Protein-encapsulated nanoclusters (NCs) are emerging as a versatile platform for in-vivo imaging and other biomedical applications due to their ultrasmall size and excitation in the near-infrared region. Encapsulation may however affect protein structure, size, charge, and its interaction with lipid membranes. In this study, bulk characterization methods along with surface-sensitive vibrational sum-frequency generation (VSFG) spectroscopy were employed to study the secondary structure of bovine serum albumin (BSA) with blue-emitting Au8NCs at the air/water and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DPPG) lipid/water interfaces. With this approach, the difference in the adsorption behavior between native BSA and BSA with an increasing number of blue-emitting NCs was investigated under different pH conditions. At pH 7, at which both BSA and the lipid are negatively charged, protein molecules are found to associate with the DPPG monolayer via hydrophobic interactions with no preferential orientation across the lipid monolayer. At pH 3, adsorption of BSA at the DPPG monolayer occurs mainly due to electrostatic interactions between the negatively charged lipid headgroups and the positively charged protein, resulting in a uniform orientation of the protein across the lipid monolayer. Complimentary bulk studies by circular dichroism and particle size measurements show that the encapsulation of Au8NCs is associated with the loss of BSA helicity, which makes BSA-encapsulated Au8NCs prone to oligomerization, especially at a high content of Au8NCs at one BSA protein. The results indicate that the hydrodynamic diameter of BSA with Au8NCs strongly depends on the molar fraction of gold, the pH, and the storage time. A prolonged storage of Au8NCs@BSA at pH 7 increases the rate of protein oligomerization.

Efficient oxygen evolution reaction (OER) electrocatalysts are highly desired in the field of water electrolysis and rechargeable metal-air batteries. In this study, a chelate polymer, composed of copper (II) and dithiooxamide, was used to derive an efficient catalytic system for OER. Upon potential sweep in 1 M KOH, copper (II) centers of the chelate polymer were transformed to CuO and Cu(OH) 2 . The carbon-dispersed CuO nanostructures formed a nanocomposite which exhibits an enhanced catalytic activity for OER in alkaline media. The nanocomposite catalyst has an overpotential of 280 mV (at 1 mA/cm 2 ) and a Tafel slope of 81 mV/dec in 1M KOH solution. It has a seven-fold higher current than an IrO 2 /C electrode, per metal loading. A catalytic cycle is proposed, in which CuO undergoes electrooxidation to Cu 2 O 3 that further decomposes to CuO with the release of oxygen. This work reveals a new method to produce an active nanocomposite catalyst for OER in alkaline media using a non-noble metal chelate polymer and a porous carbon. This method can be applied to the synthesis of transition metal oxide nanoparticles used in the preparation of composite electrodes for water electrolyzers and can be used to derive cathode materials for aqueous-type metal-air batteries.Catalysts 2020, 10, 233 2 of 11 overpotential at given current density, though the mass activity (current per metal loading) would be a better descriptor of catalysts efficiency [9,10].In 2014, Liu et al. showed that nanostructured copper oxide films, deposited from copper (II) complexes on a fluorine-doped tin oxide (FTO) electrode can efficiently catalyze OER in alkaline solutions [11]. The overpotential of the catalyst obtained from copper (II) ethylenediamine complex was estimated to be 475 mV at 10 mA/cm 2 . Due to this relatively low overpotential, various copper (II) organic complexes and copper (II) salts were investigated for their activity towards water oxidation. High water oxidation rates were observed for complexes with low electrochemical stability [12]. The enhanced catalytic activity was thus ascribed to CuO particles produced via electrodecomposition of the initial complex. In order to identify catalytically active species, Deng et al. investigated the OER in alkaline solutions on Cu 2 O and CuO films, plated on a Cu disk, from solutions containing CuSO 4 . Cu(III) centers were proposed to be catalytically active species based on the analysis of in situ Raman and X-ray absorption near-edge structure (XANES) results. [5]. These findings motivated researchers to prepare the OER active catalyst by controlling the size, shape and dispersion of copper oxides [13]. Various methods such as hydrothermal, electrochemical and sonochemical can be used to prepare copper oxide nanoparticles [14]. High temperature treatment of CuO films yields particles with the size >200 nm. Such films were found active towards the OER and stable in alkaline solutions, with an overpotential of 430 mV at 1 mA/cm 2 [15]. The drawback of using copper oxides as electroc...

Indonesia is one of the largest rubber producers worldwide. However, rubber seeds still garner less attention due to their low economic value. In fact, the rubber seeds contain 40–50% (w/w) of rubber seed oil (RSO), which is a potential candidate to be used as a feedstock in biodiesel production. In this regard, this study aims to model and simulate the production process of biodiesel from RSO via transesterification reaction, employing methanol and heterogeneous catalyst. The simulation was performed using ASPEN Hysys v11. Acid-based catalyzed esterification was implemented to eliminate soap formation, which may significantly lower biodiesel yield. The results showed that an RSO inlet rate of 1100 L/h with a methanol to oil molar ratio of 1:6 could generate around 1146 L/h biodiesel. Methanol recovery was conducted, an approximately 95% of excess methanol could be regenerated. Simulation results indicated that the properties of the biodiesel produced are compatible with modern diesel engines. Economic analysis also shows that this technology is promising, with excellent investment criteria.

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Cottonseed oil (CSO) is well known as one of the commercial cooking oils. However, CSO still needs to compete with other edible oils available in the market due to its small production scale and high processing cost, which makes it a potential candidate as a feedstock for biodiesel production. To date, transesterification is the most widely applied technique in the conversion of vegetable oil to biodiesel, with glycerol produced as a by-product. Large-scale biodiesel production also implies that more glycerol will be produced, which can be further utilized to synthesize hydrogen via the steam reforming route. Therefore here, an integrated biodiesel and hydrogen production from CSO was simulated using Aspen Hysys v11. Simulation results showed that the produced biodiesel has good characteristics compared to standard biodiesel. An optimum steam-to-glycerol ratio for hydrogen production was found to be 4.5, with higher reaction temperatures up to 750 °C resulting in higher hydrogen yield and selectivity. In addition, a simple economic analysis of this study showed that the integrated process is economically viable.