Gold Bulletin最新文献

Abstract

Abstract

Healthy dairy products should be free of any substances that threaten human health. However, the use of antibiotics for the treatment of lactating animals can be a risk to human health, as their residues and metabolites can be transferred into milk. Various methods are used to ensure the purity of milk. In this study, a kit based on a specific penicillin aptamer bonded to gold nanoparticles was designed to measure penicillin in milk, and its measurement was performed using ELISA colorimetric method. After synthesis of gold nanoparticles, the molarity of gold nanoparticles was calculated by UV spectrophotometer, and its synthesis was confirmed by FTIR. Salt concentrations were also optimized to bind aptamer to gold nanoparticles. The gold nanoparticles were then bonded to the specific aptamer of penicillin, and the concentration of penicillin G in the milk sample was measured by a biosensor designed by ELISA. The choice of biosensor was also examined in the presence of similar antibiotics.

Conjugation and characterization of poly-ethylene–glycol (PEG)-functionalized gold nanourchin (GNU) with breast cancer biomarker HER-II monoclonal antibody (mAb) (i.e., anti-HER-II) for selective targeting are described. After the functionalization of GNU with PEG, the surface plasmon resonance (SPR) peak was red-shifted, indicating the increase in the hydrodynamic size of the GNU. The Fourier-transform near-infrared spectroscopy (FT-NIR) second derivative result of GNU-PEG provided overtone and combination bands of fundamental vibrational modes of protein molecular structures between 4000 and 7500 cm⁻¹. This mainly included C–H combination and CH₂ bonds, O–H first stretch overtones, the C–H first stretch overtone, and the CH₂ combination first overtone. The UV–Vis absorbance showed a strong absorption of light at 227 and 275 nm corresponding to tyrosine peaks. The fluorescence emission peak at 315 nm corresponds to Stokes shift when excited by 280 nm corresponding to tyrosine in the mAb, and the peak at 497 nm likely corresponds to alanine. After conjugation of GNU-PEG with mAb, the FT-NIR indicated the bands corresponding to NH₂ combination and amino acids, first overtone symmetric and antisymmetric OH stretching, C–H combination, and the second overtones and combination modes. Surface-enhanced Raman scattering (SERS) provided useful information on the molecular structure and composition of the sample within 300–3500 cm⁻¹. The intensity behavior of SERS signals exhibited a statistical nature due to Brownian fluctuating movement. In addition, the intensity and number of SERS lines varied with the laser power. The dominant peaks were corresponding to histidine, tyrosine, tryptophan, phenylalanine, and C–H, N–H, C–N, and O–H bonds.

Abstract

Gold nanorods are of great significance in biomedical and sensing applications due to their local surface plasmon resonance absorption. The silver-mediated seeding method was used to prepare gold nanorods, the longitudinal local surface plasmon resonance (LSPR) absorption of the prepared gold nanorods was monitored, and the growth kinetics of the gold nanorods were discussed. The results show that the growth process of gold nanorods is characterized by a first-order reaction, and its activation energy is about 54.4 kJ/mol. This experimental conclusion provides a good theoretical guide for the preparation of gold nanorods during application research.

The age hardenability of 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) alloyed with Ti at various concentrations (0.5, 0.75, and 1 wt.%) was studied. The addition level of Ti is compensated with Ag to maintain the purity of gold in 22 karat, i.e., 91.75 wt.%. The Ti containing 22 karat gold was prepared by melting Au, Cu, and Ag and adding Ti via Au-6wt.%Ti master alloy. The castings obtained were cold-rolled into thin sheet (90% reduction). Both the cast and cold-rolled sheets were subjected to age hardening treatment (solutionizing and artificial aging). Artificial aging was performed as a function of time at 550 °C to identify the peak aging. At all addition level of Ti, the 22 karat gold responded well to the age hardening treatment. The cold-worked sheet samples showed faster peak aging within 30 min. and higher peak hardness than their cast counterpart. Increasing the Ti concentration increases the peak hardness of both cold-rolled sheet and casting samples. Transmission electron microscopic analysis of the peak aged cold-rolled sheet samples shows uniformly distributed coherent Au₄Ti precipitates in Au matrix which contribute to the higher hardness.

The present study attempted to analyse the random-walk characteristics of the gold spot price of the London Bullion Market Association (LBMA) by using several linear and nonlinear models. The research collects two decades of daily data from 3rd February 2000 to 2nd October 2020. Econometric tests such as serial correlation test, unit-root tests, multiple variance ratio (MVR), and the BDS test were applied to examine the linear and nonlinear dependence of return series. Further, we employed all the tests from ARCH family to examine the volatility clustering of the gold return series. The results of serial correlation and the unit-root test suggest that the gold return is stationary, therefore does not follow the random-walk benchmark, and hence the gold market is inefficient. EGARCH results indicate that the positive news has a more significant impact on the gold return than the negative news. The findings have important implications for the efficient portfolio investments, and better hedging opportunities for the investors.

In 2009, a metal detectorist discovered a hoard of Anglo-Saxon gold and silver in a field in Staffordshire. Hence, it quickly became known as ‘The Staffordshire Hoard’. It was, and remains, the biggest collection of Anglo-Saxon gold (4 kg) and silver (1.7 kg) ever discovered and comprised of more than 4000 fragments that equated to over 600 discrete objects and larger pieces. The Staffordshire Hoard is co-owned by Birmingham and Stoke-on-Trent City Councils and is cared for on behalf of the nation by Birmingham Museums Trust and The Potteries Museum & Art Gallery. Over the intervening years, most of the larger and recognisably important pieces have now been identified and catalogued. We now also know an exceptional amount about their probable methods of manufacture, artistic styles, date, and function. This paper focuses on what is now known to be one of the most fragmented yet magnificent of its objects, a Helmet that has been declared as being ‘fit for a king’, but which was found scattered into well over 1000 disparate fragments. Fragments that  are now considered to make up around one-third of the Hoard’s total of finds and compose this single high-status Golden Helmet. Too damaged and incomplete to be re-joined or displayed in a form that delivers to the casual observer a true sense of the majesty of the original. Thus, the museums responsible for the collection commissioned an experimental reconstruction project to create two of the helmets for display in their shared Hoard collections.