In recent years there is an increasing demand for the prepara-tion of free-standing conducting polymer films as they can provide new opportunities in several applications such as understanding of fundamental mechanical or electrical properties, chemical or biosensors, ion-exchange membranes, organic electronics, polymeric batteries, artificial muscles, etc. 1, 2 Among various conducting polymers, polypyrrole (PPy) is widely sought after due to its excellent stability under environmental conditions, good conductivity, and biocompatibility. 3 The free-standing PPy films have mainly been prepared by following two methods:(i) deposition onto the substrates by electropolymerization or spin-coating, followed by peeling the films off the substrates, 4À6 and (ii) segregating the PPy films prepared at liquid/liquid interface, ie, chloroform/water along with (NH4) 2S2O8, an oxidant. 7 The first approach either requires complicated equipment or suffers from damage during the transfer process, especially for nanometer-thick, large-area films. Similar problems occur while segregating the films grown at liquid/liquid interfaces. Very recently, ultrathin free-standing PPy films have also been prepared at an air/ionic liquid interface through interface oxypolymerization. 8 In this Communication, we report a novel one-pot fabrication strategy for the growth of free-standing PPy nanosheets. In our process spontaneously formed 5-(4-hydroxyphenyl)-10, 15, 20-triphenylporphyrin (TPPOH) J-aggregate films at the air/aqueous FeCl3 interface acts as an in-situ template for the growth of PPy nanosheets. Pyrrole (98%) was procured from Aldrich and distilled over calcium hydride under reduced pressure prior to use. Anhydrous FeCl3 (LR grade) was purchased from Thomas Baker. The organic solvents used were of analytical grade, and Millipore water was used for washing and solution preparation. The TPPOH was synthesized using the procedure reported earlier. 9 The typical process employed for the growth of free-standing PPy films is as follows. In a beaker, 60 mL of 0.1 M aqueous FeCl3 was taken, and in a steady state, a 200 μL solution consisting of 1 mM TPPOH and 0.01 À1 M pyrrole prepared in dichloromethane (DCM) was slowly dropped using a micropipette. In addition, pure TPPOH and PPy films were prepared by dropping respectively 1 mM TPPOH or 0.1 M pyrrole solutions into FeCl3. In all the cases, films were spontaneously formed at the air/FeCl3 interface. Pure TPPOH films were formed within 5 min, while formation of pure PPy films took more than 20 min. All the films were mechanically strong and were lifted easily onto glass substrates. Prior to the characterization, all the films were thoroughly rinsed using Millipore water. Since TPPOH dissolves in DCM, therefore TPPOH/PPy bilayers were washed using DCM to obtain free-standing PPy films. The formation kinetics of TPPOH/PPy bilayer films was studied by lifting them onto glass substrates from an air/FeCl3 interface after various time intervals and washing them using DCM. It was found that no residue was left on glass substrates for films lifted after e10 min, and it is only after this period, PPy films were left on the glass substrate. These results indicated that while TPPOH film is formed very quickly, the kinetics of interfacial polymerization of PPy is rather slow. The PPy films prepared without and with TPPOH would hereafter be referred as PPy-1 and PPy-2, respectively. These films were characterized by UVÀvis spectroscopy (Jasco) and Fourier-transform infrared spectroscopy (Bruker 80 V). Surface morphology of the films was imaged using scanning electron microscopy (SEM)(TESCAN, TS5130MM). The …