lanthanum oxyfluoride nanostructures prepared by modified sonochemical method and their use in the fields of optoelectronics and biotechnology

Therefore, use of stable synthesized LaOF: Dy3+ in powder dusting method creates a significant interest for scientific community to visualize the LFPs as a labeling agents.. The present

Lanthanum oxyfluoride nanostructures prepared by modified sonochemical

method and their use in the fields of optoelectronics and biotechnology

C Suresh, H Nagabhushana, G.P Darshan, R.B Basavaraj, B Daruka Prasad,

S.C Sharma, M.K Sateesh, J.P Shabaaz Begum

DOI: http://dx.doi.org/10.1016/j.arabjc.2017.03.006

Please cite this article as: C Suresh, H Nagabhushana, G.P Darshan, R.B Basavaraj, B Daruka Prasad, S.C Sharma, M.K Sateesh, J.P Shabaaz Begum, Lanthanum oxyfluoride nanostructures prepared by modified

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biotechnology

C Suresh 1, 2 , H Nagabhushana 1* , G P Darshan 3 , R B Basavaraj 1 , B Daruka Prasad 4 ,

S.C Sharma 5 , M.K Sateesh 6 , J.P Shabaaz Begum 6

Department of Physics, B M S Institute of Technology and Management, Affiliated to VTU,

Belagavi, Bangalore 560 064, India

5

Department of Mechanical Engineering Jain University, Advisor, Jain group of Institutions,

Bangalore 560069, India

6

Molecular diagnostics and Nanotechnology laboratories, Department of Microbiology and

Biotechnology, Bangalore University, Bangalore -560 056, India

* Corresponding author: +91- 9663177440, E-mail: bhushanvlc@gmail.com (H Nagabhushana)

Abstract

Dysprosium doped lanthanum oxyfluoride nanostructures were prepared by modified

sonochemical method using Aloe Vera gel as a bio-surfactant The morphology of the product

was systematically studied by varying different experimental parameters including concentration of surfactant, sonication time, pH and sonication power It was found that some

of these above parameters play a key role in tuning the morphology of the product The photoluminescence studies exhibited characteristic emission peaks at ~ 483 nm, 574 nm and

674 nm attributed to 4F9/2→6

H15/2, 4F9/2→6

H13/2 and 4F9/2→6

H11/2 transitions of Dy3+ ions respectively The optimal concentration of Dy3+ ions was found to be ~ 3 mol % The photometric studies revealed that the prepared samples were quite useful for the fabrication

of white light emitting diodes The optimized product was also tested for their capability as

an antigen against the bacterial and fungal pathogens The present method of preparation may

be scaled up easily to the larger production for industrial applications The optimized sample showed an effective visualization of latent fingerprints on various forensic relevant materials

Keywords: Sonochemical method; Photoluminescence; Latent fingerprint; antimicrobial;

antifungal

conventional incandescent or fluorescent lamps due to its long life time, high brightness, eco- friendly and high efficiency characteristics (Lin et al., 2011; Park et al., 2003; Im et al., 2009) The phosphors converted WLEDs (pc-WLEDs) consists of near ultraviolet chips which finds wide range of applications due to excellent color stability and reproducibility (Chen et al., 2012; Zhang et al., 2013) Commercially available pc-WLEDs constitutes of InGaN chip with Y3Al5O12:Ce3+ (YAG: Ce) phosphor suffers from low color rendering index and high correlated color temperature (CCT) due to the lack of red component in it (Hecht et al., 2009; Jung et al., 2006) Hence, rare earth doped particularly lanthanide-doped luminescent materials are considered to be an ideal hosts for better luminescence properties due to their high refractive index and low phonon energy Further, these materials created new avenues for researches due to their possible applications in various biomedical fields such as biological labels, biosensors, multimodal bio-imaging, photodynamic therapy and drug delivery etc (Ruirui Xing., 2016a; Ruiyun Zhang., 2016; Ruirui Xing., 2016b; Ruirui Xing., 2016c) Ruirui Xing synthesized functional hybrid multilayer films of collagen-capped gold nanoparticles by layer-by-layer assembly technique Prepared samples showed efficient regulating cell growth and detachments (Ruirui Xing., 2016d)

So far, various synthesis routes were used including solution combustion, sol – gel, co- precipitation, solid state reaction, hydrothermal methods etc (Hu et al., 1999; Xia et al., 2009; Gai et al., 2014; Tana et al., 2011; Kaczmarek et al., 2013) Morphologies of the compounds not only control their properties but also enhance the effectiveness for the various applications (Alivisatos, 1996) However, in some of these routes it is difficult to control over the morphology, size and stoichiometric compositions Therefore, a lot of research has been needed for the improvement of versatile synthesis routes Ultrasound assisted

irradiation provides remarkable reaction conditions to initiate the chemical reaction (Suslick, 1990) The impact of the ultrasound force to acoustic cavitation leads to the formation, growth and implosive collapse of bubbles of the reaction mixture leads to superstructures (Suslick, 1996)

Generally fingerprints (FPs) encompasses a mixture of substances originating from the sweat glands namely epidermis, secretory glands in the dermis along with intrinsic components including drugs, medication traces, metabolites and extrinsic contaminants namely blood, food contaminants, dirt and grease, hair and moistures (Darshan et al., 2016a) The ridge arrangement of the skin on human finger create a distinctive FP By touching an object, sweat emitted through the pores in the skin can be moved to the surface to leave an impression of the ridge pattern Such invisible prints were recognized as a Latent finger prints (LFPs) which are useful for the recognition and detection of individuals at forensic science

For the past few decades, various visualization methods were established to enhance LFPs Nevertheless, there still exist a lack of sensitivity and selectivity (Saif, 2013) Presently nanoparticles were utilized in forensic investigations due to small crystalline size, flexibility and ability to precisely tune their surface properties The surface modification versatility of these materials may lead to accurate targeting and to increase selectivity (Cadd

et al., 2015)

Powder dusting was simple and most frequently used method for revealing the LFPs (Champod et al., 2004) in which powder of bronze, ferric oxide and rosin were used These powders were unable to reveal LFPs on some relevant forensic surfaces as it was hazardous and uneven crystallite size Alternatively, use of powder-based luminescent nanophosphors was the best solution to conquer such limitations Rare earth doped nanophosphors have been

extensively investigated as a potential labeling agents to visualize LFPs with high contrast, good sensitivity and reduced background hindrance due to smaller crystallite size and better adhesion efficiency (Darshan et al., 2016 b) Furthermore, it was well established that the lanthanide ions were bio-compatible with low toxicity Therefore, use of stable synthesized LaOF: Dy3+ in powder dusting method creates a significant interest for scientific community

to visualize the LFPs as a labeling agents

The present work describes the synthesis of LaOF: Dy3+ (1-11 mol %) nanostructures

(NS) by facile ultrasound assisted sonochemical route using A.V gel as bio-surfactant The

effectiveness and unique properties of ultrasound for the fabrication of nanostructured materials was successfully explored Further, to evaluate the potential applications of the prepared samples, the photoluminescence (PL) and photometric properties (CIE and CCT) were studied in detail The optimized sample was used as a labeling agent for the visualization of LFPs on various forensic relevant surfaces

2 Experimental 2.1 Synthesis

The precursors used for the preparation of LaOF NS were of analytical grade without further purification The chemicals used were lanthanum nitrate [La (NO3)3.4H2O (Sigma Aldrich; 99.9 %)], ammonium fluoride [NH4F; (Sigma Aldrich; 99.9 %)] and dysprosium nitrate [Dy (NO3)3; (Sigma Aldrich; 99.9 %)] A.V gel was used as a bio-surfactant and the detailed

preparation procedure for obtaining A.V gel from aloe vera plant was reported elsewhere

(Kavyashree et al., 2015) Stoichiometric quantities of the precursors and 50 ml of A.V gel

(bio-surfactant) and 150 ml of double distilled water were dissolved and mixed using magnetic stirrer for ~ 25 min to get a clear solution Resulting mixture was divided into various wt% from 5% to 30% W/V and subjected to sonochemical treatment with the help of Mrc Laboratory equipment model-AC 120H, probe, ultrasonic frequency of ~ 20 kHz, power

of ~ 300 W and sonication time ~ 1 - 6 h at a fixed temperature of 80 C NaOH was used as

a precipitating agent and used to adjust pH value The precipitate obtained at the end of the reaction was filtered several times using double distilled water and alcohol The powder was dried at 80 C for 3 h in a hot air oven and then heat treated at ~ 700 oC for 3 h The schematic illustration for the ultrasound assisted sonochemical synthesis was shown in Fig.1

2.2 Characterization

Phase purity and structural analysis of the product was done by using Shimadzu made powder X-ray diffractometer (PXRD) Morphology was examined by Hitachi scanning electron microscopy (SEM) Particle size was determined by Hitachi (H-8100) made transmission electron microscope (TEM) equipped with EDAX The Fourier transform infrared (FTIR) studies were done by Perkin Elmer Spectrometer (Spectrum 1000) The DRS of the samples was recorded on Lambda-35, Perkin Elmer spectrophotometer Jobin Yvon

Spectroflourimeter Fluorolog-3 was used for photoluminescence (PL) studies

2.3 Visualization of LFPs by using LaOF: Dy 3+ (3 mol %) NS

The fresh FPs were deposited on various surfaces including glass, CD, mobile screen, marble, computer mouse and pet bottle Before deposition, the standard procedure was followed to get the finger prints as reported elsewhere (Darshan, G.P et al., 2016) The optimized (3 mol

%) NS were smoothly applied on the LFPs by powder dusting method and excess powder was removed by smooth brushing A Nikon D3100/ AF-S Nikkor 50 mm f/1.8G ED lens digital camera and a 254 nm UV light was used for the visualization of FPs The schematic representation for the revelation of LFPs was shown in Fig.2

2.4 Evaluation of bactericidal activity of LaOF: Dy 3+ nanostructures against Test micro organisms

Test Microorganisms and reference strain

Four American Type Culture Collection (ATCC) (Table 1), registered bacterial isolates were

used for bactericidal activity of A.V gel mediated LaOF: Dy3+ NS All the glassware’s were sterilized by autoclaving at 121 °C for 15 m before using in the assay In the present investigation, four bacteria were cultured on Mueller-Hinton agar (Hi-Media, Mumbai, India) and plates were incubated for 24 h in aerobic conditions at 37 °C A single colony from the stock bacterial culture was used for preparing the bacterial suspensions 20 ml of sterile Mueller-Hinton broth and 100 ml Erlenmeyer flask were inoculated and these were kept in a shaker at 200 rpm for 24 ± 2 h and again incubated at ~ 37 °C Further, an optical density of McFarland of 0.5 (1 × 108 CFU/mL) with bacterial suspension was made separately with isotonic solution of NaCl (0.85%) Later, the bacterial suspension was diluted ten times (1 × 107 CFU/mL) and used as inoculum in testing for bactericidal activity

2.5 Determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) by Micro broth dilution method

The MIC was determined by employing Clinical and Laboratory Standards with some slight modifications using 96 well micro broth dilution plate and bacterial strains concentration

A stock suspension was obtained by suspending the prepared of LaOF: Dy3+ NS in milli-Q water to meet a final concentration 100 µg/mL (Balouiri et al., 2016) Then the aliquot was mixed with Mueller-Hinton broth for subsequent experiments Further, bacterial strains were exposed to LaOF: Dy3+ (3 mol %) NS ranging from 25 to 0.000025 μg/mL in ten-fold dilution series The similar procedure was employed for determination of MIC for both positive (tetracycline-25 μg/mL) and negative (sterile Mueller-Hinton broth without NS) controls 20 μL of the bacterial suspension was added to each microtitre well and incubated at

37 °C for 24 h To obtain better results, all the experiments were repeated in triplicates

Afterward, MIC values of the NS were revealed by adding 25 μL of iodonitrotetrazolium

chloride (INT at 0.5 mg/mL) in each well after 24 h The microtitre plates were additionally incubated at 37 °C for 60 m MICs of test compounds were resolved for the lowest concentration of NS or drug that restricted the color change from colorless to red MBC determined by subculting of 50 μL cultured suspension (without INT) by streaking on Mueller-Hinton (MH) agar in petriplate and later incubated for 24 h at 37 °C MBC was the lowest concentration that completely stops the bacterial growth on MH agar surface

2.6 Evaluation of Antifungal Activity of LaOF: Dy 3+ (3 mol %) NS

F oxysporum, phytopathogenic fungi of tomato blight was procured from the culture

collection at Centre of the Molecular Diagnostics Laboratory, Department of Microbiology

and Biotechnology, Bangalore University, Bangalore, India The F oxysporum was grown on

SDA at 25 ± 10 °C and incubated with alternative cycle of 12 h (dark and light) Evaluation of antifungal activity was performed by the food poison technique with slight modifications

The sterilized SDA media was amended with synthesized NS of different concentrations (100 μg/mL, 300 μg/mL, 500 μg/mL, 700 μg/mL and 900 μg/mL) The medium without NS

(control) were decanted into the petri dishes The mycelial agar disc (5 mm) was bored aseptically with the help of sterile cork-borer for 7 days Such mycelial agar was inoculated

to each petri dish containing different concentrations of synthesized NS and control media (without NS) All the Petri dishes were incubated for 7 days at 25 ± 3 °C The antifungal activity of LaOF: Dy3+ NS on F oxysporum was determined by measuring the radial growth

(in cm) Further, antifungal activities of NS were compared with traditional fungicide bavistin (carbendazim) The antifungal effect of nanoparticles was determined as mentioned below

100dc

dt-dcgrowth

oxysporumF

ofinhibition

- (1)

where dc ; the average increase in F oxysporum growth (control) and dt ; the average increase in F oxysporum growth (tested samples)

2.7 Statistical Analysis

The antifungal experimental data was analyzed by mean ± SE subjected to multivariate analysis Further, the mean ± SE separated by Duncan’s multiple range test at 0.5 significance (P < 0.05) using SPSS software (version 19)

3 Results and discussion

PXRD profiles of pure and Dy3+ (1-11 mol %) doped LaOF NS was shown in Fig.3 (a)

All the patterns exhibit sharp and broad diffraction peaks and well matched with the standard JCPDS card No.89-5168 (Dhananjaya et al., 2016) Further, no impurity peaks were observed with increase of Dy3+ concentration indicating that the product was pure The broad diffraction peaks in the present studies was normally associated with crystallite size or strain present in the prepared sample Debye – Scherrer’s relation was utilized to determine the average crystallite sizes as reported elsewhere (Venkataravanappa et al., 2016a) In order to compare the crystallite sizes as well as strain present in the sample W – H plots were utilized and the obtained plots is given in Fig.3 (b) (Venkataravanappa et al., 2017b) Further, the estimated average crystallite size as well as the lattice strains were given in Table 2 As can

be evident from the table the lattice strain was found to be increase with Dy3+ concentration due to lattice distortion (Nagabhushana et al., 2016)

Rietveld refinement method was used to evaluate the various structural parameters namely Pseudo-Voigt profile function (u, v and w), isothermal temperature factors (Biso), backgrounds scale factor, atomic coordinates etc (Daruka Prasad et al., 2014) The observed, calculated and the difference PXRD profiles of LaOF: Dy3+ (3 mol %) was shown in Fig 3 (c) The experimental and calculated profiles showed nearly to zero in the intensity scale as illustrated by a line (Yobs–Ycalc) The refined structural parameters for LaOF: Dy3+ (1- 11 mol

%) NS was summarized in Table 3 It was noticed that a slight variation in structural

R R

- (2)

where Rm and Rd; radii of host material and dopant ion respectively The estimated value of

Dr was found to be ~ 25 % Further it was clear that the dopant Dy3+ substituted into La3+ ions

in LaOF host lattice From the Diamond software, packing diagram was simulated by using

the refined lattice parameters as well as atomic positions and shown in Fig.3 (d) It was evident that La3+/ Dy3+ ions were co-ordinate by four oxide and four fluoride anions as well

as occupy the six-fold 6cWyckoff positions and the symmetry for La3+ ions was C3v(Dhananjaya et al., 2016)

Fig.4 shows the SEM micrographs of LaOF: Dy3+ (3 mol %) NS prepared at different

sonication times (1 – 6 h) with 30 ml of A.V gel and pH = 5 When the sonication time was

~1 h, all the structures appear to be almost spherical in shape and form a network structure (Fig.4 (a & b)) When the sonication time was increased to 2 h, it forms a spherical shaped network structure derive together to form a layer like structure consist of several hollow pores

(Fig 4 (c & d)) Further, when the sonication time was increased to 3 and 4 h, pores were

found to be reduced (Fig.4 (e, f)) Finally, when the sonication time was further increased to 5 and 6 h, these hollow pores were almost reduced (Fig.4 (g, h)) The effect of concentration of

bio - surfactant (A.V gel) on the morphology of the prepared samples was also studied and

was shown in Fig.5 Initially, when the A.V gel concentration was ~ 5 ml small plate like

structures were observed (Fig.5 (a)) When the concentration of A.V gel was increased to 10

and 15 ml, the plate like structures were oriented in multi directions (Fig.5 (b & c)) Further

when the A.V gel concentration increased to 20 and 30 ml, plate like structures were

undergoing self – assembly in a particular direction (Fig.5 (d & e)) Table 4 shows the list of

major phytochemicals extracted in A V gel confirmed from Gas Chromatography Mass

Spectroscopy (GCMS) Fig.6 shows the egg box model for the trapping of LaOF: Dy3+ NS in

the network of Guanosine content of the A.V gel

Fig.7 shows the SEM micrographs of LaOF: Dy3+ (3 mol %) NS synthesized with

different pH values (1 – 11) in presence of A.V gel (30 ml) and 3 h ultrasound irradiation At

lower pH values (1 and 5) agglomerated flake like structures were obtained (Fig 7(a & b))

As the pH value was further increased to 9 and 11, agglomerated flakes ripened to form a dumbbell shaped network structures (Fig 7 (c & d)) The effect of sonication power on the morphology of the prepared samples were also studied and shown in the Fig.8 From the figure, it was clear that when the sonication power was 20 and 24 kHz, an uneven shaped structures with numerous pores were observed (Fig.8 (a & b)) However, with increase of sonication power to 26 & 30 kHz, the agglomeration in the structures was slightly reduced (Fig.8 (c & d)) To know the effect of ultrasound irradiation on morphology, normal mechanical stirring was applied for different time intervals (3 & 6 h) The obtained SEM morphology of LaOF: Dy3+ (3 mol %) were shown in Fig.9 It was evident from the SEM micrographs, no definite shape and size of the particles were observed The aforementioned

results evident that, sonication irradiation time, concentration of A.V gel, pH and sonication

power play a vital role in tuning the morphology of the product

The TEM images of LaOF: Dy3+ (3 mol %) NS was shown Fig.10 (a) It was observed that particles were almost dumbbell in shape which was well matched to those obtained from SEM results The interplanar spacing (d) was estimated from HRTEM and found to be ~ 0.28

nm (Fig 10 (b & c)) Further, the product shown to be highly crystalline in nature as can be evident from SAED patterns (Fig 10(d)) The elements present in the products were confirmed from EDAX results (Fig 10(e))

F9/2+6H7/2 for the Dy3+ ions (Munirathnam et al., 2016; Neharika et al., 2016) The bands at ~

794, 899 and 1071 were due to 4f - 4f transitions of Dy3+ ions The peaks at 275 nm and 313

nm were due to the 8S7/26

J and 6PJ8

S7/2 transitions of La3+ ions (Escobedo Morales et al., 2007) The direct energy band gap (Eg) of the synthesized LaOF: Dy3+ (1-11 mol %) NS were estimated by the Kubelka-Munk (K-M) theory The K - M function F (R∞) and photon energy (h) was estimated by relations reported elsewhere (Som et al., 2014) The value of Eg was estimated by plotting a graph of F(R)2 versus h and extrapolating the linear fitted regions to F(R)2=0 (Fig 11(b)) The obtained values were tabulated and presented in Table 2 As can be

seen from the table, a small variation in Eg values was due to the disorder in the host as well

as defects caused during synthesis (Ravikumar et al., 2014)

Fig.12 shows the FTIR spectra of LaOF: Dy3+ (1-11 mol %) NS were recorded in the range 300–4000 cm-1 The spectra exhibit two characteristic absorption bands at ~ 500 and

370 cm-1 were attributed to La–O vibrations (Dhananjaya, N et al., 2016) The weak absorption band observed at ~1540 cm-1 was due to the adsorption of CO32- from the surrounding atmosphere The peak obtained at ~ 3690 cm-1 was attributed to the bending vibration of surface adsorbed water molecule

Fig.13 (a) shows the PL excitation spectrum of LaOF: Dy3+ (3 mol %) NS monitored

at 574 nm emission The excitation spectrum consists of three important regions i.e., f - f

transition, charge transfer transition and band to band absorption The first part of the spectra consist of peaks centered at ~ 324, 350, 366, 386, 425 and 448 nm were attributed to

of charge transfer band (CTB) was estimated by Jorgensen relation (Darshan et al., 2016d)

By utilizing the values of opt X = 1.1 and  3 +

Dy

opt

 = 1.22, the location of O2Dy3+

CTB can be estimated and found to be ~ 277 nm The asymmetric peak at ~ 315 nm was related to absorption band in the host LaOF matrix

Fig.13 (b) shows the emission spectra of LaOF: Dy3+ (1-11 mol %) NS was recorded upon excited at 354 nm at room temperature (RT) The spectra exhibit a sharp and intense peaks at blue (483 nm; 4F9/2→6

H15/2), yellow (574 nm; 4F9/2→6

H13/2) and red (674 nm; 4

F9/2→6

H11/2) (Amith Yadav et al., 2017; Devaraja et al., 2014) From the figure, it was clear that yellow region was more prominent when compared to other two regions The most intense peak at ~ 574 and ~ 483 nm corresponds to electric dipole and magnetic dipoles of the

Dy3+ ions respectively The effect of Dy3+ ions on the PL emission intensity was studied and

shown in Fig.13 (c) It was noticed that PL intensity increases up to 3 mol % and afterwards it

starts diminishes due to concentration quenching (Blasse, 1986) Further, the asymmetric ratio (A21) was estimated using the relation (Dhanalakshmi et al., 2017);

d I

A

2 / 15 6 2 / 9 4 1

13/2 6 9/2 4 2 21

HF

- (3)

where I1 and I2; intensity at 483 and 574 nm respectively It was found that A21 increases up

to 3 mol % and thereafter it decreases with increase of Dy3+ concentration (Fig.13 (c)) The

distance between Dy3+ activator ions reduces at higher concentration, which hints to the radiative energy transfer between Dy3+ ions The critical distance (Rc) was assessed using the relation (Blasse, 1994):

3 / 1

4 3

~ 5.985 which was near to 6 From this result one can conclude that the charge transfer

mechanism was due to d-d interaction

Fig.16 (a) shows the Commission Internationale de I’Eclairage (CIE), 1931 chromaticity diagram (Publication CIE no 17.4 Colorimetry, 1987; Publication CIE no 15.2 Colorimetry, 1986) of LaOF: Dy3+ NS under 384 nm excitation and the corresponding color

coordinate values were given in Table 5 From the diagram, it was apparent that all of the

CIE values of LaOF: Dy3+ NS were well located in white light region Further, it was noticed that the white light color of the NS was tuned by changing the Dy3+ concentrations Correlated Color Temperature CCT was calculated by transforming the (x, y) co-ordinates of the light source to (U0, V0) by following relations:

3122

x

U - (6)

3122

where n = (x − x e )∕(y − y e) ; the inverse slope the line, (x, y) ; the chromaticity co-ordinates

and x e = 0.3320, y e = 0.1858 ; the epicenter with which the CCT value was obtained in the

range ~ 4341 - 5802 K The corresponding CCT values for different Dy3+ concentration was listed in Table 5 Generally, when CCT value was less than 5000 K indicates the warm white light source used for home appliances (Som et al., 2012) Hence, the studied phosphor was highly suitable for ideal white light emission for home appliances

Generally, the visualization of LFPs on various surfaces was practically challenged for forensic investigators due to absorption of the constituents of LFPs by these materials To evaluate the versatility of the prepared sample, LFPs were visualized on different surfaces namely glass, marble, computer mouse, CD, mobile screen, PET bottle (Fig.17) Interestingly, a minutiae ridge patterns such as core, termination, bifurcation, hook, island and bridge were visualized on all surfaces without any background interference

Fig.18 shows the post processed fingerprint image on glass surface visualized by using optimized LaOF: Dy3+ (3 mol %) NS From the figure, it was evident that the synthesized product was noticeably enhanced level 2 minutiae ridge patterns effortlessly due

to their smaller crystallite size The magnified images of various permanent minutiae were also shown in Fig.18 The level 3 patterns (sweat pores) were innovative details for

authentication of individuals in forensic analysis where partial fingerprints or lack of explicit level 2 details From the Fig.18, it was clear that in addition to level 2 patterns, level 3 substructures (sweat pores) from which the sweat can be secreted, could also be enhanced Fig 19 shows the different fingerprint patterns (loop and whorl) were visualized on glass surface It was evident that, the images were clear and useful for identification of individuals

In the present work, we successfully explored novel LaOF: Dy3+ (3 mol %) NS as a labeling agent to visualize LFPs on different surfaces The visualized LFPs exhibit high efficiency (because procedure involves simple setup and rapid and performed less than 5 min) and high sensitivity (because no color hindrance and chemical constituents can be observed due to smaller crystalline size)

The tested pathogenic microorganisms were accountable for plentiful diseases, cases

of hospital infection, colonization of medical devices, and also testified for the abilit y to acquire resistance (Chen et al., 2015) The MIC and MBC values of synthesized LaOF: Dy3+

(3 mol %) NS with different concentration of A.V gel against bacteria were listed in Table 6

In Gram-negative bacteria, NS synthesized with 1% of A.V gel showed a MIC at 0.25 μg/mL for E coli and 0.025 μg/mL for K pneumoniae and P aerugeinosa However, the MICs was

observed for Gram-positive bacteria (S aureus) with 0.25 μg/mL (Fig 20) The bactericidal

activity of NS was decreased with the increase of concentration of A.V gel (Table 6) In MBC test, 0.25 μg/mL was high enough to destroy K pneumonia and P aeruginosa Whereas, in S aureus and E coli showed similar effect at 2.5 μg/ mL However, NS prepared with 11 % of A.V gel was showed MBC of 25 μg/mL for S aureus, E coli, K pneumonia and P aeruginosa (Table 6)

The percentage inhibition of F oxysporum in terms of colony growth diameters were

studied after 7 days of incubation with optimized LaOF: Dy3+ (3 mol %) NS was shown in Table 7 The percentage inhibition was enhanced from 12.10 to 93.92 with increase of LaOF:

Dy3+ (3 mol %) concentration (100 to 700 μg/mL) (Fig.21) As can be evident from the table,

significant variations were observed with different concentrations of LaOF: Dy3+ (3 mol %)

NS Further, 700 μg/mL of NS were effectively inhibit the growth of F oxysporum (Fig.21) The variation of percentage inhibition (F oxysporum) with different concentration (100 - 700

μg/mL) of LaOF: Dy3+

(3 mol %) NS were shown in Fig.22

From the above results, it was clear that NS derived fungicides can be achieved in a simple cost-effective manner and appropriate to articulate the new categories of nano-biotic components To the best of our knowledge, this was the first report on antimicrobial studies

of lanthanum oxyfluoride NS Therefore, lanthanum oxyfluoride NS can offer future applications as antimicrobial drug in medicine, agriculture and water purification technology

4 Conclusions

For the first time, white light emitting LaOF: Dy3+ (1– 11mol %) NS were prepared by

ultrasound assisted sonochemical method using A.V gel as bio-surfactant Various

experimental parameters were used to study the morphology of the product TEM results indicate that the particles were in nano size lies between 25–35 nm From DR spectra, direct energy gap (Eg) values were estimated and found to be in the range ~ 4.13 - 4.53 eV The emission peaks at ~ 324, 350, 366, 386, 425 and 448 nm were attributed to 6H15/2→4M17/2, 6

Acknowledgement

The author Dr H Nagabhushana thanks to VGST, Karnataka for the sanction of this Project

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Figure.4 SEM images of LaOF: Dy3+ (3 mol %) NS synthesized with different sonication

times (a, b) 1 h, (c, d) 2 h, (e) 3 h, (f) 4 h, (g) 5 h and (h) 6 h with A.V gel (30 ml) and

pH = 5 Figure.5.SEM images of LaOF: Dy3+ (3 mol %) NS synthesized with different concentrations

of A.V gel (a) 5 ml, (b) 10 ml, (c) 15 ml, (d) 20 ml, and (e) 30 ml with 3 h ultrasonic

irradiation time and pH = 5

Figure.6.The egg box model of LaOF: Dy3+ NS with Guanosine content of A.V gel

Figure.7.SEM images of LaOF: Dy3+ (3 mol %) NS synthesized with various pH values (1, 5,

9 and 11) in presence of A.V gel (30 ml) and 3 h ultrasound irradiation

Figure.8.SEM images of LaOF: Dy3+ (3 mol %) NS synthesized with different sonication

power (20, 24, 26 and 30 kHz) in presence of A.V gel (30 ml) and 3 h ultrasound

irradiation

Figure.9.SEM images of LaOF: Dy3+ (3 mol %) NS synthesized with normal mechanical stirring at (a) 3 h and (b) 6 h

Figure.10 (a) TEM (b) HRTEM (c) enlarged portion of HRTEM (d) SAED pattern and (e)

EDAX of LaOF: Dy3+ (3 mol %) NS

Figure.11 (a) DR spectra and (b) Eg plots of LaOF: Dy3+ (1–11 mol %) NS

Figure.12 FTIR spectra of LaOF: Dy3+ (1-11 mol %) NS

Figure.13 (a) Excitation spectrum (b) Emission spectra (c) Variation of PL intensity and

asymmetric ratio with Dy3+ concentration and (d) Energy level diagram of Dy3+ ions Figure.14 Schematic representation of concentration quenching phenomena in Dy3+ ions.Figure.15 Logarithmic plot of x and (I/x) in LaOF: Dy3+ (1–11 mol %) NS

Figure.16 (a) CIE and (b) CCT diagram of LaOF: Dy3+ (1-11 mol %) NS

Figure.17 Finger print images visualized by using LaOF: Dy3+ (3 mol %) NS on (a) glass (b)

marble (c) computer mouse (d) CD (e) mobile screen and (f) PET bottle

Figure.18 High-resolution fluorescence image of finger print The magnified images shows

minutiae ridge patterns (1) core, (2) termination, (3) bifurcation, (4) island, (5) bridge, (6) Hook and (7) sweat pores

Figure.19 Fingerprint images visualized by LaOF: Dy3+ (3 mol %) NS display (a) loop and

(b) Whorl

Figure.20 Antibacterial activity of LaOF: Dy3+ (3 mol %) NS synthesized using different

concentrations A.V gel (A-1 %, B-3 %, C-5 %, D-7 %, E-9 %, F-11 %) on effects

bacterial & fungal pathogens

Figure.21 Antifungal effect of LaOF: Dy3+ (3 mol %) NS on Fusarium oxysporum

(Concentration in µg/ml)

Table 2: Estimated crystallite size, micro strain, lattice strain, dislocation density, stacking

fault and energy gap (Eg) values of LaOF: Dy3+ (1-11 mol %) NS

Table 3: Rietveld refinement parameters of LaOF: Dy3+ (1- 11 mol %) NS

Table 4: List of major phytochemicals extracted in A V gel confirmed from GCMS

Table 5: Photometric parameters of LaOF: Dy3+ (1-11 mol %) NS

Table 6: Evaluation of bactericidal activity of synthesized LaOF: Dy3+ (3 mol %) NS on

pathogenic bacteria with different concentration of A.V gel

Table 7: The A.V gel concentration dependent antifungal effect of synthesized LaOF: Dy3+ (3

mol %) NS against F oxysporum

2

(b) (a)

Figure.4 SEM images of LaOF: Dy3+ (3 mol %) NS synthesized with different sonication

times (a, b) 1 h, (c, d) 2 h, (e) 3 h, (f) 4 h, (g) 5 h and (h) 6 h with A.V gel (30 ml) and