Depanjan Sarkar

Microplastics (MPs) and per‐ and polyfluoroalkyl substances (PFAS) co‐occur in natural and drinking waters, where they persist, accumulate, and pose risks to ecological and human health. Their mitigation demands integrated detection and remediation beyond single‐function platforms. Here, we report Ag@TiO ₂ nanobrushes (NBs), fabricated entirely by ambient charged microdroplet deposition, as a unified substrate for MP capture, SERS‐based sensing, and photocatalytic PFAS degradation. In a two‐step electrospray process, 1D Ag nanowire arrays (Ag NBs) were grown over large areas and overcoated with TiO ₂ . During overcoating, a Marangoni‐type capillary rearrangement drives Ag nanoparticles to the wire periphery, yielding an Ag@TiO ₂ architecture with a percolated plasmonic network in a photoactive TiO ₂ scaffold. The 3D NB network traps MP beads, while dense electromagnetic 3D hotspots enable SERS detection of Rhodamine 6G (LOD ∼38 fM; EF ∼6 × 10 ⁷ ) and 1 µm polystyrene beads (LOD ∼31.6 ng mL ⁻¹ ; EF ∼ 10 ⁵ ) across DI, tap, and simulated seawater. The unmodified substrate drives photocatalytic degradation of perfluorooctanoic acid under ambient sunlight, confirmed by mass spectrometry. This is the first fully electrosprayed platform, integrating MP trapping, femtomolar‐level SERS detection, and PFAS photoremediation, thereby demonstrating ambient charged microdroplets as a scalable route to multifunctional nanostructures for water monitoring and remediation.

SDS-enriched microdroplets create an electron-rich interface that enhances the reduction reaction.

Ultrasonic nebulization-assisted transformation of copper acetate monohydrate to tenorite (CuO).

The creation of micrometer‐sized sheets of silver at the air–water interface by direct deposition of electrospray‐generated silver ions (Ag ⁺ ) on an aqueous dispersion of reduced graphene oxide (RGO), in ambient conditions, is reported. In the process of electrospray deposition (ESD), an electrohydrodynamic flow is created in the aqueous dispersion, and the graphene sheets assemble, forming a thin film at the air–water interface. The deposited Ag ⁺ coalesce to make single‐crystalline Ag sheets on top of this assembled graphene layer. Fast neutralization of Ag ⁺ forming atomic Ag, combined with their enhanced mobility on graphene surfaces, presumably facilitates the growth of larger Ag clusters. Moreover, restrictions imposed by the interface drive the crystal growth in 2D. By controlling the precursor salt concentration, RGO concentration, deposition time, and ion current, the dimensionality of the Ag sheets can be tuned. These Ag sheets are effective substrates for surface‐enhanced Raman spectroscopy (SERS), as demonstrated by the successful detection of methylene blue at nanomolar concentrations.

Parkinson’s disease (PD) is the second most common neurodegenerative disorder and identification of robust biomarkers to complement clinical diagnosis will accelerate treatment options. Here we demonstrate the use of direct infusion of sebum from skin swabs using paper spray ionisation coupled with ion mobility mass spectrometry (PS-IM-MS) to determine the regulation of molecular classes of lipids in sebum that are diagnostic of PD. A PS-IM-MS method for sebum samples that takes three minutes per swab was developed and optimised. The method was applied to skin swabs collected from 150 people and elucidates ~ 4200 features from each subject which were independently analysed. The data included high molecular weight lipids (>600 Da.) that differ significantly in the sebum of people with PD. Putative metabolite annotations of several lipid classes, predominantly triglycerides and larger acyl glycerides, were obtained using accurate mass, tandem mass spectrometry and collision cross section measurements.

We introduce a new and simple method for synthesizing different phases of copper sulphide nanostructures using electrospray deposition (ESD) of molecular sulphur in the form of droplets on metallic copper surfaces under ambient conditions. Different phases of copper sulphide nanostructures were created by controlling the deposition time. Time dependent electron microscopy reveals conversion of the Cu₂S nanopyramids to Cu_1.8S platelets during the course of ESD. In the beginning of deposition, direct interaction between sulphur ions and metallic copper creates Cu₂S nanopyramids followed by subsequent slow diffusion of sulphur leading to the formation of copper deficient Cu_1.8S platelets. A detailed characterization of both the nanostructures was performed by using different microscopic and spectroscopic tools such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS). We have also studied the optical properties of these nanostructures in both UV-Vis and near infrared (NIR) regions. The characteristic broad peaks in the UV-Vis region of Cu₂S nanopyramids indicate the photosensitive nature of the material. A positive photocurrent response was observed from the Cu₂S nanopyramids under electrochemical conditions, while Cu_1.8S nanostructure shows an intense localized surface plasmon (LSPR) peak in the NIR region indicating its metallic nature. Current–voltage (I–V) measurements showed metallic conductivity in them.

Water scarcity is one of the most alarming problems of the planet. An ambient ion based method is developed to make hydrophilic‐hydrophobic patterned silver nanowires (NWs) as humidity harvesters of unprecedented efficiency. Such water harvesters are developed by two‐step surface modification of the as‐synthesized NWs (known from a report earlier) using electrospray. These patterned NWs of ≈20 µm length and ≈200 nm width grown over a relatively large area (2 × 2 cm²) exhibit atmospheric water capture (AWC) efficiency of 56.6 L m⁻² d⁻¹, the highest reported so far. The whole fabrication process of the surface is performed under ambient conditions with a home‐built nanoelectrospray ion source, without the help of any sophisticated instrumentation. The synthesized material combines and mimics two exciting examples of AWC in nature, which are cactae and Namib Desert beetles, which utilize AWC for their living. It is believed that the combination of the special features of the above two natural species helps to achieve the highest water capture efficiency reported till date. A working prototype using this surface for AWC is also fabricated.

Here, we report the synthesis of monolayer protected, luminescent and atomically precise silver sulfide (Ag₂S) clusters. Cluster formation was studied by varying the conditions of the reaction. Matrix assisted laser desorption ionization mass spectrometry (MALDI MS) was used to monitor the growth of clusters to nanoparticles (NPs). Clusters of different nuclearity were obtained at a lower temperature, and were efficiently separated by thin layer chromatography (TLC). One of the clusters was assigned as Ag₁₅₈S₇₉(SBB)₃₂, where SBB is 4-tert-butylbenzyl mercaptan.