We report an easy synthesis of highly branched gold particles through a seed-mediated growth approach in the presence of citrate. The addition of citrate in the growth solution is found to be crucial for the formation of these branched gold particles. Their size can be varied from 47 to 185 nm. The length of the thumb-like branch is estimated to be between about 5 and 20 nm, and changes slightly as the particle size increases. Owing to these obtuse and short branches, their surface plasmon resonance displays a marked red-shift with respect to the normal spherical particles. These branched gold particles exhibit stronger SERS activity than the non-branched ones, which is most likely related to these unique branching features.
The unique strategy for electrochemiluminescence (ECL) sensor based on the quantum dots (QDs) oxidation in aqueous solution to detect amines is proposed for the first time. Actually, there existed two QDs ECL peaks in anhydrous solution, one at high positive potential and another at high negative potential. However, here we introduced the QDs oxidation ECL in aqueous solution to fabricate a novel ECL sensor. Such sensor needed only lower positive potential to produce ECL, which could prevent the interferences resulted from high potential as that of QDs reduction ECL in aqueous solution. Therefore, the present work not only extended the QDs oxidation ECL application field from anhydrous to aqueous solution but also enriched the variety of ECL system in aqueous solution. Furthermore, we investigated the QDs oxidation ECL toward different kinds of amines, and found that both aliphatic alkyl and hydroxy groups could lead to the enhancement of ECL intensity. Among these amines, 2-(dibutylamino)ethanol (DBAE) is the most effective one, and accordingly, the first ECL sensing application of the QDs oxidation ECL toward DBAE is developed; the as-prepared ECL sensor shows wide linear range, high sensitivity, and good stability.
Here we present a facile one-pot method to prepare high-quality CdTe nanocrystals in aqueous phase. In contrast to the use of oxygen-sensitive NaHTe or H2Te as Te source in the current synthetic methods, we employ more stable sodium tellurite as the Te source for preparing highly luminescent CdTe nanocrystals in aqueous solution. By selecting mercaptosuccinic acid (MSA) as capping agent and providing the borate-citrate acid buffering solution, CdTe nanocrystals with high quantum yield (QY >70% at pH range 5.0–8.0) can be conveniently prepared by this method. The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd2+ to Na2TeO3 on the QY of CdTe nanocrystals was systematically investigated in our experiments. Under optimal conditions, the QY of CdTe nanocrystals is even high up to 83%. The biological application of luminescent MSA-CdTe to HEK 293 cell imaging was also illustrated.
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