Unraveling carrier dynamics and intensity-dependent multi-photon absorption of gold nanorods Sree Satya Bharati Moram, Rajendra Kumar Challa, Rahul Murali, Sampath Kumar Satani, Venugopal Rao Soma, Sai Santosh Kumar Raavi Journal of Physics B Atomic Molecular and Optical Physics, 2025 In this study, we have investigated the hot carrier dynamics and femtosecond (fs) third-order nonlinear optical (NLO) properties of excited plasmonic modes in gold nanorods (Au NRs). Au NRs were synthesized via a seed-mediated growth method, exhibiting an aspect ratio of ∼3.4. The plasmonic local field enhancement of Au NRs was simulated, which undergoes the non-radiative decay to generate hot carriers. The ultrafast dynamics of these generated carriers associated with the longitudinal surface plasmon resonance (LSPR) and transverse surface plasmon resonance (TSPR) bands are investigated using fs transient absorption spectroscopy measurements. The results reveal insight into carrier relaxation after photoexcitation, demonstrating three decay stages: electron–electron scattering in fs, followed by electron–phonon and phonon–phonon interaction in ps, evolving the final energy into the environment. LSPR mode shows higher relaxation times than TSPR mode at three different fluences. Next, the FFT of transient absorption traces revealed that the breathing vibrational frequency of Au NRs decreases with increasing pump fluence. Moreover, the NLO response of these NRs is explored using the fs Z-scan technique at an excitation wavelength of 800 nm at different peak intensities of 17.4–174 GW cm−2. The open-aperture studies revealed a transition in nonlinear absorption behavior from saturable absorption (SA) to reverse SA with increasing incident laser intensity, indicating strong intensity-dependent nonlinear absorption characteristics. The optical limiting threshold of Au NRs was estimated as ∼14 mJ cm−2. The observed NLO response, combined with ultrafast plasmonic dynamics, highlights the potential of this material for applications in nonlinear photonics and optical limiters.
Critical Role of Carrier Cooling Mechanism in WS2/CsPbBr3 Hybrid Nanocomposites for Enhanced Photodetector Performances Sudhanshu Kumar Nayak, Chinmay Barman, Lavadiya Sireesha, Arunkumar Sakthivel, Sree Satya Bharati Moram, Subbiah Alwarappan, Venugopal Rao Soma, Sai Santosh Kumar Raavi Small, 2025 Heterostructures and nanocomposites comprising transition metal dichalcogenides (TMDCs) and halide perovskite nanocrystals (NCs) are prominently used in several optoelectronic devices. Hot carriers (HCs) are the charge carriers possessing higher kinetic energy than surrounded thermal distributions. Properly utilizing these HCs by slowing down their cooling mechanism reduces the energy losses in optoelectronic devices. Herein, employing the femtosecond transient absorption spectroscopy (fs‐TAS) technique, the slowdown processes of HC relaxations are reported in WS2/CsPbBr3 hybrid‐nanocomposites due to the hot‐phonon bottleneck. HCs relaxation time increases from ≈6 ps in CsPbBr3 NCs to ≈10 ps in WS2/CsPbBr3 nanocomposites at an excitation fluence of 17.7 µJ cm−2. The maximum HCs temperature TC increased to 1181 K in WS2/CsPbBr3 nanocomposites with an observed TC of 856 K in pristine NCs. The electron transfer process from NCs to WS2 nanosheets has been observed in these nanocomposites with time component t2 ≈38.0‐102.4 ps in pristine NCs and 20.9–66.9 ps in nanocomposites, became faster at excitation‐fluence of 17.7–99.8 µJ cm−2. Furthermore, a significant enhancement in nanocomposite‐based photodetector confirmed the efficient charge transfer at the heterojunction, resulting ≈400%, ≈420%, and ≈200% increase in the photocurrent, responsivity, and detectivity, respectively, compared to the pristine devices.
Energy-dependent femtosecond LIPSS on germanium and application in explosives sensing Jagannath Rathod, Sree Satya Bharati Moram, Venugopal Rao Soma Journal of Physics D Applied Physics, 2025 In this study, we fabricated laser-induced periodic surface structures (LIPSS) on a germanium surface through laser ablation in air using axicon and femtosecond (fs) pulses. This novel approach permitted the nanoscale material processing outcome refinement via an fs Bessel beam. Our investigations aimed at systematically understanding the formation of periodic structures under various experimental conditions, such as (i) different pulse energies ranging from 50 µJ to 1000 µJ at a constant scan speed and (ii) constant energy with different scan speeds (0.1–3 mm s−1). By adjusting the fluences and scan speeds, we were able to identify the parametric space and alter the periodicity of the low-spatial frequency LIPSS and high-spatial frequency LIPSS on germanium, which were analyzed using field emission scanning electron microscopy. An optimal LIPSS formation over a large area of germanium was achieved at an input energy of 250 µJ and a scan speed of 0.75 mm s−1. Additionally, we measured the contact angles of the Ge nanostructures (GeNSs) to demonstrate their hydrophobic nature and non-wetting properties, providing insights into the behavior of LIPSS. Subsequently, the GeNSs were coated with a ∼15 nm thick gold (Au) film using a thermal deposition method. Utilizing these, the surface-enhanced Raman spectroscopy (SERS) technique detected diverse analytes, such as tetryl (an explosive) at a concentration of 50 µM and thiram (a pesticide) at 500 nM. The SERS enhancement factors for tetryl and thiram molecules on GeNSs coated with a 15 nm-thick Au layer were determined to be 2.5 × 104 and 4.2 × 105, respectively.
Plasmonic nanoparticle sensors: current progress, challenges, and future prospects Krishna Kant, Reshma Beeram, Yi Cao, Paulo S. S. dos Santos, Lara González‐Cabaleiro, et al. Nanoscale Horizons, 2024 Plasmonic nanoparticles (NPs) have played a significant role in the evolution of modern nanoscience and nanotechnology in terms of colloidal synthesis, general understanding of nanocrystal growth mechanisms, and their impact in a wide range of applications. They exhibit strong visible colors due to localized surface plasmon resonance (LSPR) that depends on their size, shape, composition, and the surrounding dielectric environment. Under resonant excitation, the LSPR of plasmonic NPs leads to a strong field enhancement near their surfaces and thus enhances various light-matter interactions. These unique optical properties of plasmonic NPs have been used to design chemical and biological sensors. Over the last few decades, colloidal plasmonic NPs have been greatly exploited in sensing applications through LSPR shifts (colorimetry), surface-enhanced Raman scattering, surface-enhanced fluorescence, and chiroptical activity. Although colloidal plasmonic NPs have emerged at the forefront of nanobiosensors, there are still several important challenges to be addressed for the realization of plasmonic NP-based sensor kits for routine use in daily life. In this comprehensive review, researchers of different disciplines (colloidal and analytical chemistry, biology, physics, and medicine) have joined together to summarize the past, present, and future of plasmonic NP-based sensors in terms of different sensing platforms, understanding of the sensing mechanisms, different chemical and biological analytes, and the expected future technologies. This review is expected to guide the researchers currently working in this field and inspire future generations of scientists to join this compelling research field and its branches.
Effect of wavelength and liquid on formation of Ag, Au, Ag/Au nanoparticles via picosecond laser ablation and SERS-based detection of DMMP Sree Satya Bharati Moram, Chandu Byram, Venugopal Rao Soma Beilstein Journal of Nanotechnology, 2024 The present study investigates the effects of input wavelength (1064, 532, and 355 nm) and surrounding liquid environment (distilled water and aqueous NaCl solution) on the picosecond laser ablation on silver (Ag), gold (Au), and Ag/Au alloy targets. The efficacy of the laser ablation technique was meticulously evaluated by analyzing the ablation rates, surface plasmon resonance peak positions, and particle size distributions of the obtained colloids. The nanoparticles (NPs) were characterized using the techniques of UV–visible absorption, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Furthermore, NPs of various sizes ranging from 6 to 35 nm were loaded onto a filter paper by a simple and effective drop-casting approach to achieve flexible surface-enhanced Raman spectroscopy (SERS) substrates/sensors. These substrates were tested using a simple, portable Raman device to identify various hazardous chemicals (malachite green, methyl salicylate, and thiram). The stability of the substrates was also systematically investigated by determining the decay percentages in the SERS signals over 60 days. The optimized SERS substrate was subsequently employed to detect chemical warfare agent (CWA) simulants such as methyl salicylate (a CWA simulant for sulfur mustard) and dimethyl methyl phosphonate (has some structural similarities to the G-series nerve agents) at different laser excitations (325, 532, and 633 nm). A notably higher SERS efficiency for CWA simulants was observed at a 325 nm Raman excitation. Our findings reveal that a higher ablation yield was observed at IR irradiation than those obtained at the other wavelengths. A size decrease of the NPs was noticed by changing the liquid environment to an electrolyte. These findings have significant implications for developing more efficient and stable SERS substrates for chemical detection applications.
Single-step fabrication of hybrid germanium-gold/silver nanoentities by femtosecond laser ablation and applications in SERS-based sensing Jagannath Rathod, Sree Satya Bharati Moram, Byram Chandu, Paweł Albrycht, Venugopal Rao Soma Nanotechnology, 2023 We present a simple, fast, and single-step approach for fabricating hybrid semiconductor-metal nanoentities through liquid-assisted ultrafast (∼50 fs, 1 kHz, 800 nm) laser ablation. Femtosecond (fs) ablation of Germanium (Ge) substrate was executed in (i) distilled water (ii) silver nitrate (AgNO3—3, 5, 10 mM) (iii) Chloroauric acid (HAuCl4—3, 5, 10 mM), yielding the formation of pure Ge, hybrid Ge-silver (Ag), Ge-gold (Au) nanostructures (NSs) and nanoparticles (NPs). The morphological features and corresponding elemental compositions of Ge, Ge-Ag, and Ge-Au NSs/NPs have been conscientiously studied using different characterization techniques. Most importantly, the deposition of Ag/Au NPs on the Ge substrate and their size variation were thoroughly investigated by changing the precursor concentration. By increasing the precursor concentration (from 3 mM to 10 mM), the deposited Au NPs and Ag NPs’ size on the Ge nanostructured surface was increased from ∼46 nm to ∼100 nm and from ∼43 nm to ∼70 nm, respectively. Subsequently, the as-fabricated hybrid (Ge-Au/Ge-Ag) NSs were effectively utilized to detect diverse hazardous molecules (e.g. picric acid and thiram) via the technique of surface-enhanced Raman scattering (SERS). Our findings revealed that the hybrid SERS substrates achieved at 5 mM precursor concentration of Ag (denoted as Ge-5Ag) and Au (denoted as Ge-5Au) had demonstrated superior sensitivity with the enhancement factors of ∼2.5 × 104, 1.38 × 104 (for PA), and ∼9.7 × 105 and 9.2 × 104 (for thiram), respectively. Interestingly, the Ge-5Ag substrate has exhibited ∼10.5 times higher SERS signals than the Ge-5Au substrate.
Gold nanostars loaded fabrics as flexible, low-cost SERS substrates and swab-based detection of thiram on fruits and vegetables Sampath Kumar Satani, Sree Satya Bharati Moram, Venugopal Rao Soma Journal of Physics D Applied Physics, 2023 Currently, flexible surface-enhanced Raman spectroscopy (SERS) substrates have gained tremendous interest because they enable sample collection from uneven surfaces in real sensing applications. Herein, two different flexible textiles (cotton and synthetic fabrics) loaded with star-shaped gold (Au) nanoparticles (NPs) were utilized for detailed studies and are demonstrated as SERS substrates. Both fabrics were soaked in Au NPs synthesized via a simple wet chemical method. The colloidal star-shaped Au NPs were characterized by UV-visible absorption and transmission electron microscopy techniques. The C- and S-fabrics loaded with Au NPs were characterized by FESEM, x-ray diffraction, and x-ray photoelectron spectroscopic techniques. Subsequently, the SERS efficiency of C- and S-fabrics was examined with thiram, methylene Blue (MB), and Nile Blue (NB) molecules. Furthermore, pesticide (thiram) residues on the surfaces of a banana, an apple, and a spinach leaf were investigated by a simple swabbing method. The utility of these substrates is demonstrated by performing the SERS measurements using a portable Raman spectrometer, which is expedient for real-time applications.
Ultrafast Laser-Ablated Nanoparticles and Nanostructures for Surface-Enhanced Raman Scattering-Based Sensing Applications Sree Satya Bharati Moram, Jagannath Rathod, Dipanjan Banerjee, Venugopal Rao Soma Journal of Visualized Experiments, 2023 The technique of ultrafast laser ablation in liquids has evolved and matured over the past decade, with several impending applications in various fields such as sensing, catalysis, and medicine. The exceptional feature of this technique is the formation of nanoparticles (colloids) and nanostructures (solids) in a single experiment with ultrashort laser pulses. We have been working on this technique for the past few years, investigating its potential using the surface-enhanced Raman scattering (SERS) technique in hazardous materials sensing applications. Ultrafast laser-ablated substrates (solids and colloids) could detect several analyte molecules at the trace levels/mixture form, including dyes, explosives, pesticides, and biomolecules. Here, we present some of the results achieved using the targets of Ag, Au, Ag-Au, and Si. We have optimized the nanostructures (NSs) and nanoparticles (NPs) obtained (in liquids and air) using different pulse durations, wavelengths, energies, pulse shapes, and writing geometries. Thus, various NSs and NPs were tested for their efficiency in sensing numerous analyte molecules using a simple, portable Raman spectrometer. This methodology, once optimized, paves the way for on-field sensing applications. We discuss the protocols in (a) synthesizing the NPs/NSs via laser ablation, (b) characterization of NPs/NSs, and (c) their utilization in the SERS-based sensing studies.
Ag-doped TiO2 Nanoparticles Generated with Femtosecond Laser Ablation for Sensing RDX and Ammonium Nitrate Laser Science Ls 2023 in Proceedings Frontiers in Optics Laser Science 2023 Fio Ls Part of Frontiers in Optics Laser Science 2023, 2023
Ag-doped TiO2 Nanoparticles Generated with Femtosecond Laser Ablation for Sensing RDX and Ammonium Nitrate Laser Applications Conference Lac 2023 in Proceedings Laser Congress 2023 Assl Lac Part of Laser Conference, 2023
Beam Geometry-Controlled Nonequilibrium Formation of WS2/CsPbBr3 Hybrids and Interfacial Carrier Dynamics RK Challa, MSS Bharathi, R Murali, VR Soma, SSK Raavi arXiv preprint arXiv:2603.04990 , 2026 2026
Ag-Cu alloy films as robust substrates for SERS-based sensing applications NM Das, SSB Moram, VR Soma, S Rath, M Gupta, SK Vayalil, G Mattei, ... Vacuum, 115224 , 2026 2026
Functionalized PVP nanofibers achieved using electrospinning as flexible SERS substrates for multiple explosives sensing SK Satani, R Jose, MSS Bharati, V Rao Soma Applied Optics 65 (1), 55-65 , 2025 2025
Unraveling carrier dynamics and intensity-dependent multi-photon absorption of gold nanorods SSB Moram, RK Challa, R Murali, SK Satani, VR Soma, SSK Raavi Journal of Physics B: Atomic, Molecular and Optical Physics 58 (17), 175601 , 2025 2025 Citations: 2
Critical Role of Carrier Cooling Mechanism in WS 2 /CsPbBr 3 Hybrid Nanocomposites for Enhanced Photodetector Performances SK Nayak, C Barman, L Sireesha, A Sakthivel, SSB Moram, ... Small 21 (18), 2410099 , 2025 2025 Citations: 14
Energy–dependent femtosecond LIPSS on germanium and application in explosives sensing J Rathod, SSB Moram, VR Soma Journal of Physics D: Applied Physics 58 (2), 025104 , 2025 2025 Citations: 4
Surface enhanced Raman scattering-based sensing and ultrafast nonlinear optical properties of silver-hexagonal boron nitride nanocomposites achieved by femtosecond laser ablation K Bera, SSB Moram, D Banerjee, J Lahiri, VR Soma Optical Materials 157, 116393 , 2024 2024 Citations: 5
Study on the influence of material properties in femtosecond laser ablation of 6H-SiC in water and SERS-based applications KR Kumar, J Rathod, MSS Bharathi, RSP Goud, S Mahajan, A Sharma, ... Optics Express 32 (21), 37394-37417 , 2024 2024 Citations: 10
Nanostructured bi-metallic Pd–Ag alloy films for surface-enhanced Raman spectroscopy-based sensing application NM Das, A Chauhan, MSS Bharati, K Bera, SS Kumar, VR Soma, ... Journal of Vacuum Science & Technology A 42 (5) , 2024 2024 Citations: 3
Effect of wavelength and liquid on formation of Ag, Au, Ag/Au nanoparticles via picosecond laser ablation and SERS-based detection of DMMP SSB Moram, C Byram, VR Soma Beilstein Journal of Nanotechnology 15 (1), 1054-1069 , 2024 2024 Citations: 4
Plasmonic nanoparticle sensors: current progress, challenges, and future prospects K Kant, R Beeram, Y Cao, PSS Dos Santos, L González-Cabaleiro, ... Nanoscale horizons 9 (12), 2085-2166 , 2024 2024 Citations: 138
Ag-doped TiO2 Nanoparticles Generated with Femtosecond Laser Ablation for Sensing RDX and Ammonium Nitrate D Banerjee, SSB Moram, VR Soma Frontiers in Optics, JM7A. 1 , 2023 2023 Citations: 1
Single-step fabrication of hybrid germanium-gold/silver nanoentities by femtosecond laser ablation and applications in SERS-based sensing J Rathod, SSB Moram, B Chandu, P Albrycht, VR Soma Nanotechnology 34 (40), 405301 , 2023 2023 Citations: 13
Gold nanostars loaded fabrics as flexible, low-cost SERS substrates and swab-based detection of thiram on fruits and vegetables SK Satani, SSB Moram, VR Soma Journal of Physics D: Applied Physics 56 (37), 375103 , 2023 2023 Citations: 11
Author Spotlight: Advancements and Applications in Nanoparticle Synthesis Through Laser Ablation in Liquids SSB Moram, J Rathod, D Banerjee, VR Soma JoVE (Journal of Visualized Experiments), e65450 , 2023 2023
Ultrafast laser-ablated nanoparticles and nanostructures for surface-enhanced Raman scattering-based sensing applications SSB Moram, J Rathod, D Banerjee, VR Soma JoVE (Journal of Visualized Experiments), e65450 , 2023 2023 Citations: 1
Review of ultrafast laser ablation for sensing and photonic applications C Byram, SSB Moram, D Banerjee, R Beeram, J Rathod, VR Soma Journal of Optics 25 (4), 043001 , 2023 2023 Citations: 20
Femtosecond laser patterned silicon embedded with gold nanostars as a hybrid SERS substrate for pesticide detection SSB Moram, C Byram, VR Soma RSC advances 13 (4), 2620-2630 , 2023 2023 Citations: 28
Green machining using graphene-based self-lubricating cutting tool–a preliminary investigation RS Revuru, S Chatti, SSBSS Moram, C Byram, VR Soma World Journal of Engineering 19 (6), 745-754 , 2022 2022 Citations: 2
Plasmonic nanoparticle sensors: current progress, challenges, and future prospects K Kant, R Beeram, Y Cao, PSS Dos Santos, L González-Cabaleiro, ... Nanoscale horizons 9 (12), 2085-2166 , 2024 2024 Citations: 138
Explosives sensing using Ag–Cu alloy nanoparticles synthesized by femtosecond laser ablation and irradiation MSS Bharati, B Chandu, SV Rao RSC advances 9 (3), 1517-1525 , 2019 2019 Citations: 113
Instantaneous trace detection of nitro-explosives and mixtures with nanotextured silicon decorated with Ag–Au alloy nanoparticles using the SERS technique SSB Moram, AK Shaik, C Byram, S Hamad, VR Soma Analytica Chimica Acta 1101, 157-168 , 2020 2020 Citations: 93
Femtosecond laser fabricated Ag@ Au and Cu@ Au alloy nanoparticles for surface enhanced Raman spectroscopy based trace explosives detection M Sree Satya Bharati, C Byram, VR Soma Frontiers in Physics 6, 28 , 2018 2018 Citations: 90
SERS based detection of multiple analytes from dye/explosive mixtures using picosecond laser fabricated gold nanoparticles and nanostructures C Byram, SSB Moram, VR Soma Analyst 144 (7), 2327-2336 , 2019 2019 Citations: 85
Ultra-sensitive reusable SERS sensor for multiple hazardous materials detection on single platform TK Naqvi, A Bajpai, MSS Bharati, MM Kulkarni, AM Siddiqui, VR Soma, ... Journal of hazardous materials 407, 124353 , 2021 2021 Citations: 79
Femtosecond laser-induced, nanoparticle-embedded periodic surface structures on crystalline silicon for reproducible and multi-utility SERS platforms S Hamad, SS Bharati Moram, B Yendeti, GK Podagatlapalli, ... Acs Omega 3 (12), 18420-18432 , 2018 2018 Citations: 73
Versatile gold based SERS substrates fabricated by ultrafast laser ablation for sensing picric acid and ammonium nitrate C Byram, SSB Moram, AK Shaik, VR Soma Chemical Physics Letters 685, 103-107 , 2017 2017 Citations: 71
Plasmon-enhanced ultrafast and tunable thermo-optic nonlinear optical properties of femtosecond laser ablated TiO2 and Silver-doped TiO2 nanoparticles D Banerjee, SSB Moram, C Byram, J Rathod, T Jena, GK Podagatlapalli, ... Applied Surface Science 569, 151070 , 2021 2021 Citations: 61
Femtosecond, broadband nonlinear optical studies of a zinc porphyrin and zinc phthalocyanine MSS Bharati, S Bhattacharya, JVS Krishna, L Giribabu, SV Rao Optics & Laser Technology 108, 418-425 , 2018 2018 Citations: 60
Enhanced catalytic and SERS performance of shape/size controlled anisotropic gold nanostructures K Nehra, SK Pandian, MSS Bharati, VR Soma New Journal of Chemistry 43 (9), 3835-3847 , 2019 2019 Citations: 52
Hierarchical laser-patterned silver/graphene oxide hybrid SERS sensor for explosive detection TK Naqvi, M Sree Satya Bharati, AK Srivastava, MM Kulkarni, AM Siddiqui, ... ACS omega 4 (18), 17691-17701 , 2019 2019 Citations: 51
Gold-nanoparticle-and nanostar-loaded paper-based SERS substrates for sensing nanogram-level Picric acid with a portable Raman spectrometer SSB Moram, C Byram, VR Soma Bulletin of Materials Science 43 (1), 53 , 2020 2020 Citations: 50
Structural, optical and femtosecond third-order nonlinear optical properties of LiNbO3 thin films A Tumuluri, MSS Bharati, SV Rao, KCJ Raju Materials Research Bulletin 94, 342-351 , 2017 2017 Citations: 46
Quantitative analysis of catalysis and SERS performance in hollow and star-shaped Au nanostructures K Nehra, SK Pandian, C Byram, SSB Moram, VR Soma The Journal of Physical Chemistry C 123 (26), 16210-16222 , 2019 2019 Citations: 45
Synthesis and femtosecond third order nonlinear optical properties of push-pull trans-A2B-corroles P Yadav, T Anand, SSB Moram, S Bhattacharya, M Sankar, SV Rao Dyes and Pigments 143, 324-330 , 2017 2017 Citations: 40
Large area few-layer hexagonal boron nitride as a Raman enhancement material N Basu, MS Satya Bharathi, M Sharma, K Yadav, AS Parmar, VR Soma, ... Nanomaterials 11 (3), 622 , 2021 2021 Citations: 39
Fabrication of nanocages on nickel using femtosecond laser ablation and trace level detection of malachite green and Nile blue dyes using surface enhanced Raman spectroscopic … B Chandu, MSS Bharati, P Albrycht, SV Rao Optics & Laser Technology 131, 106454 , 2020 2020 Citations: 38
