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Silicon compatible wafer scale MoS2 heterojunctions are reported for the first time using colloidal quantum dots. Size dependent direct band gap emission of MoS2 dots are presented at room temperature. The temporal stability and decay dynamics of excited charge carriers in MoS2 quantum dots have been studied using time correlated single photon counting spectroscopy technique. Fabricated n-MoS2/p-Si 0D/3D heterojunctions exhibiting excellent rectification behavior have been studied for light emission in the forward bias and photodetection in the reverse bias. The electroluminescences with white light emission spectra in the range of 450–800 nm are found to be stable in the temperature range of 10–350 K. Size dependent spectral responsivity and detectivity of the heterojunction devices have been studied. The peak responsivity and detectivity of the fabricated heterojunction detector are estimated to be ~0.85 A/W and ~8 × 1011 Jones, respectively at an applied bias of −2 V for MoS2 QDs of 2 nm mean diameter. The above values are found to be superior to the reported results on large area photodetector devices fabricated using two dimensional materials.

The COVID-19 outbreak due to SARS-CoV-2 has raised several concerns for its high transmission rate and unavailability of any treatment to date. Although major routes of its transmission involve respiratory droplets and direct contact, the infection through faecal matter is also possible. Conventional sewage treatment methods with disinfection are expected to eradicate SARS-CoV-2. However, for densely populated countries like India with lower sewage treatment facilities, chances of contamination are extremely high; as SARS-CoVs can survive up to several days in untreated sewage; even for a much longer period in low-temperature regions. With around 1.8 billion people worldwide using faecal-contaminated source as drinking water, the risk of transmission of COVID-19 is expected to increase by several folds, if proper precautions are not being taken. Therefore, preventing water pollution at the collection/distribution/consumption point along with proper implementation of WHO recommendations for plumbing/ventilation systems in household is crucial for resisting COVID-19 eruption.

Highly luminescent MoS 2 nanocrystals (NCs) with controlled size distribution have been achieved using a simple yet inexpensive and impurity free sono-chemical exfoliation method followed by gradient centrifugation. The size of nanocrystals could be varied within the diameter range of ∼4 to 70 nm. Typical MoS 2 nanocrystal has exhibited high crystalline quality with 0.25 nm lattice fringe spacing for (002) planes for 2-H phase of MoS 2 . Raman spectra has revealed that both out-of-plane and in-plane vibrational modes are stiffen due to the edge effect of MoS 2 NCs. The size tunable optical properties of MoS 2 NCs have been investigated by optical absorption and photoluminescence spectroscopy. The coexistence of direct band gap emission from 2D MoS 2 nanosheets and quantum confined nanocrystals has been achieved. A strong and tunable photoluminescence (560−518 nm) emission due to the quantum size effect of tiny NCs below a critical dimension is reported for the first time. The photocurrent measurement of the Au/MoS 2 −NCs/Au junction has been performed at room temperature to investigate the optical responsivity and switching characteristics, demonstrating the potential of MoS 2 nanocrystals for next generation photonic devices.

Nanospindle and nanorhombohedron and nanocube structured α-Fe2O3 was synthesized by the solvothermal method. An intermixing of ethylenediamine (EN) either with ethanol (EtOH) or water in different volume ratios (either 15:85, 50:50 or 85:15 in particular) was used to generate the structural forms of α-Fe2O3. The study showed that, during synthesis, EN functioned as a ligand and facilitated the growth of nanostructured samples. The probable growth mechanism is discussed in this paper. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) investigations revealed that the nanostructures were formed through oriented attachment of primary nanocrystals. Fourier transform infrared spectroscopy (FTIR) results showed the presence of Fe–O or Fe–O–Fe vibrational bands whereas UV–vis–NIR optical absorbance spectra showed two prominent absorption bands around 540–560 and 670–680 nm. The room temperature magnetization measurement revealed that the remanence and coercivity depend on the morphological attributes of the nanocrystals. The magnetic hysteresis measurement also revealed that α-Fe2O3 nanostructures displayed weak ferromagnetic behaviour at room temperature.

Phase pure rutile SnO2 nanoparticles and nanorods were prepared by solvothermal technique. The diameters of the nanoparticles were in the range of 5–10nm while the length and width of the nanorods were within 100–200nm and ∼50nm, respectively. The crystal structure, morphology, and sizes of the SnO2 nanocrystals were determined by x-ray diffraction and transmission electron microscopy. Optical properties of the products were explored by Fourier transform infrared spectroscopy, optical absorption, photoluminescence, and Raman studies. Size dependent blueshift of the optical band gap of the nanocrystals was observed due to quantum confinement. The photoluminescence spectra showed broad UV emission. The influence of the particle size and the morphology of the SnO2 nanocrystals on the vibration band in the Raman scattering was studied.

Successful realization of various BioMEMS devices demands effective surface modification techniques of PDMS elastomer. This paper presents a detailed report on a simple and cost effective approach for surface modification of PDMS films involving wet chemical treatment in two-step processes: primarily involving piranha solution followed by KOH dip to improve hydrophilicity and stability of PDMS surface. Chemical composition of the solution and surface treatment condition have been varied and optimized to significantly increase the surface energy. The effect of surface modification of the elastomer after wet chemical treatment is analyzed using contact angle measurement and FTIR-ATR study. PDMS surface treated in piranha solution with H 2 O 2 and H 2 SO 4 in the ratio of 2 : 3 followed by a dip in KOH solution for 15 min duration each, demonstrated a maximum reduction of contact angle to ∼27• as compared to untreated sample having a contact angle of ∼110• . The removal of hydrophobic methyl group from elastomer surface and subsequent hydrophilization of surface by wet chemical process was confirmed from FTIR-ATR spectra. This result is also supported by improved adhesion and electrical continuity of deposited aluminum metal film over the modified PDMS surface.