was reproduced from [107], (© 2017 J. C. Forero et al., published by MDPI, distributed under the terms of the Creative Commons Attribution 4.0 International License, https://creativecommons.org/licenses/by/4.0). The ciprofloxacin release rate (%) from several composite films at pH 7.4. Figure 4

Electrocatalytic oxygen reduction activity of AgCoCu oxides on reduced graphene oxide in alkaline media

• Iyyappan Madakannu,
• Indrajit Patil,
• Bhalchandra Kakade and
• Kasibhatta Kumara Ramanatha Datta

Beilstein J. Nanotechnol. 2022, 13, 1020–1029, doi:10.3762/bjnano.13.89

• the overall performance of the reaction [3][4]. There is an increasing use of platinum catalysts with diverse morphologies and the combination with noble and non-noble metal-based alloy/multimetallic nanoparticles (NPs) as potential electrocatalysts under extreme pH values [5][6][7][8][9][10][11][12

Solar-light-driven LaFe_xNi_1−xO₃ perovskite oxides for photocatalytic Fenton-like reaction to degrade organic pollutants

• Chao-Wei Huang,
• Shu-Yu Hsu,
• Jun-Han Lin,
• Yun Jhou,
• Wei-Yu Chen,
• Kun-Yi Andrew Lin,
• Yu-Tang Lin and
• Van-Huy Nguyen

Beilstein J. Nanotechnol. 2022, 13, 882–895, doi:10.3762/bjnano.13.79

• ), Chengalpattu district, Kelambakkam, Tamil Nadu, 603103, India 10.3762/bjnano.13.79 Abstract LaFexNi1−xO3 perovskite oxides were prepared by the sol–gel method under various conditions, including different pH values (pH 0 and pH 7) and different calcination temperatures (500–800 °C) as well as different Fe/Ni

• decompose the methylene blue molecules. Accordingly, the synthesis condition of pH 0, calcination temperature at 700 °C, and Fe/Ni ratio = 7/3 could form LaFe0.7Ni0.3O3 perovskite oxides as highly efficient photocatalysts. Moreover, various conditions during the photocatalytic degradation were verified

• , such as pH value, catalyst dosage, and the additional amount of H2O2. LaFe0.7Ni0.3O3 perovskite oxides could operate efficiently under pH 3.5, catalyst dosage of 50 mg/150 mL, and H2O2 concentration of 133 ppm to decompose the MB dye in the 1st order kinetic rate constant of 0.0506 s−1. Keywords

DNA aptamer selection and construction of an aptasensor based on graphene FETs for Zika virus NS1 protein detection

• Nathalie B. F. Almeida,
• Thiago A. S. L. Sousa,
• Viviane C. F. Santos,
• Camila M. S. Lacerda,
• Thais G. Silva,
• Rafaella F. Q. Grenfell,
• Flavio Plentz and
• Antero S. R. Andrade

Beilstein J. Nanotechnol. 2022, 13, 873–881, doi:10.3762/bjnano.13.78

• solution dispersed in 1 mM PBS (phosphate-buffered saline: 0.0001 M phosphate buffer, 0.000027 M potassium chloride, and 0.00137 M sodium chloride), pH 7.4. After incubation, the graphene devices were rinsed with 1 mM PBS, followed by sequential rinsing with deionized water and drying in a nitrogen flow

Self-assembly of C₆₀ on a ZnTPP/Fe(001)–p(1 × 1)O substrate: observation of a quasi-freestanding C₆₀ monolayer

• Guglielmo Albani,
• Michele Capra,
• Alessandro Lodesani,
• Alberto Calloni,
• Gianlorenzo Bussetti,
• Marco Finazzi,
• Franco Ciccacci,
• Alberto Brambilla,
• Lamberto Duò and
• Andrea Picone

Beilstein J. Nanotechnol. 2022, 13, 857–864, doi:10.3762/bjnano.13.76

• ZnTPP spectrum in Figure 3, the UPS peaks related to the main molecule ring and to the phenyl groups are labeled “R” and “Ph” [52][53], respectively, according to theoretical simulations performed on metal tetraphenyl porphyrins and metal porphyrins [54]. When an additional single layer of C60 is added

Gelatin nanoparticles with tunable mechanical properties: effect of crosslinking time and loading

• Agnes-Valencia Weiss,
• Daniel Schorr,
• Julia K. Metz,
• Metin Yildirim,
• Saeed Ahmad Khan and
• Marc Schneider

Beilstein J. Nanotechnol. 2022, 13, 778–787, doi:10.3762/bjnano.13.68

• macromolecules, such as proteins [12] and peptides [13], or in the field of gene delivery [14]. The surface charge of gelatin nanoparticles at physiological pH can be easily influenced by the choice of gelatin type [15]. Crosslinking of gelatin nanoparticles is still inevitable to obtain particles that are

• polydispersity index (PdI) from 0.075 to 0.115, indicating a narrow size distribution. Crosslinking for 15 min did not result in stable particles with uniform colloidal properties. The surface charge of gelatin nanoparticles is clearly pH-dependent. At a pH value of 7.5 ± 0.1, the zeta potential values ranged

• pH (−36.0 ± 1.18 mV). The achieved entrapment efficiency was comparable to the loading determined in a previous study in our lab [12]. Crosslinking degree and Young’s moduli Regarding the mechanical properties of the gelatin nanoparticles, a clear dependency of Young’s moduli on the crosslinking time

Recent advances in nanoarchitectures of monocrystalline coordination polymers through confined assembly

• Lingling Xia,
• Qinyue Wang and
• Ming Hu

Beilstein J. Nanotechnol. 2022, 13, 763–777, doi:10.3762/bjnano.13.67

• coordination polymers as envelopes for the bio-entities. On the basis of the sensitive coordination bonds, the stored bio-entities may be released from solution triggered by pH value or other factors. In 2015, Falcaro et al. demonstrated that monocrystalline ZIF-8 can take up proteins, enzymes, and DNA [104

Hierarchical Bi₂WO₆/TiO₂-nanotube composites derived from natural cellulose for visible-light photocatalytic treatment of pollutants

• Zehao Lin,
• Zhan Yang and
• Jianguo Huang

Beilstein J. Nanotechnol. 2022, 13, 745–762, doi:10.3762/bjnano.13.66

• corresponding Cr(VI) pollutant solution. In addition, the pH values (2, 3, 4, and 5) of the initial Cr(VI) pollutant solution were adjusted using the H2SO4 (0.1 M) aqueous solution. In order to obtain the photocatalytic performances of the samples, the removal percentage of Cr(VI) and degradation percentage of

• hierarchical Bi2WO6/TiO2-NT nanocomposites. It is reported that the pH value of the Cr(VI) pollutant solution has an important influence in the photocatalytic reduction of Cr(VI) [53]. In order to investigate the photocatalytic reduction activities of the samples toward Cr(VI), the 70%−Bi2WO6/TiO2-NT

• nanocomposite was set as the representative photocatalyst for the exploration of optimal pH values of the Cr(VI) pollutant solution under visible-light irradiation. It was demonstrated that the reduction efficiency of Cr(VI) under the alkaline condition was poor because the newly formed Cr(OH)3 precipitates

A nonenzymatic reduced graphene oxide-based nanosensor for parathion

• Sarani Sen,
• Anurag Roy,
• Ambarish Sanyal and
• Parukuttyamma Sujatha Devi

Beilstein J. Nanotechnol. 2022, 13, 730–744, doi:10.3762/bjnano.13.65

• monitoring of PT. For this purpose, the electrochemical reduction of GO was tuned using various electrolytic buffers with different pH values, supporting the variation of the physicochemical characteristics of ERGO discussed in this work. Besides, this study highlights the scope of an interference-free

• nonenzymatic approach through electrochemical nanosensing which can also be used in other biosensing applications. Experimental Chemicals The chemicals used in this work are summarized in Supporting Information File 1, Table S1. Sodium dihydrogen phosphate was used to prepare phosphate buffer saline (pH 4.6

• , 7.4, 9). Acetate buffer (20 mM, pH 4.5), and Britton–Robinson (BR) buffer (40 mM, pH 4) consisting of phosphoric acid, boric acid, and acetic acid were also prepared. Synthesis of graphene oxide Graphene oxide was synthesized from graphite powder using a modified Hummer’s method [30][31]. In detail

Design and selection of peptides to block the SARS-CoV-2 receptor binding domain by molecular docking

• Kendra Ramirez-Acosta,
• Ivan A. Rosales-Fuerte,
• J. Eduardo Perez-Sanchez,
• Alfredo Nuñez-Rivera,
• Josue Juarez and
• Ruben D. Cadena-Nava

Beilstein J. Nanotechnol. 2022, 13, 699–711, doi:10.3762/bjnano.13.62

• , peptides with great affinity to the RBD were selected. The most common amino acids involved in the recognition of the RBD were identified to design novel peptides based on the number of hydrogen bonds that were formed. At physiological pH, these peptides are almost neutral and soluble in aqueous media

• temporin B and lysozyme (61–80). The net charge calculated for the OAPs varies according to the number of negatively and positively charged amino acids present in the primary structure. The net charge values are in the range of −3.9 to 2.9 at pH 7. The OAPs were selected based on an absolute value of the

• electrical net charge smaller than 3.9 (|charge| ≤ 3.9, which is the net charge of ACE2), to avoid possible cytotoxic effects [54][55]. Given that, at physiological pH, the RBD active region is positively charged, it could be assumed that negatively charged peptides, such as sesquin and MVL (74–87) (Figure

Sodium doping in brookite TiO₂ enhances its photocatalytic activity

• Boxiang Zhuang,
• Honglong Shi,
• Honglei Zhang and
• Zeqian Zhang

Beilstein J. Nanotechnol. 2022, 13, 599–609, doi:10.3762/bjnano.13.52

• . Then 1.5 mL of TBOT was slowly dropped into the solution to form a transparent yellow sol by vigorously stirring for a full reaction between TBOT and oxalic acid. The pH value of the sol was adjusted to 10 by using 2 mol/L of NaOH solution. After stirring for another 1 h, the sol was transferred into a

• 100 mL Teflon-lined autoclave and heated at 180 °C for 8 h. The white precipitate was collected by centrifugation (8000 rpm, 10 min), washed to a neutral pH with distilled water and absolute ethanol, and then dried at 80 °C. To inspect the effect of the calcinating temperature on the structure of the

A new method for obtaining the magnetic shape anisotropy directly from electron tomography images

• Cristian Radu,
• Ioana D. Vlaicu and
• Andrei C. Kuncser

Beilstein J. Nanotechnol. 2022, 13, 590–598, doi:10.3762/bjnano.13.51

• nanoparticle system. Experimental For the preparation of the magnetite MNPs, the following starting materials were used as purchased: FeSO4·7H2O (Merck, 99.5%), hexadecyltrimethylammonium bromide (CTAB, 99+%, Acros Organics), NaOH (puriss p.a., ACS reagent, reag. Ph. Eur., K < 0.02%, ≥98%, pellets), NH4OH (for

Detection and imaging of Hg(II) in vivo using glutathione-functionalized gold nanoparticles

• Gufeng Li,
• Shaoqing Li,
• Rui Wang,
• Min Yang,
• Lizhu Zhang,
• Yanli Zhang,
• Wenrong Yang and
• Hongbin Wang

Beilstein J. Nanotechnol. 2022, 13, 549–559, doi:10.3762/bjnano.13.46

• mentioning here that the pH value of the reaction systems played an important role in the synthesis of GSH-Rh6G2. Rh6G2, as an ideal candidate for controlled-release molecular systems, shows little fluorescence (Figure 1b). In the absence of GNPs, the conjugation of GSH-Rh6G2 yields obvious fluorescence. The

• S1, Supporting Information File 1) [42]. The final product of the reaction between Rh6G2 and GSH was proved by TOF-MS analysis (Figure S2, Supporting Information File 1). By adjusting the pH value from an unadjusted slightly acidic environment to pH 7, a significant decrease in the fluorescence of

• first six hours as shown in Figure 4a. Furthermore, the pH value is critical regarding the fluorescence intensity. GNPs-GSH-Rh6G2 displayed a large change in the fluorescence intensity in the pH range from 1 to 5 (Figure 4b). This indicates that Rh6G2 tends to be protonated at low pH values, which

Stimuli-responsive polypeptide nanogels for trypsin inhibition

• Petr Šálek,
• Jana Dvořáková,
• Sviatoslav Hladysh,
• Diana Oleshchuk,
• Ewa Pavlova,
• Jan Kučka and
• Vladimír Proks

Beilstein J. Nanotechnol. 2022, 13, 538–548, doi:10.3762/bjnano.13.45

• biocompatible Nα-ʟ-lysine-grafted α,β-poly[(2-propyne)-ᴅ,ʟ-aspartamide-ran-(2-hydroxyethyl)-ᴅʟ-aspartamide-ran-(2-(4-hydroxyphenyl)ethyl)-ᴅʟ-aspartamide] (Nα-Lys-NG). Both nanogels were prepared by HRP/H2O2-mediated crosslinking in inverse miniemulsions with pH and temperature-stimuli responsive behavior

• acid-labile cholesteryl-modified pullulan nanogel that formed a complex with loaded bovine serum albumin and released it under acidic conditions [17]. Landfester et al. used a bio-orthogonal reaction to fabricate a dextran nanogel with pH-responsive hydrazine linkages allowing for a controlled release

• biodegradable PHEG-Tyr and biocompatible and non-biodegradable Nα-Lys-NG polypeptide precursors by HRP/H2O2-mediated crosslinking in inverse miniemulsion for the delivery of AAT. Both prepared polypeptide nanogels demonstrate stimuli-responsive behavior under different pH values and temperatures. After

Influence of thickness and morphology of MoS₂ on the performance of counter electrodes in dye-sensitized solar cells

• Lam Thuy Thi Mai,
• Hai Viet Le,
• Ngan Kim Thi Nguyen,
• Van La Tran Pham,
• Thu Anh Thi Nguyen,
• Nguyen Thanh Le Huynh and
• Hoang Thai Nguyen

Beilstein J. Nanotechnol. 2022, 13, 528–537, doi:10.3762/bjnano.13.44

• exhibited two redox couple peaks at −0.34 V/−0.76 V and −0.77 V/−1.34 V attributed to the redox reactions of Mo7O246− and MoO42− ions, respectively [27]. The presence of MoO42− ions is due to the equilibrium in Equation 3, which occurs in acidic solution of (NH4)6Mo7O24 (the pH here is about 4.3). The CV

• ) and Na2S in acidic media (adjusted to pH 6) is very favorable to the preparation of MoS42− precursor solution. In this work, the optimal concentration ratio of (NH4)2Mo7O24 (mM) to Na2S (g/L) was found to be 1:6 (data not shown). It can be seen from the CV curve of the mixture solution that the

• )6Mo7O24 (x mM) and Na2S (y g·L−1) in distilled water, the pH of the solution was adjusted to 6.0 using a 20% (v/v) H2SO4 solution, KCl (0.1 M) was used as the supporting electrolyte. The concentration ratio between (NH4)2Mo7O24 and Na2S was kept constant (x/y = 1:6) with different concentration levels