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Rapid detection and discrimination of pathogenic bacteria for food safety, environmental pollution, medical diagnoses, and chemical and biological threats remains a considerable challenge. In the present work, we demonstrate positively charged Ag/Au bimetallic nanoparticles (Ag/Au bmNPs) as a potential surface-enhanced Raman scattering (SERS) substrate for label-free detection and discrimination of three bacteria, viz., Escherichia coli, Salmonella typhimurium, and Bacillus subtilis with excellent reproducibility. The approach relies on a priori synthesis of Ag/Au bmNPs and subsequent SERS studies on bacteria. The positive surface charge on Ag/Au bmNPs offers significant advantages of short acquisition time at very low power, high sensitivity, and a simple operating procedure without the need of very specific procedures or protocols used to capture the bacteria. The reproducible and specific intrinsic fingerprint of the cell wall and intracellular components of three bacteria obtained by label-free SERS enables precise discrimination and classification of three bacteria using multivariate analyses such as principal component analysis and canonical discriminant analysis.

Polyacenes, such as anthracene, tetracene, pentacene etc., have been identified as potential candidates for singlet fission (SF) and triplet-triplet annihilation (TTA) processes in their crystalline and thin film forms as they possess significant singlet and triplet exciton couplings. Interestingly, phenyl-ethynyl substitution to anthracene at the 9,10 positions (9,10-bis(phenylethynyl)anthracene/BPEA) enhances the transverse pi-electron conjugation and retains the planar structure even in the excited state. The excited singlet state S-1 and the multi-excitonic state (1)(TT) in BPEA are separated by similar to 30 meV (similar to 250 cm(-1)) making it an ideal system for both SF and TTA applications. BPEA is very effective in photon up-conversion even for low input intensities. Transient absorption measurements of BPEA in n-hexane solution are inadequate for distinguishing the S-1 state and the multi-excitonic state (1)(TT), since the spectroscopic features are complex (mixed) due to the isoenergetic nature and the existence of an equilibrium between these states. However, ultra fast Raman loss spectroscopy reveals a systematic red shift and a blue shift in the central frequencies of the Raman modes corresponding to C C and C C vibrational frequencies with time constants of similar to 2.0 and similar to 20 ps, respectively. Such a shift in the Raman frequencies is direct evidence of the structural changes that take place while changing from excited singlet state S-1 to the multi-excitonic state on the potential surface.

Polyacenes, such as anthracene, tetracene, pentacene etc., have been identified as potential candidates for singlet fission (SF) and triplet-triplet annihilation (TTA) processes in their crystalline and thin film forms as they possess significant singlet and triplet exciton couplings. Interestingly, phenyl-ethynyl substitution to anthracene at the 9,10 positions (9,10-bis(phenylethynyl)anthracene/BPEA) enhances the transverse pi-electron conjugation and retains the planar structure even in the excited state. The excited singlet state S-1 and the multi-excitonic state (1)(TT) in BPEA are separated by similar to 30 meV (similar to 250 cm(-1)) making it an ideal system for both SF and TTA applications. BPEA is very effective in photon up-conversion even for low input intensities. Transient absorption measurements of BPEA in n-hexane solution are inadequate for distinguishing the S-1 state and the multi-excitonic state (1)(TT), since the spectroscopic features are complex (mixed) due to the isoenergetic nature and the existence of an equilibrium between these states. However, ultra fast Raman loss spectroscopy reveals a systematic red shift and a blue shift in the central frequencies of the Raman modes corresponding to C C and C C vibrational frequencies with time constants of similar to 2.0 and similar to 20 ps, respectively. Such a shift in the Raman frequencies is direct evidence of the structural changes that take place while changing from excited singlet state S-1 to the multi-excitonic state on the potential surface.

In this work, we report the phase transition behavior of hydrogenated amorphous silicon on the application of nanosecond timescale high-field pulse electrical stress. The transition of amorphous silicon to nanocrystalline silicon, confirmed through Raman spectroscopy, is marked by an abrupt change in the pulse I-V characteristics. The mechanism of the phase transition at high electric field involving the avalanche generation of charge carriers and optical phonon generation is discussed. The role of defect states in optical phonon localization and eventual phase transition is explored. The phase transition in the case of devices with a drain-gate underlap is also studied. The role of self-heating in accelerating the phase transition has also been explored. The impact of channel dimensions on the onset of the phase transition is also discussed. Characterization of the resultant nc-Si is done through deconvolution of the Raman spectra, and the quality of nc-Si created is found comparable to earlier studies.

In this work, we report a facile one-spot synthesis process and the influence of compositional variation on the electrochemical performance of Ni-Mn-oxides (Ni:Mn = 1:1, 1:2, 1:3, and 1:4) for high-performance advanced energy storage applications. The crystalline structure and the morphology of these synthesized nanocomposites have been demonstrated using X-ray diffraction, field emission scanning electron microscopy, and transmission electron Microscopy. Among these materials, Ni-Mn-oxide with Ni:Mn = 1:3 possesses a large Brunauer-Emmett-Teller specific surface area (127 m(2) g(-1)) with pore size 8.2 nm and exhibits the highest specific capacitance of 1215.5 F g(-1) at a scan rate 2 mV s(-1) with an excellent long-term cycling stability (similar to 87.2% capacitance retention at 10 A g(-1) over 5000 cycles). This work also gives a comparison and explains the influence of different compositional ratios on the electrochemical properties of Ni-Mn-oxides. To demonstrate the possibility of commercial application, an asymmetric supercapacitor device has been constructed by using Ni-Mn-oxide (Ni:Mn = 1:3) as a positive electrode and activated carbon (AC) as a negative electrode. This battery-like device achieves a maximum energy density of 132.3 W h kg(-1) at a power density of 1651 W kg(-1) and excellent coulombic efficiency of 97% over 3000 cycles at 10 A g(-1).

Separating the particles from the liquid component of sample solutions is important for several microfluidic-based sample preparations and/or sample handling techniques, such as plasma separation from whole blood, sheath-free flow focusing, particle enrichment etc. This paper presents a microfluidic in-flow decantation technique that provides the separation of particles from particle-free fluid while in-flow. The design involves the expansion of sample fluid channel in lateral and depth directions, thereby producing a particle-free layer towards the walls of the channel, followed by gradual extraction of this particle-free fluid through a series of tiny openings located towards one-end of the depth-direction. The latter part of this design is quite crucial in the functionality of this decantation technique and is based on the principle called wee-extraction. The design, theory, and simulations were presented to explain the principle-of-operation. To demonstrate the proof-of-principle, the experimental characterization was performed on beads, platelets, and blood samples at various hematocrits (2.5%-45%). The experiments revealed clog-free separation of particle-free fluid for at least an hour of operation of the device and demonstrated purities close to 100% and yields as high as 14%. The avenues to improve the yield are discussed along with several potential applications.

Surface electrode switching of 16-electrode wireless EIT is studied using a Radio Frequency (RF) based digital data transmission technique operating with 8 channel encoder/decoder ICs. An electrode switching module is developed the analog multiplexers and switched with 8-bit parallel digital data transferred by transmitter/receiver module developed with radio frequency technology. 8-bit parallel digital data collected from the receiver module are converted to 16-bit digital data by using binary adder circuits and then used for switching the electrodes in opposite current injection protocol. 8-bit parallel digital data are generated using NI USB 6251 DAQ card in LabVIEW software and sent to the transmission module which transmits the digital data bits to the receiver end. Receiver module supplies the parallel digital bits to the binary adder circuits and adder circuit outputs are fed to the multiplexers of the electrode switching module for surface electrode switching. 1 mA, 50 kHz sinusoidal constant current is injected at the phantom boundary using opposite current injection protocol. The boundary potentials developed at the voltage electrodes are measured and studied to assess the wireless data transmission.