Identifying dual role electrode materials capable of storing both lithium and sodium are thought to be highly relevant, as these materials could find potential applications simultaneously in lithium and sodium ion batteries. In this regard, the concept of dual alkali storage is demonstrated in Fe(3)O(4) anode material undergoing conversion reaction. To enable improved storage, a rational active material and electrode design is proposed. Accordingly, the following features were simultaneously incorporated into the design: (i) an optimal particle size, (ii) a conducting matrix, (iii) adequately large active material surface area and (iv) strong electrode material-current collector integrity. Electrodes incorporating this rational design exhibit excellent high rate performance and impressive cyclability during lithium storage. For instance, Fe(3)O(4) electrodes deliver a charge capacity of 950 mAh g(-1) at 1.2 C (~2.6 times higher than graphite and 5.4 times higher than Li(4)Ti(5)O(12)). Further, these electrodes show no signs of capacity fade even up to 1100 cycles. Impressively, the cells could also be charged-discharged to 65% of their theoretical capacity in just 5 min or 12 C (11.11 A g(-1)). The rate performance and cyclability of lithium storage achieved here are amongst the highest reported values in the literature for the conversion reaction in Fe(3)O(4). Besides lithium storage, the dual role of this anode is shown by demonstrating its sodium storage ability by conversion reaction for the first time.

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We report here on the lithium storage performance of ␣-and ␥-Fe 2 O 3 , undergoing conversion reaction at C/10 and 2C. Both ␣-and ␥-Fe 2 O 3 transform to nanostructured Fe/Li 2 O composite during the first discharge, while the first charge results in the formation of nanosized ␥-Fe 2 O 3 . Such a transition from ␣-Fe 2 O 3 to ␥-Fe 2 O 3 is attributed to its thermodynamics at the nanosize. Better storage performance of ␥-Fe 2 O 3 at 2C compared with ␣-Fe 2 O 3 is attributed to the formation of highly crystalline, nanosized ␥-Fe 2 O 3 . Apart from the reported inherent electronic conductivity of ␣-Fe 2 O 3 , the thermodynamics at the nanosize is also found to be one of the rate-limiting factors.

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Band bending assisted fluorescence sensing of glucose and bovine serum albumin using MoS2 quantum dots.